Volker Oye

• Melo, Guilherme W.S. de; Hermanns, Reginald Leonhard Manfred; Bendle, Jacob M.; Grevemeyer, Ingo; Fiolleau, Sylvain & Cesca, Simone [Vis alle 12 forfattere av denne artikkelen] (2026). Earthquake-triggered cascading hazards under Arctic amplification. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 123(38). doi: 10.1073/pnas.2617210123. Fulltekst i vitenarkiv
• Turquet, Antoine Leo; Wüstefeld, Andreas; Baird, Alan F.; Iranpour, Kamran; Dichiarante, Anna Maria & Stokkan, Sindre [Vis alle 11 forfattere av denne artikkelen] (2026). NORFOX: An Experimental Fibre-Optic DAS Array for Seismo-Acoustic Monitoring in Norway. Pure and Applied Geophysics (PAGEOPH). ISSN 0033-4553. doi: 10.1007/s00024-026-04076-y. Fulltekst i vitenarkiv Vis sammendrag

  Distributed Acoustic Sensing (DAS) is a rapidly developing technology providing spatially dense data of great value for seismic and acoustic monitoring. This paper presents NORFOX, a dedicated DAS installation in southeastern Norway. NORFOX comprises a dedicated fibre-optic array with a geometry designed for earthquake and explosion monitoring. A defining feature of the site is its co-location with the NORES seismic and infrasound arrays, enabling direct comparison of DAS observations with conventional seismic and acoustic measurements. This multi-sensor configuration provides a controlled environment for benchmarking DAS data, and it paves the way for advanced, multi-physics wavefield modelling. NORFOX records various natural and anthropogenic seismo-acoustic signals, including earthquakes, explosions, aircraft, and thunder. The ultra-dense spatial sampling provided by DAS can complement traditional monitoring networks, including those used for nuclear-test monitoring. NORFOX helps address key challenges in small-yield event detection, phase discrimination, and event classification. We describe the DAS array layout, the design rationale, the co-located instrumentation, and provide an initial characterisation of fibre performance and background noise behaviour. We also discuss practical aspects of operating the site and outline current limitations. The site is further complemented by an all-sky camera and weather station to record visual events such as meteoroids and lightning activity, and to measure environmental changes; both of which can support the interpretation of the DAS measurements. Using representative examples, we demonstrate the capability of NORFOX for DAS-based array analysis and benchmarking against conventional arrays. NORFOX therefore provides a valuable test-bed for developing, validating and comparing future DAS monitoring approaches in seismology and seismo-acoustic sensing.

• Holmgren, Joanna; Kaven, J. Ole & Oye, Volker (2026). Rapid hydrothermal triggering of induced seismicity at the Coso geothermal field. Scientific Reports. 16(1), s. 7057–7057. doi: 10.1038/s41598-026-38146-x. Fulltekst i vitenarkiv
• Ghione, Federica; Palacios, Sergio Molina; Torabi, Anita & Oye, Volker (2025). Evaluating earthquake impacts in oslo, norway: a multi-method approach. Natural Hazards. ISSN 0921-030X. 121, s. 19781–19809. doi: 10.1007/s11069-025-07588-3. Fulltekst i vitenarkiv Vis sammendrag

  In this study, we conducted a comprehensive seismic risk assessment for Oslo (capital of Norway), integrating both deterministic and probabilistic approaches to capture a holistic view of potential earthquake impacts. Based on the field data from exposed major faults in the Oslo rift margin and historical earthquakes in this region, the deterministic analysis examined three scenarios: (i) an Mw 5.4 earthquake that occurred in 1904 in the Oslo rift zone; (ii) a hypothetical Mw 6.0 event on the east side of the rift zone (Østmarka event), and (iii) a hypothetical Mw 6.0 event along an exposed fault zone in the central rift zone (Nesodden event). Among the three scenarios, the Østmarka event resulted in the highest losses, while the 1904 scenario showed negligible impact. In both the Østmarka and the 475-year return period probabilistic scenarios, Sentrum and Frogner neighbourhoods consistently emerged as the most affected areas. This is primarily due to a combination of local soil conditions and the prevalence of unreinforced masonry buildings, highlighting the critical interplay between physical hazard and locally specific vulnerability associated with the neighbourhood’s particular characteristics. The combination of deterministic and probabilistic approaches offers a detailed and nuanced understanding of seismic risks in Oslo. The findings underscore the need for targeted mitigation efforts and preparedness strategies, particularly in neighbourhoods that are more susceptible to seismic risks. By integrating these comprehensive risk assessments, the study provides valuable insights into the uneven distribution of seismic risk across Oslo. The results aim to inform local authorities and policymakers, aiding in the development of effective strategies to enhance the resilience of the city’s infrastructure and population against future seismic events.

• Dichiarante, Anna Maria; Torgersen, Espen; Redfield, Thomas Fitzmaurice; Köhler, Andreas; Torabi, Anita & Svendby, Anne Kathrine [Vis alle 7 forfattere av denne artikkelen] (2025). Spectral Analysis of Topography as Proxy for Lineament Analysis. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 130(2). doi: 10.1029/2024JB029790. Fulltekst i vitenarkiv Vis sammendrag

  Spectral analysis (SA) for image processing, utilizing the Fast Fourier Transform (FFT), computes the 2D power spectrum to capture the amplitude of each frequency component of an image. Recent studies have applied SA on digital elevation models (DEMs) to characterize repetitive and spatially homogeneous landforms in terms of their orientation, frequency, and amplitude. Here, we advance the application of SA by introducing a new preprocessing step and an appropriate windowing function, tailored to analyze heterogenous and complex topographies and derive lineament spatial distributions. The validation of our approach involved two phases: (a) testing on synthetic images, and (b) application to a case study. The synthetic image validation illustrated the length-weighted characteristics of SA-derived rose diagrams and the robustness of the method, evidenced by a 99% similarity across 1,000 synthetically generated lineament networks. The case study consisted of three areas characterized by different topographic patterns within the Oslo region of Norway. The SA-derived results were compared to lineaments automatically extracted using a conventional peak-and-valley seeking algorithm that mimics manual tracing of lineaments inside a 3D map domain. The comparison showed similarity better than 90%. Lastly, we addressed a key pitfall of SA by locating signatures observed in the power spectrum on the map through cross-correlation (CC) of profiles. Although CC results are not consistently perfect, they provide a promising avenue for further development.

• Baird, Alan F.; Morten, Jan Petter; Oye, Volker & Bjørnstad, Steinar (2025). Ocean Space Surveillance and Real-Time Event Characterization Using Distributed Acoustic Sensing on Submarine Networks. Seismological Research Letters. ISSN 0895-0695. 96(2), s. 691–705. doi: 10.1785/0220240360. Fulltekst i vitenarkiv Vis sammendrag

  Distributed acoustic sensing (DAS) can be deployed on existing submarine fiber-optic cables to add long-range sensor capability to the cable infrastructure. In this article, we present the following: (1) observations and analysis of impulsive source events from long-term DAS measurements on a North Sea submarine telecommunications cable. The observations include local earthquakes originating in the crust below the cable, underwater explosions originating in the water column, an onshore explosion from the nearby coast, and examples of sonic booms from supersonic aircraft and a suspected meteor from the atmosphere. The analysis reveals how the signals from earthquakes and underwater/aerial explosions can be distinguished in the data domain based on their frequency and apparent velocity characteristics. (2) A processing workflow enabling real-time marine surveillance including detection and location of explosions in the water column. The processing is verified by corroborating local earthquakes and underwater explosions with independent data sources. We show that different types of waves can be identified including seismic body waves, hydroacoustic waves, and atmospheric infrasound waves coupled through the water column. Tracking the travel-time moveout along the nonstraight cable route allows for positioning of the source, which we demonstrate by migration stacking of the recorded signal. Signal processing suitable for real-time classification and source location is applied to the recorded data and shows how ocean space surveillance at scale can be realized.

• Kleine, Franz; Bruland, Charlotte; Wüstefeld, Andreas; Oye, Volker & Landrø, Martin (2025). Seismic signal characterization of snow avalanches using distributed acoustic sensing in Grasdalen, western Norway. Natural Hazards and Earth System Sciences. ISSN 1561-8633. 25(8), s. 2771–2782. doi: 10.5194/nhess-25-2771-2025. Fulltekst i vitenarkiv
• Bruland, Charlotte; Dichiarante, Anna Maria; Köhler, Andreas; Oye, Volker; Bever, Ivan Van & Larose, Eric (2025). Cultural activity and impact of extreme weather events revealed by ambient seismic noise and perspective on quick clay failure monitoring in Oslo, Norway. Engineering Geology. ISSN 0013-7952. 347. doi: 10.1016/j.enggeo.2025.107936. Fulltekst i vitenarkiv Vis sammendrag

  The study of urban seismic noise offers various approaches to monitor cities, from source identification to structural investigations. We demonstrate its potential to monitor cultural activity and quick clay failure in Oslo, Norway using low-cost seismic sensors. We identify train passages, a rock concert, construction blasts, local earthquakes and a meteor. To retrieve seismic velocity variations in the near subsurface, we apply seismic interferometry to three years of urban noise (1–4 Hz) recorded at four sensors, two in a quick clay risk area. Despite urban noise variability, we obtain stable noise correlation functions using 1-day-stacks. The extracted velocity variations reveal changes in the ground due to freezing and thawing as well as due to pore pressure variations related to snowmelt and rainfall. Along with anti-correlation of velocity variations and pore pressure, we observe hysteresis associated to the soil’s water retention under different moisture conditions, which could provide insights into potential landslide hazard. A sharp velocity drop accompanying the heavy rainfall associated with an extreme weather event is observed. All these observations give us insights to what subsurface changes can be resolved and expected over longer time periods, which will allow us to identify unusual and permanent changes, e.g., related to quick clay. Theoretical dispersion curve analysis shows that lowering the velocity in a section of the sedimentary layer containing quick clay reduces surface wave velocities within the frequency range of interest. These results suggest that measuring velocity variations at our study site has the potential to detect quick clay instabilities

• Holmgren, Joanna; Kaven, Kaven Ole & Oye, Volker (2025). Long-Term Trends in Microseismicity During Operational Shut-Ins at the Coso Geothermal Field, California. The Seismic Record (TSR). 5(1), s. 73–82. doi: 10.1785/0320240041. Fulltekst i vitenarkiv
• Lindholm, Conrad; Bungum, Hilmar; Ghione, Federica; Meslem, Abdelghani; Huang, Chen & Oye, Volker (2025). Earthquakes and seismic hazard for Norway and Svalbard. Journal of Seismology. ISSN 1383-4649. 29, s. 107–126. doi: 10.1007/s10950-024-10270-z. Fulltekst i vitenarkiv Vis sammendrag

  We document a complete seismic hazard study for mainland Norway and the Svalbard archipelago. The study is based on a Probabilistic Seismic Hazard Analysis (PSHA) method, and for the first time a new earthquake catalogue is presented publicly that covers Norway, Svalbard and the adjacent offshore regions. The catalogue is developed from an extensive analysis of historical earthquakes combined with more recent instrumental data with 33864 reports between 1497 through 2018, and with magnitudes up to Mw 6.7. With this catalogue seismic hazard is computed for 10% exceedance in 475 years through a logic tree computation with 12 branches: two area-zonations, one zonation free branch and four GMPEs. These 12 branches were defined with the aim to reduce the model bias, i.e., to centre the model, and to capture the epistemic uncertainty of the results. While the conventional Vs30 reference velocity is usually around 800 m/s we have targeted a reference velocity of 1200 m/s, based on extensive documentation of Norwegian rock velocities. This has significant bearing on the calculated hazard and provides for results that better reflect the bedrock conditions in Norway. As a result of this, the predicted shaking intensities are lower than the values previously reported in the (1998) national building code. In the Supplementary Information we have provided a brief overview of the seismotectonic setting, some tests that further demonstrate the uncertainty in our hazard estimates, a model for H/V ground-motion response spectra, examples of the sensitivity to the bedrock reference velocity and a comparison between the present study and the ESHM20 results.

• Jerkins, Annie Elisabeth; Schweitzer, Johannes; Kettlety, Tom; Martuganova, Evgeniia; Kühn, Daniela & Oye, Volker (2025). Relocating seismic events in the North Sea: challenges and insights for earthquake analysis. Geophysical Journal International. ISSN 0956-540X. 241(1), s. 728–742. doi: 10.1093/gji/ggaf068. Fulltekst i vitenarkiv Vis sammendrag

  In this paper, we present a catalogue of relocated seismic events in the North Sea spanning 1961 to 2022. Data from all relevant agencies were combined, incorporating all available seismic phase readings, thereby enhancing station coverage. As a result, our updated locations reveal a more clustered and aligned seismicity pattern compared with the original catalogue. Even with our combined data set, only 157 of the 7089 relocated events have azimuthal gaps of less than 90 deg. Additionally, the distances between onshore stations and offshore events are considerable. Both of these factors lead to relatively poorly constrained hypocentres for most events. We therefore evaluate the performance of 1-D velocity models routinely used by different North Sea adjacent monitoring agencies for earthquake location estimations in the North Sea. The variations in assessments due to the seismic velocity model used are significantly larger than the uncertainty ellipses calculated in the relocation, demonstrating that arithmetic uncertainties systematically underestimate location uncertainties in this setting. Obtaining a realistic estimate of location uncertainty is however crucial, particularly for distinguishing between natural and induced seismicity. This is fundamental to safe monitoring of the North Sea offshore industries, including geological storage. To overcome these discrepancies between the uncertainty ellipses and our multiple relocations, we introduce an alternative method that accounts for variability in the 1-D velocity models. This approach enhances the reliability of the earthquake catalogue, and provides a more robust assessment of seismic activity in the North Sea.

• Goertz-Allmann, Bettina; Langet, Nadege; Iranpour, Kamran; Kühn, Daniela; Baird, Alan F. & Oates, Steve [Vis alle 10 forfattere av denne artikkelen] (2024). Effective microseismic monitoring of the Quest CCS site, Alberta, Canada. International Journal of Greenhouse Gas Control. ISSN 1750-5836. 133. doi: 10.1016/j.ijggc.2024.104100. Fulltekst i vitenarkiv
• Köhler, Andreas; Myklebust, Erik Bryhn; Dichiarante, Anna Maria & Oye, Volker (2024). Monitoring urban construction and quarry blasts with low-cost seismic sensors and deep learning tools in the city of Oslo, Norway. SEISMICA. 3(1). Fulltekst i vitenarkiv Vis sammendrag

  The aim of this study is to collect information about events in the city of Oslo, Norway, that produce a seismic signature. In particular, we focus on blasts from the ongoing construction of tunnels and under-ground water storage facilities under populated areas in Oslo. We use seismic data recorded simultaneously on up to 11 Raspberry Shake sensors deployed between 2021 and 2023 to quickly detect, locate, and classify urban seismic events. We present a deep learning approach to first identify rare events and then to build an automatic classifier from those templates. For the first step, we employ an outlier detection method using auto-encoders trained on continuous background noise. We detect events using an STA/LTA trigger and apply the auto-encoder to those. Badly reconstructed signals are identified as outliers and subsequently located using their surface wave (Rg) signatures on the seismic network. In a second step, we train a supervised classifier using a Convolutional Neural Network to detect events similar to the identified blast signals. Our results show that up to 87% of about 1,900 confirmed blasts are detected and locatable in challenging background noise conditions. We demonstrate that a city can be monitored automatically and continuously for explosion events, which allows implementing an alert system for future smart city solutions.

• Jerkins, Annie; Oye, Volker; Alvizuri, Celso; Halpaap, Felix Julian & Kværna, Tormod (2023). The 21 March 2022 M<inf>w</inf> 5.1 Tampen Spur Earthquake, North Sea: Location, Moment Tensor, and Context. Bulletin of The Seismological Society of America (BSSA). ISSN 0037-1106. 114(2), s. 741–757. doi: 10.1785/0120230163. Fulltekst i vitenarkiv Vis sammendrag

  The 21 March 2022 Mw 5.1 Tampen Spur earthquake is the largest event in the North Sea over the last 33 yr. The earthquake was recorded by a 10,708 sensors permanent reservoir monitoring system (PRM) deployed at the Snorre field only a few kilometers away from the epicenter. The event was also recorded on regional networks, as well as at teleseismic distances. Here, we take advantage of this large number of observations to relocate this seismic event, estimate a moment tensor, and refine the depth of the earthquake. The different data sets and location methods yield similar locations, suggesting a well‐constrained earthquake location with a depth of 22 ± 5 km. Furthermore, a moment tensor is estimated, which indicates a thrust fault mechanism. Deep crustal earthquakes (>20 km) have been documented within several continental rifts, for example, in Basin and Range in the United States and in northern Germany. Studying deep intraplate earthquakes such as the event observed here can offer insights into the rheology and structures in the deeper portions of the crust. This thrust earthquake implies the reactivation of an older fault in the lower crust consistent with the ridge‐push forces from the mid‐Atlantic ridge. Such brittle failure at depth indicates a lower crust with little to no fluids present at this depth within the Tampen Spur region.

• Rørstadbotnen, Robin Andre; Eidsvik, Jo; Bouffaut, Léa; Landrø, Martin; Potter, John Robert & Taweesintananon, Kittinat [Vis alle 15 forfattere av denne artikkelen] (2023). Simultaneous tracking of multiple whales using two fiber-optic cables in the Arctic. Frontiers in Marine Science. 10. doi: 10.3389/fmars.2023.1130898. Fulltekst i vitenarkiv Vis sammendrag

  Climate change is impacting the Arctic faster than anywhere else in the world. As a response, ecosystems are rapidly changing. As a result, we can expect rapid shifts in whale migration and habitat use concurrent with changes in human patterns. In this context, responsible management and conservation requires improved monitoring of whale presence and movement over large ranges, at fine scales and in near-real-time compared to legacy tools. We demonstrate that this could be enabled by Distributed Acoustic Sensing (DAS). DAS converts an existing fiber optic telecommunication cable into a widespread, densely sampled acoustic sensing array capable of recording low-frequency whale vocalizations. This work proposes and compares two independent methods to estimate whale positions and tracks; a brute-force grid search and a Bayesian filter. The methods are applied to data from two 260 km long, nearly parallel telecommunication cables offshore Svalbard, Norway. First, our two methods are validated using a dedicated active air gun experiment, from which we deduce that the localization errors of both methods are 100 m. Then, using fin whale songs, we demonstrate the methods' capability to estimate the positions and tracks of eight fin whales over a period of five hours along a cable section between 40 and 95 km from the interrogator unit, constrained by increasing noise with range, variability in the coupling of the cable to the sea floor and water depths. The methods produce similar and consistent tracks, where the main difference arises from the Bayesian filter incorporating knowledge of previously estimated locations, inferring information on speed, and heading. This work demonstrates the simultaneous localization of several whales over a 800 km area, with a relatively low infrastructural investment. This approach could promptly inform management and stakeholders of whale presence and movement and be used to mitigate negative human-whale interaction.

• Ghione, Federica; Köhler, Andreas; Dichiarante, Anna Maria; Aarnes, Ingrid & Oye, Volker (2023). Vs30 and depth to bedrock estimates from integrating HVSR measurements and geology-slope approach in the Oslo area, Norway. Frontiers in Earth Science. 11. doi: 10.3389/feart.2023.1242679. Fulltekst i vitenarkiv Vis sammendrag

  This work shows an alternative and efficient method to estimate Vs30 values and depth to basement data. The Vs30 value is the most important attribute to characterize the soil type and subsequently account for soil type related seismic amplification. We believe that these tools offer a powerful, non-invasive and cost-effective solution for obtaining accurate estimations of depth to basement. This approach is providing valuable information for seismic hazard assessments, geotechnical investigations and engineering design, as it can help estimate the amplification of ground motions during earthquakes, which is dependent on the soil properties and depth to bedrock. Overall, this study highlights the importance of understanding the geological and geotechnical characteristics of an area in order to accurately assess the seismic hazard and potential impacts of earthquakes. Those results can be used in earthquake hazard models and support decision-making processes related to land use planning, building codes, and emergency preparedness measures in earthquake-prone regions.

• Rodriguez, Ismael Vera; Isken, Marius Paul; Dahm, Torsten; Lamb, Oliver D; Wu, Sin-Mei & Kristjánsdóttir, Sigríður [Vis alle 20 forfattere av denne artikkelen] (2022). Acoustic Signals of a Meteoroid Recorded on a Large-N Seismic Network and Fiber-Optic Cables. Seismological Research Letters. ISSN 0895-0695. 94(2 A), s. 731–745. doi: 10.1785/0220220236. Fulltekst i vitenarkiv
• Ghione, Federica; Mæland, Steffen; Meslem, Abdelghani & Oye, Volker (2022). Building Stock Classification Using Machine Learning: A Case Study for Oslo, Norway. Frontiers in Earth Science. 10. doi: 10.3389/feart.2022.886145. Fulltekst i vitenarkiv
• Näsholm, Sven Peter; Iranpour, Kamran; Wüstefeld, Andreas; Dando, Benjamin; Baird, Alan F. & Oye, Volker (2022). Array Signal Processing on Distributed Acoustic Sensing Data: Directivity Effects in Slowness Space. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 127(2). doi: 10.1029/2021JB023587. Fulltekst i vitenarkiv Vis sammendrag

  Distributed Acoustic Sensing (DAS) involves the transmission of laser pulses along a fiber-optic cable. These pulses are backscattered at fiber inhomogeneities and again detected by the same interrogator unit that emits the pulses. Elastic deformation along the fiber causes phase shifts in the backscattered laser pulses which are converted to spatially averaged strain measurements, typically at regular fiber intervals. DAS systems provide the potential to employ array processing algorithms. However, there are certain differences between DAS and conventional sensors. While seismic sensors typically record the directional particle displacement, velocity, or acceleration, the DAS axial strain is inherently proportional to the spatial gradient of the axial cable displacement. DAS is therefore insensitive to broadside displacement, for example, broadside P-waves. In classical delay-and-sum beamforming, the array response function is the far-field response on a horizontal slowness (or wavenumber) grid. However, for geometrically non-linear DAS layouts, the angle between wavefront and cable varies, requiring the analysis of a steered response that varies with the direction of arrival. This contrasts with the traditional array response function which is given in terms of slowness difference between arrival and steering. This paper provides a framework for DAS steered response estimation accounting also for cable directivity and gauge-length averaging – hereby demonstrating the applicability of DAS in array seismology and to assess DAS design aspects. It bridges a gap between DAS and array theory frameworks and communities, facilitating increased employment of DAS as a seismic array, while providing building blocks for the development of DAS array design tools.

• Jerkins, Annie; Kohler, Andreas & Oye, Volker (2022). On the potential of offshore sensors and array processing for improving seismic event detection and locations in the North Sea. Geophysical Journal International. ISSN 0956-540X. 233(2), s. 1191–1212. doi: 10.1093/gji/ggac513. Fulltekst i vitenarkiv Vis sammendrag

  The capability to detect and locate seismicity in the North Sea is necessary to ensure the safety of future CO2 storage operations. Currently, the event location capabilities are hampered by a one-sided network configuration, as only sensors deployed on the Norwegian mainland are providing good signal-to-noise ratios. However, applying array processing techniques to groups of offshore sensors deployed at oil and gas reservoirs can improve the signal-to-noise ratio at such sites, which generally suffer from high noise contamination originating from platforms or seismic shooting. In this study we test the feasibility of array processing to sensors deployed at the Grane oil field to improve earthquake event locations. Out of the 3400 nodes installed, we have access to two data subsets: i) continuous data from 10 sensors spread out over the whole field, and ii) short segments of data from 30 sensors selected with the purpose to apply array methods. As the average interstation distance between the 10 sensors is 6 km, the recorded wavefield is not coherent and traditional array processing methods are not applicable. To optimize the usage of the 10-sensor offshore data for event location purposes, we develop a new method for incoherent array processing. We compute a characteristic function based on the kurtosis of the seismic traces prior to a frequency-wavenumber analysis. This method successfully determines slowness and back azimuth for almost all the evaluated earthquakes in this study. Using common coherent array processing, the 30 sensors show superior detection capabilities over the 10 sensors and will therefore decrease the detection threshold for seismic events in the region significantly if continuous data are available. We conclude that offshore sensors at Grane can be included as a part of a system for passive seismic monitoring in the North Sea. We recommend using the 30-sensors data for this purpose. However, as we only have access to continuous data from the 10 sensors in this study, we found that they are a good substitute when the 30-sensor data are not available.

• Zarifi, Zoya; Kohler, Andreas; Ringrose, Philip; Ottemöller, Lars; Furre, Anne-Kari & Hansteen, Fredrik [Vis alle 10 forfattere av denne artikkelen] (2022). Background Seismicity Monitoring to Prepare for Large-Scale CO<inf>2</inf> Storage Offshore Norway. Seismological Research Letters. ISSN 0895-0695. 94(2 A), s. 775–791. doi: 10.1785/0220220178. Fulltekst i vitenarkiv Vis sammendrag

  Prior to planned CO2 injection startup in the Horda platform offshore western Norway, in 2024, the Horda Network project has taken several measures to assess the potential of seismic hazard in the area. A study of the fault‐plane solutions in the Horda platform region confirms that the direction of maximum horizontal stress is dominantly northwest–southeast to east–west over the entire area. The relative stress ratio is higher in the southeast near the Norwegian craton and lower in the northwest. Analysis of the catalog of seismicity (in the period of 2001–2021) in the Horda platform region suggests a moderate rate of seismicity with a b‐value of ∼1. The magnitude of completeness is 1.5 (⁠ML⁠). One of the main challenges in monitoring offshore earthquakes in the Norwegian continental shelf (NCS) is the lack of azimuthal coverage when using the onshore permanent seismic stations from the Norwegian National Seismic Network (NNSN), located to the east of offshore events. To improve the azimuthal coverage, we integrated a limited number of offshore geophones from permanent reservoir monitoring systems of selected oil and gas fields (Grane and Oseberg on NCS) with the onshore NNSN seismic stations. This integration is challenging because of the level of ambient noise in the offshore geophones. To further improve the detection and location capability, we deployed a nine‐element onshore array of broadband seismometers (HNAR) on Holnsnøy island to the east of the Horda platform. By incorporating array processing methods on HNAR, the signal‐to‐noise ratio is improved, and several previously uncataloged earthquakes could be detected. Offshore sensors are often subject to correlated noise from seismic interferences and platform or shipping noise sources, so we also incorporated array processing for selected geophones from offshore deployments, which greatly reduced such noise and hence improved the event detection.

• Babarinde, Oladipupo; Stanchits, Sergey; Bauer, Robert; Frailey, Scott; Oye, Volker & Sweet, Dustin (2022). Relationships between fault characteristics and seismic responses in a large lab-scale tri-axial injection test conducted on a faulted Castlegate Sandstone. Journal of Structural Geology. ISSN 0191-8141. 162. doi: 10.1016/j.jsg.2022.104684. Fulltekst i vitenarkiv
• Park, Joonsang; Griffiths, Luke; Dautriat, Jérémie; Grande, Lars; Rodriguez, Ismael Vera & Iranpour, Kamran [Vis alle 16 forfattere av denne artikkelen] (2022). Induced-seismicity geomechanics for controlled CO<inf>2</inf> storage in the North Sea (IGCCS). International Journal of Greenhouse Gas Control. ISSN 1750-5836. 115. doi: 10.1016/j.ijggc.2022.103614. Fulltekst i vitenarkiv Vis sammendrag

  The aim of the current study, IGCCS (2017–2020), is to evaluate the feasibility of micro-seismic (MS) monitoring of CO2 injection into representative storage candidates in the North Sea, based on broad and quantitative characterization of relevant subsurface behavior with respect to geology, geomechanics and seismicity. For this purpose, we first group potential CO2 storage sites in the North Sea into three different depths. Then, advanced triaxial rock mechanical tests are performed together with acoustic emission (AE) acquisition under representative loading for CO2 storage sites in the North Sea and for formations of each depth group, covering shale, mudstone and sandstone cores. Our work focuses particularly on quantifying the effects of injected fluid type and temperature on mechanical behavior and associated MS response of subsurface sediments. The experiment results show that each depth group may behave differently in responses to CO2 injection. Particularly, the occurrence of detectable MS events is expected to increase with depth, as the combined effects of rock stiffness and temperature contrast between the host rock and injected CO2 are increasing. In addition, lithology plays an important role in terms of the MS response, i.e. high AE event rate is observed in sandstones, while aseismicity in shale and mudstone. The test results are then scaled up and applied to advanced coupled flow-geomechanics simulations and a synthetic field-scale MS data study to understand micro-seismicity at fracture, reservoir and regional scales. The numerical simulation of scCO2 injection scenario shows quite different stress-strain changes compared to brine injection, resulting mainly from the thermally-induced behavior. Furthermore, the numerical simulation study via so-called Cohesion Zone Modeling (CZM) approach shows strong potential to improve our understanding of the multiphase-flow-driven fracture propagation. Our synthetic MS data study, focused on slow-earthquake scenario, also suggests that sensors with high sensitivity at low frequency might be necessary for better signal detection and characterization during CO2 injection. This manuscript covers the main findings and insights obtained during the whole study of IGCCS, and refers to relevant publications for more details.

• Oye, Volker; Stanchits, Sergey; Babarinde, Oladipupo; Bauer, Robert; Dichiarante, Anna Maria & Langet, Nadege [Vis alle 8 forfattere av denne artikkelen] (2022). Cubic-meter scale laboratory fault re-activation experiments to improve the understanding of induced seismicity risks. Scientific Reports. 12(1). doi: 10.1038/s41598-022-11715-6. Fulltekst i vitenarkiv
• Kühn, Daniela; Shashidhar, Dodla; Rodriguez, Ismael Vera; Mallika, K.; Oye, Volker & Satyanarayana, H.V.S. (2021). Indo-Norwegian research collaboration on artificial water reservoir-triggered seismicity. First Break. ISSN 0263-5046. 39(4), s. 63–68. doi: 10.3997/1365-2397.fb2021030. Fulltekst i vitenarkiv
• Ringrose, Philip; Landrø, Martin; Potter, John; Eidsvik, Jo; Wienecke, Susann & Bouffaut, Léa [Vis alle 10 forfattere av denne artikkelen] (2021). Next generation geophysical sensing: exploring a new wave of geophysical technologies for the energy transition. First Break. ISSN 0263-5046. 39, s. 61–64. doi: 10.3997/1365-2397.fb2021076. Fulltekst i vitenarkiv
• Duboeuf, Laure; Oye, Volker & Dando, Benjamin (2021). An aggregated template methodology: Novel automatic phase-onset identification by template matching. Geophysical Prospecting. ISSN 0016-8025. 69(6), s. 1147–1166. doi: 10.1111/1365-2478.13103. Fulltekst i vitenarkiv Vis sammendrag

  The precision of P- and S-wave phase picking strongly determines the precision of earthquake locations, but such picking can be challenging in the case of emergent signals, large data sets or temporally varying seismic networks. To overcome these challenges, we have developed the concept of an aggregated template to perform automatic picking of the P- and S-wave phases. An aggregated template is defined as a representative event for a small area, built by aggregating the best signal-to-noise-ratio seismic traces from events with similar waveforms (i.e. multiplet events). A template matching procedure, based on the cross-correlation between an aggregated template and an unpicked event, automatically determines the unpicked event P- and S-wave phases. This method enables (1) consistent and accurate P- and S-wave phase picking and (2) reduces processing time relative to traditional template matching by using a clustering method that finds the most representative templates for a region, and thus limiting the required number of templates. We established two parameters to weight the picking precision: (1) the cross-correlation between the aggregated template and the unpicked event and (2) the number of P- and S-wave picks determined per event. We tested this method on 2100 events recorded in the south-west of Iceland. Nineteen aggregated templates have been defined and used to automatically pick ∼65% of the complete event catalogue with an accuracy within the range of the manual picking uncertainty. These automatically picked events can then be used for event location, even when characterized by low magnitude, low signal to noise ratios and with emergent P-wave signals.

Se alle arbeider i NVA

• Oye, Volker (2026). Nyhetssenter Vestland – NRK Vestland- Steinras slo ut på jordskjelvstasjonar. [Internet]. NRK Vestland. Fulltekst i vitenarkiv
• Oye, Volker; Langet, Nadege; Bogner, Laura; Bruland, Charlotte; Aspaas, Andreas Grøvan & Hadziioannou, Celine (2025). Decoding Instability: Linking Microseismicity Patterns, Deformation Monitoring and Ambient Seismic Noise at the Åknes Rock Slope”. Fulltekst i vitenarkiv
• Oye, Volker (2025). Case Studies on Induced Seismicity Related to Industrial-Scale CO2 Storage. Fulltekst i vitenarkiv
• Kiel, Antonia; Hadziioannou, Celine; Bruland, Charlotte; Bogner, Laura; Langet, Nadege & Oye, Volker (2025). Seismic Investigation of the &Aring;knes Rockslide: Using Ambient Seismic Noise to Identify Possible Rockslide Movement. doi: 10.5194/egusphere-egu25-7093. Fulltekst i vitenarkiv
• Goertz-Allmann, Bettina; Anders, Sven; Baird, Alan F.; Braun, Thomas; Fadil, Wardah & Gupta, Neeraj [Vis alle 17 forfattere av denne artikkelen] (2025). Microseismic monitoring and public perception of CCS – Lessons learned from the ENSURE project. Fulltekst i vitenarkiv
• Jerkins, Annie Elisabeth; Schweitzer, Johannes; Martuganova, Evgeniia; Kühn, Daniela & Oye, Volker (2025). A Relocated Earthquake Catalogue for the North Sea (1961–2022): Challenges and Insights for earthquake analysis. Fulltekst i vitenarkiv Vis sammendrag

  In this study, we present a newly compiled catalogue of relocated seismic events in the North Sea from 1961 to 2022. By combining phase data from multiple monitoring agencies, we improve station coverage, and our new locations reveal a more clustered and aligned seismicity pattern than in the original catalogue. However, most locations remain poorly constrained due to large azimuthal station gaps and significant event–station distances. Only 157 of 7089 events have azimuthal gaps smaller than 90 degrees. To evaluate the impact of these limitations, we examine how standard 1D velocity models—commonly used by monitoring agencies around the North Sea—affect event locations. We find that the choice of velocity model causes greater variation in hypocentre estimates than suggested by formal uncertainty ellipses, indicating that traditional methods often underestimate location error. This has important implications for distinguishing natural from induced seismicity, particularly in areas of offshore development such as CO₂ storage. To improve location reliability, we introduce a complementary relocation approach that incorporates model variability. This approach provides more realistic estimates of location uncertainty for seismic events in the North Sea.

• Jerkins, Annie Elisabeth; Köhler, Andreas & Oye, Volker (2025). Incoherent Seismic Array Processing Using Kurtosis: A Case Study from the Grane Oilfield. Fulltekst i vitenarkiv Vis sammendrag

  Seismic arrays are known for their superior detection capabilities compared to single sensors. Array processing techniques, such as FK analysis, can estimate slowness and back azimuth, improving earthquake location estimates. However, these techniques require signal coherence across the array. Factors such as geological conditions and sensor spacing can lead to signal incoherence. Several studies suggest that characteristic functions, such as STA/LTA or envelopes, can enhance signal coherence, making it possible to perform FK analysis. In this study, we test an alternative characteristic function for incoherent array processing: the kurtosis function. This methodology was developed using a seismic network deployed on the seabed at the Grane Oilfield, offshore Norway. The dataset consists of 10 sensors with significant spacing, which contributes to signal incoherence. Despite this challenge, the recursive kurtosis function enabled the estimation of slowness and back azimuth for 8 out of 10 tested events. Integrating these array parameters into earthquake location estimates revealed notable shifts in event positions. The method developed in this study has potential applications for IMS arrays, where signal coherence presents a significant challenge. For instance, it could be applied to arrays such as MJAR in Japan, which faces incoherent signals due to complex subsurface geology.

• Goertz-Allmann, Bettina; Baird, Alan F.; Fadil, Wardah; Iranpour, Kamran; Kühn, Daniela & Oye, Volker [Vis alle 7 forfattere av denne artikkelen] (2025). How do we best monitor induced seismicity of CCS sites? Fulltekst i vitenarkiv
• Bloch, Wasja; Drolet, Doriane; Plourde, Alexandre; Bostock, Michael & Oye, Volker (2025). Relative Moment Tensors Rejuvenated. doi: 10.5281/ZENODO.18153017. Fulltekst i vitenarkiv
• Bloch, Wasja; Oye, Volker; Drolet, Dorian; Bostock, Michael; Plourde, Alexandre & Kwiatek, Grzegorz (2025). Relative Moment Tensor Analysis of the DEEP Heat Enhanced Geothermal System, Finland. doi: 10.5281/ZENODO.18153471. Fulltekst i vitenarkiv
• Bloch, Wasja; Oye, Volker; Drolet, Doriane; Bostock, Michael; Plourde, Alexandre & Kwiatek, Grzegorz (2025). Relative Moment Tensor Analysis of the OTN3 Stimulation Seismicity: A new method for the micro-structural investigation of earthquake clusters. doi: 10.5281/ZENODO.18153724. Fulltekst i vitenarkiv Vis sammendrag

  We present the relMT algorithm to estimate relative seismic moment tensors (MT) of small seismic events and apply it to the 2018 stimulation seismicity of the DEEP EGS project in Espoo, Finland. Relative MTs are tied to an absolute reference MT. They can be computed for clustered events for which the subsurface Green’s function can be assumed equal and do not require detailed knowledge of the subsurface velocity structure. We triple the number of resolved MTs from 283 to 864 and lower the magnitude threshold to -0.5. Future developments of the algorithm promise to contribute consistent S-wave cross-correlation lag times to re-localization efforts.

• Oye, Volker (2025). NRK Nyheter 17:00 - NRK Nyheter - radio - NRK Radio. [Radio]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Hør hele NRK Radio sitt store utvalg av podkast, serier, dokumentarer, underholdning, film, sport og nyheter.

• Oye, Volker (2025). Kraftig jordskjelv i Myanmar – NRK Urix – Utenriksnyheter og -dokumentarer. [Internet]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Det er enorme øydeleggingar fleire stadar i Myanmar etter dei to jordskjelva: – Folk høyrer rop frå ruinane, fortel generalsekretær i CARE Noreg.

• Oye, Volker (2025). Massivt jordskjelv øst i Russland – NRK Urix – Utenriksnyheter og -dokumentarer. [Internet]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Kraftige jordskjelv i Øst-Russland utløste tsunamivarsel flere steder i Stillehavet. Dette varselet er nå avblåst flere steder.

• Oye, Volker (2025). Jordskjelv på Vestlandet: – Det var ganske skummelt – NRK Norge – Oversikt over nyheter fra ulike deler av landet. [Internet]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Fleire melder om merkbare ristningar i hus og bygningar på Vestlandet sundag kveld. Norsar varslar moglege etterskjelv

• http://www.tv2.no/ & Oye, Volker (2025). Tsunamivarsel: Russland truffet av fem meter høye bølger. [TV]. TV2. Fulltekst i vitenarkiv Vis sammendrag

  Natt til onsdag ble havet utenfor Russland rammet av det sjette kraftigste jordskjelvet som noensinne er målt.

• Oye, Volker (2025). Tsunamivarsel nedjusteres på Hawaii. [TV]. TV2. Fulltekst i vitenarkiv Vis sammendrag

  Hawaii vil ikke blir truffet av en større tsunami, slår varslingssenteret PTWC fast. Norske Sander forteller om kaos etter at det første varselet kom.

• Langet, Nadege; Bogner, Laura; Oye, Volker; Bruland, Charlotte; Hadziioannou, Céline & Aspaas, Andreas Grøvan (2025). Passive Seismic Monitoring of the Åknes Unstable Rockslope: Unveiling the Potential of Borehole Sensors. Fulltekst i vitenarkiv
• Ghione, Federica; Molina-Palacios, Sergio; Torabi, Anita & Oye, Volker (2024). Comprehensive Seismic Risk Assessment for Oslo (Norway): Integrating Deterministic and Probabilistic Approaches for Community-Specific Insights. Fulltekst i vitenarkiv
• Langet, Nadege; Oye, Volker; Aspaas, Andreas Grøvan; Lacroix, Pascal & Renard, François (2024). New insights on the Åknes rockslide (Norway) using borehole microseismic data. Fulltekst i vitenarkiv
• Ghione, Federica; Köhler, Andreas; Dichiarante, Anna Maria; Aarnes, Ingrid & Oye, Volker (2024). A new approach to estimate Vs30 and depth to bedrock: a case study from the Oslo area (Norway). Fulltekst i vitenarkiv
• Goertz-Allmann, Bettina; Baird, Alan F.; Fadil, Wardah; Iranpour, Kamran; Kühn, Daniela & Langet, Nadege [Vis alle 15 forfattere av denne artikkelen] (2024). Optimized Microseismic Event Detection and Source Analysis at the Quest CCS Site. Fulltekst i vitenarkiv
• Jerkins, Annie Elisabeth; Köhler, Andreas & Oye, Volker (2024). On the potential of offshore sensors and array processing for improving seismic event detection and locations in the North Sea. Fulltekst i vitenarkiv Vis sammendrag

  Ensuring the safety of oil and gas operations, as well as the future storage of CO2 in the North Sea, requires the effective detection and accurate location of earthquakes. However, the precise location of small-magnitude seismic events in Norway's offshore areas remains a considerable challenge. The primary difficulty stems from the large distances between seismic stations and the events, coupled with the fact that most sensors are located onshore, resulting in significant station gaps. This research explores how offshore sensors, typically utilised for continuous monitoring in oil and gas fields, can be employed to enhance earthquake location through advanced array processing techniques. Our study focuses on sensors deployed at the Grane oil field. From the 3,400 ocean bottom nodes deployed at Grane, we had ongoing access to data from 10 sensors and obtained specific data segments from a further 30 sensors. These 30 sensors were specifically selected to optimise traditional array processing techniques. In contrast, the 10 sensors, spaced 6 km apart, record incoherent signals, making standard array processing methods less effective. To address this challenge, we have developed a technique that uses the kurtosis characteristic function to improve signal coherence, allowing for effective frequency-wavenumber analysis. This new method has demonstrated promising results for most of the seismic events tested, enabling us to determine both apparent velocity and back azimuth. The 30 sensors, designed for conventional array processing, show significant potential in reducing the high levels of offshore noise, such as that generated by seismic surveys. This study highlights the potential of integrating offshore sensors with array processing techniques to improve the detection and location of seismic events in the North Sea and other regions

• Zarifi, Zoya; Köhler, Andreas; Ringrose, Philip; Oye, Volker; Jerkins, Annie Elisabeth & Bakke, Roger [Vis alle 13 forfattere av denne artikkelen] (2024). Baseline Monitoring of Seismicity to Prepare for Large-Scale CO2 Storage, Offshore Norway. Fulltekst i vitenarkiv Vis sammendrag

  The Horda platform located off the west coast of Norway hosts three large-scale CO2 storage licenses, with first CO2 injection planned to start in 2025 in the most developed site at EL001. Seismicity in this offshore region has been monitored by the Norwegian National Seismic Network (NNSN) based on mainland stations mostly to the east. The NNSN catalog, suggests a moderate rate of seismicity with a b-value of approximately 1 and a magnitude of completeness of M1.5 (Ml). However, the lack of azimuthal coverage of the NNSN seismic stations impacts the detection threshold and location accuracy of seismicity. Since 2018, the Horda NETwork (HNET) project has undertaken several measures to improve and optimize baseline seismicity monitoring in this region. These measures to enhance the detection threshold and improve location accuracy include integrating selected offshore geophones from the oil and gas Permanent Reservoir Monitoring systems with the NNSN stations, deploying a dedicated onshore array on Holsnøy island (HNAR array), deploying OBSs in the CO2 storage license around Aurora, and incorporating a 2.5D velocity model. In addition, the potential for using an existing telecommunication fiber optical cable for seismicity monitoring was tested, and the value of integrating different detectors (geophones, BroadBand seismometers, and fiber optic sensors) to enhance seismicity monitoring has been demonstrated. Furthermore, the HNET project has worked on improved communication with stakeholders by advancing a seismicity monitoring dashboard. This work demonstrates how costeffective solutions for seismicity monitoring offshore can be developed for CO2 storage sites, not only for this maturing project site but for prospective offshore storage sites elsewhere.

• Oye, Volker; Iranpour, Kamran; Kaschwich, Tina; Jerkins, Annie Elisabeth; Lind, Lars Wedde & Bolin, Håkan (2024). Smart Usage of Permanent Seismic Networks to Extract Forensic Evidence of Sudden Events. Proccedings European Association of Geoscientists and Engineers. 2024, s. 1-5–1-5. doi: 10.3997/2214-4609.2024101319. Fulltekst i vitenarkiv
• Redfield, Tim F.; Torgersen, Espen; Svendby, Anne Kathrine; Fabian, Karl Wilhelm Johannes; Dichiarante, Anna Maria & Oye, Volker (2024). Some thoughts on the usefulness of Lineament Maps. Fulltekst i vitenarkiv
• Dichiarante, Anna Maria; Redfield, Tim F.; Torgersen, Espen; Svendby, Anne Kathrine & Oye, Volker (2024). Spectral analysis as proxy for lineament spatial distribution: validation and case study. Fulltekst i vitenarkiv
• Bruland, Charlotte; Köhler, Andreas; Dichiarante, Anna Maria; Oye, Volker & Bever, Ivan Van (2024). Monitoring subsurface changes in a quick clay area during extreme weather. Fulltekst i vitenarkiv
• Holmgren, Joanna; Kaven, J. Ole & Oye, Volker (2024). Source Characteristics of Microseismicity Occurring During Operational Shut-in Periods at the Coso Geothermal Field, California. Fulltekst i vitenarkiv
• Holmgren, Joanna; Kaven, J. Ole & Oye, Volker (2024). Microseismicity at the Coso Geothermal Field, California. Fulltekst i vitenarkiv
• Jerkins, Annie Elisabeth; Oye, Volker; Alvizuri, Celso; Kværna, Tormod & Halpaap, Fellix (2024). The 21 March 2022 Mw 5.1 Tampen Spur Earthquake, North Sea: Location and depth determination. Fulltekst i vitenarkiv Vis sammendrag

  The Mw 5.1 earthquake on 21 March 2022 is the largest recorded earthquake in the North Sea over the last 33 years. The earthquake was felt all over Southern Norway as well as some parts of Scotland. The seismic event occurred a few kilometers from the Snorre field and was detected by its extensive network of nearly 10,708 sensors deployed for permanent reservoir monitoring. This seismic event was also recorded at both regional and teleseismic distances. In our study, we take advantage of the large number of recordings to determine the hypocenter and use regional stations to estimate its focal mechanism. To estimate the hypocenter, we use two main methods: first, estimating the hypocenter using the extensive Snorre PRM data alongside a local 1D model, incorporating a grid search approach; second, determining the location by combining local and regional P- and S-wave arrivals with teleseismic depth phases in a standard inversion process. Both datasets and methods give similar locations, showing a well-constrained earthquake location with a depth of 22 ± 5 km. We estimated the seismic moment tensor for the event using waveforms from regional broadband seismic stations, and the mechanism that best fits the observations points to a thrust type of event. This focal mechanism is consistent with the ridge-push forces from the Mid-Atlantic ridge. Thrust earthquakes at such depth in an intraplate setting are relatively uncommon, indicating that the lower crust in the region of the event is brittle.

• Jerkins, Annie Elisabeth; Oye, Volker & Köhler, Andreas (2024). On the potential of offshore sensors and array processing for improving seismic event detection and locations in the North Sea. Fulltekst i vitenarkiv Vis sammendrag

  The ability to detect and accurately locate seismic events is crucial for ensuring safe CO2 storage in the future. At present, accurately locating small-magnitude earthquakes offshore Norway is challenging. This is primarily due to the large distances between stations and events, and the onshore placement of sensors in Norway, causing significant azimuthal gaps. This study examines the use of offshore sensors installed at oil and gas reservoirs, intended for continuous reservoir monitoring, to enhance the precision of earthquake locations through array processing. In our research, we assess the potential of array processing with sensors deployed at the Grane oil field to improve earthquake event locations. From the 3,400 ocean bottom nodes installed, we utilised: (i) continuous data from 10 sensors and (ii) data segments from 30 sensors designated for array processing. The 10 sensors, spaced 6 km apart, record incoherent seismic signals, challenging traditional array methods. We develop a new method utilising the kurtosis characteristic function to make signals more coherent prior to performing frequency-wavenumber analysis. This approach successfully determined slowness and back azimuth for almost all earthquakes. The 30 sensors, suitable for regular array processing, greatly reduces noise from seismic shooting and other common offshore noise sources. This research underscores the value of array processing as a key tool in improving seismic event detection and locations in offshore environments.

• Larsen, T; Voss, Peter H.; Dahl-Jensen, Trine; Rinds, N; Lund, B. & Schmidt, P [Vis alle 15 forfattere av denne artikkelen] (2023). Analysis of the North Stream Underwater Blasts in the Baltic Sea on 26 September 2022. Fulltekst i vitenarkiv Vis sammendrag

  On 26 September, 2022 the International Monitoring System (IMS) detected two seismic events near the Danish island of Bornholm. The events were seen in both seismic and infrasound data and were located near the positions where large gas leaks from the North Stream were later observed. The events were furthermore recorded by seismographs in the surrounding countries and analysed at the National Data Centres. The waveforms exhibited clear properties of underwater blasts with significant P energy and much smaller S- energy, as well as other characteristics not associated with natural earthquakes. Further analysis revealed that particularly the second event may consist of multiple blasts close in time and space. Analysis of the events included integration between IMS data and regional data from Denmark, Sweden, Germany and Norway, and served as an exercise in collaboration during an international crisis.

• Maio, Florencia Victoria De; Stefano, Rita De; Valsecchi, Ruben; Bolletta, Fabio; Basso, Paolo & Cademartori, Marcello [Vis alle 12 forfattere av denne artikkelen] (2023). Assessment of current and future multi-risk interactions and cascading impacts across Europe: a case study in Oslo, Norway. Fulltekst i vitenarkiv
• Huang, Chen; Meslem, Abdelghani; Bolin, Håkan; Refsum, Vetle Kind; Kaschwich, Tina & Vezzoso, Alberto [Vis alle 10 forfattere av denne artikkelen] (2023). The TURNkey scientific engine, an advanced tool for earthquake disaster management. Fulltekst i vitenarkiv Vis sammendrag

  The TURNkey scientific engine is a useful tool for earthquake disaster management. Building upon state-of-the-art methodologies in seismic hazard assessment, risk evaluation and decision-support systems, the scientific engine effectively supports earthquake forecasting, early warning and rapid response actions. This study introduces the three main features of the TURNkey scientific engine. Through case studies, the unique services provided by the scientific engine to the stakeholders are demonstrated. It is shown that the engine improves situational awareness in operational earthquake forecasting (OEF), earthquake early warning (EEW), and rapid response to earthquake (RRE) and thus facilitates earthquake disaster management.

• Oye, Volker & Lycke, Anne Torunn Strømmen (2023). Hele halvøya måtte flykte. Så ble det stille. [Journal]. Aftenposten. Fulltekst i vitenarkiv Vis sammendrag

  I november var det stor fare for vulkanutbrudd på den islandske halvøya Reykjanes. Er faren like stor nå? For tre uker siden måtte rundt 4000 beboere i og rundt den lille byen Grindavik sørvest for Reykjavik evakuere fra hjemmene sine. Jordskjelvene og vulkanfaren på halvøya Reykjanes gjorde dem for farlige å bo i. Søndag 12. november var det rundt 2800 jordskjelv på halvøya. Men etter at både innbyggere og husdyr var trygt evakuert fra det lille tettstedet, har det vært stille rundt utbruddet. – Nå er det rundt ti jordskjelv pr. dag med en styrke på 2,2. Dette er nesten ikke til å kjenne, sier forskningsleder for Norsar, Volker Oye. Hvis denne dramatiske nedgangen på antall jordskjelv forsetter, kan de evakuerte kanskje flytte tilbake igjen, mener Oye.

• Köhler, Andreas; Alvizuri, Celso; Dando, Benjamin; Goertz-Allmann, Bettina; Schweitzer, Johannes & Oye, Volker [Vis alle 15 forfattere av denne artikkelen] (2023). Relative locations and moment tensors of the Nord Stream pipeline events. Fulltekst i vitenarkiv Vis sammendrag

  Two clear seismic events were observed on 26th September 2022 associated with the reported leaks from the Nord Stream 1 (Event 1, NE of Bornholm) and Nord Stream 2 pipelines (Event 2, SE of Bornholm). Arrivals of both events were detected and associated using data from several arrays in Norway and Finland, including the IMS stations NOA, FINES and ARCES. Additional signal analysis with data from the Swedish National Seismic Network and the Danish station on Bornholm enabled a third event to be identified. Auto-correlation analysis of the Event 2 revealed the third event (Event 2B) about 7 seconds after the main amplitude of the P onset (Event 2A). In contrast, for Event 1 SE of Bornholm no additional events could be identified from auto-correlation analysis, which increases confidence that these additional arrivals are not caused by interaction with geological structures. We also observe an arrival 7 s after the Pn phase before the Pg arrival on the NORES array. However, we cannot exclude that this onset interferes with the arrival of the PnPn phase. We then use the time differences between Event 2A and 2B measured by auto-correlation analysis on the Swedish and Danish network stations to determine relative epicentre locations. The results suggest that the two overlapping events occurred just about 220 m apart from each other. The relative locations fit very well with the distance between both pipelines of Nord Stream 1 at the Westernmost gas plume location (NE of Bornholm). We also estimated preliminary full moment tensors for Event 1 and 2 using seismic waveform data and analysed them on a source-type diagram. The results show positive isotropic parameters consistent with explosion-type mechanisms.

• Lund, B.; Eggertsson, G; Tryggvason, Ari; Schmidt, P.; Roth, Michael & Larsen, T.B. [Vis alle 17 forfattere av denne artikkelen] (2023). The Nord Stream underwater explosions: location, classification and yield estimation. Fulltekst i vitenarkiv Vis sammendrag

  Soon after midnight on 26 September 2022 the Swedish National Seismic Network, using data from Sweden, Denmark and Germany, automatically detected a seismic event in the Baltic southeast of the Danish island of Bornholm. The event was followed 17 hours later by a second, more complex, event northeast of Bornholm. The automatic locations of the events were within 6-9 km of later reported gas leaks in the Nord Stream 1 and 2 pipelines. Using recently developed, machine learning based, classifiers both events were automatically classified as explosions. Subsequent analysis of the second event revealed that it was in fact two blasts, separated by about 7 seconds. As the events occurred in the transition zone between the Fennoscandian Shield and the younger terranes of Denmark and northern Germany, 3D tomographic P- and S-velocity models were developed to improve locations and assess uncertainties, bringing the locations closer to the pipelines. Spectral analysis of the blast data show clear reverberations consistent with underwater explosions and a blast depth of approximately 75 m. The conclusion that the events are underwater blasts are further supported by data on known underwater explosions and a few earthquakes in the area. The magnitude of the first event was estimated at ML 1.9 and the combined second and third event had ML 2.3. Estimating the equivalent yield in the explosions is, however, non-trivial. Comparison to ground truth underwater explosions suggests yields of one to a few hundred kilos of equivalent TNT. The contribution to the seismic energy from suddenly outflowing methane gas is under investigation and results will be included in the presentation.

• Ghione, Federica; Köhler, Andreas; Dichiarante, Anna Maria & Oye, Volker (2023). Vs30 and depth to bedrock estimates using H/V measurements and geology and slope approach in the Oslo area, Norway. Fulltekst i vitenarkiv Vis sammendrag

  Common practice to perform a seismic hazard study at regional scale is to present the results computed at bedrock condition. Site effects are usually not considered because soil information is not always available. Our goal is to carry out a site-specific seismic hazard study for the city of Oslo (Norway), conducting a microzonation study that will include site effects. More specifically, the average shear wave velocity in the upper 30 meters of the ground (Vs30) has been introduced to become the main attribute to characterize the soil type and subsequently account for soil type related seismic amplification<p>Vs30 values are missing for the Oslo area, therefore we propose an integrated approach that estimates Vs30 using Horizontal-to-Vertical Spectral Ratio (HVSR) method together with a combined geology-slope approach. A campaign with 61 H/V measurements has been performed between March and June 2021 at specific locations in Oslo. Topographic slope attributed are extracted from DTM10 (10 m horizontal-scale r

• Oye, Volker (2023). Microseismic monitoring of storage sites. Fulltekst i vitenarkiv
• Oye, Volker (2023). Informal presentation of ENSURE. Fulltekst i vitenarkiv
• Jerkins, Annie; Köhler, Andreas & Oye, Volker (2023). On the potential of offshore sensors and array processing for improving seismic event detection and locations in the North Sea. Fulltekst i vitenarkiv Vis sammendrag

  CCS (Carbon Capture and Storage) is becoming an increasingly important technology to reduce global greenhouse gas emissions. The Norwegian part of the North Sea is an ideal place to conduct such projects as much of the infrastructure and experience is already in place due to current oil and gas operations. For safe CO2 storage an improved understanding of the natural background seismicity in the North Sea is still required. Currently, earthquakes in the region are monitored using onshore stations deployed on mainland Norway, resulting in low azimuthal sensor coverage and poorly constrained earthquake locations. However, permanent reservoir monitoring systems (PRMs), which are deployed offshore to surveil oil and gas fields, have the potential to reduce these station gaps and thus improve earthquake locations. In this study we test the potential of incorporating offshore sensors at the Grane oil field for earthquake locations and detection utilizing array processing techniques. The advantage of array processing is that it can enhance seismic signals, decrease the detection threshold, and put additional constraints on direction and apparent velocities. Out of the 3400 sensors deployed at the Grane field, we have access to two subsets of data: i) Continuous data from 10 sensors spread along the boundaries of the field and, ii) segments of data from 30 sensors optimized for the purpose of array processing. Since the distances between the 10 sensors are large (6 km), traditional array processing methods are not applicable, and we therefore test and develop a new method for incoherent array processing using the kurtosis characteristic function. The kurtosis function is applied to the seismic signal prior to FK-analysis to make the signal more coherent. The method showed great potential and worked for the majority of earthquakes analyzed in this study. The 30 sensor array was superior to the 10 sensor array and could potentially decrease the detection threshold of seismic events if continuous data are available. We conclude that the Grane sensors could be implemented as a part of a system for passive seismic monitoring in the North Sea. We recommend using the 30-sensors for this purpose. However, as we only have access to continuous data from 10 sensors, we found that these sensors are an appropriate replacement when the 30 sensors are not accessible.

• Oye, Volker (2023). Microseismic monitoring of storage sites. Fulltekst i vitenarkiv
• Huang, Chen; Bever, Ivan Van; Ibrahim, Osman Mohammad; Oye, Volker & Schweitzer, Johannes (2023). Multi-hazard risk-informed decision-support system: A case study in Oslo, Norway. Fulltekst i vitenarkiv
• Oye, Volker (2023). Microseismic monitoring of storage sites. Fulltekst i vitenarkiv
• Oye, Volker (2023). Monitoring of co2 storage sites- examples from the ACT project EBSURE. Fulltekst i vitenarkiv
• Oye, Volker (2023). Findings and ongoing studies on public perception. Fulltekst i vitenarkiv
• Oye, Volker (2023). Denne stjerna skal gi tryggere CO2-lagring. [Journal]. Geoforskning.no. Fulltekst i vitenarkiv
• Oye, Volker (2023). Monitoring and development of deep geothermal energy sites. Fulltekst i vitenarkiv
• Köhler, Andreas; Wüstefeld, Andreas; Baird, Alan F.; Dando, Benjamin; Svendsen, Guro Kristin & Iranpour, Kamran [Vis alle 8 forfattere av denne artikkelen] (2023). NORFOX versus NORES: A comparison of seismic events recorded on a co-located DAS and seismometer array. Fulltekst i vitenarkiv Vis sammendrag

  Distributed Acoustic Sensing (DAS) is becoming increasingly popular for different seismological applications due to its high spatial sampling and potentially long cable lengths. So far, the ability of DAS records for seismic array processing has not been assessed systematically with observed data. We use one month of continuous data recorded on the newly deployed NORFOX DAS array in southern Norway, which is co-located with the 16-element NORES broadband seismic array. NORES has a current aperture of approximately 1.4 km. NORFOX consists of a total cable length of approximately 8 km arranged in 5 arms, with an array aperture of 3 km. Data were acquired from three branches of the array using two DAS interrogators for the full month of February 2023. We analyze this unique data set by first comparing waveforms and signal to noise ratios (SNRs) of local, regional and teleseismic events detected on NORES with the DAS records. We then apply beamforming to the DAS data to evaluate SNR improvements for P and S wave beams deployed for all recorded events. Finally, results of Frequency-Wavenumber analysis of NORFOX and NORES data are compared. We test the findings of a previous theoretical study on DAS array processing which considers the broadside sensitivity of the cable and give a final evaluation of the potential of using DAS arrays for continuous seismic monitoring.

• Larsen, T.B.; Voss, Peter H.; Dahl-Jensen, Trine; Rinds, N; Lund, B. & Schmidt, P [Vis alle 15 forfattere av denne artikkelen] (2023). Integrating IMS data in the analysis of the Nord Stream underwater blasts in the Baltic Sea. Fulltekst i vitenarkiv Vis sammendrag

  On September 26, 2022 the International Monitoring System (IMS) of the CTBTO detected two seismic events near the Danish island of Bornholm as reported in the Reviewed Event Bulletin (REB). In the REB phases include both seismic and infrasound data up to 1600 km away and the events are located near the positions where large gas leaks from the Nord Stream pipelines were also observed. The events were recorded clearly by the Danish seismograph network with the closest two seismographs located on Bornholm at distances of 40 – and 70 km. Furthermore, seismographs in the surrounding countries picked up the signals and data were analysed at the national data centers. The waveforms exhibited clear properties of underwater blasts with significant P-energy and much smaller S-energy, as well as other characteristics not associated with natural earthquakes. Further analysis revealed that the second event may consist of multiple blasts close in time and space. Analysis of the events included integration between IMS data and regional data from Denmark, Sweden, Germany and Norway, communication with CTBTO experts, and served as an exercise in collaboration during an international crisis.

• Oye, Volker (2022). Jordskjelvfare i Norge. Fulltekst i vitenarkiv
• Rodriguez, Ismael Vera; Dahm, Torsten; Isken, Marius Paul; Kraft, Toni; Lamb, Oliver D & Wu, Sin-Mei [Vis alle 18 forfattere av denne artikkelen] (2022). Multiphase observations of a meteoroid in Iceland recorded over 40 km of telecommunications cables and a large-N network. Fulltekst i vitenarkiv
• Goertz-Allmann, Bettina; Langet, Nadege; Baird, Alan F.; Oates, Steve; Rowe, Carrie & Harvey, Stephen [Vis alle 8 forfattere av denne artikkelen] (2022). Effective microseismic monitoring of the QUEST CCS site, Alberta, Canada. Fulltekst i vitenarkiv
• Oye, Volker; Goertz-Allmann, Bettina; Langet, Nadege; Dichiarante, Anna Maria & Kühn, Daniela (2022). New Concepts for Independent and Transparent Monitoring of CO2 Storage Verification. Fulltekst i vitenarkiv
• Oye, Volker & Langet, Nadege (2022). Microseismic monitoring of Åknes. Fulltekst i vitenarkiv
• Ghione, Federica; Oye, Volker & Köhler, Andreas (2022). Towards the implementation of site effects in a site- specific seismic hazard study for Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Common practice to perform a seismic hazard study at regional scale is to present the results computed at bedrock condition. Site effects are usually not considered because soil information is not always available. Our goal is to carry out a site-specific seismic hazard study for the city of Oslo (Norway), conducting a microzonation study that will include site effects. More specifically, the Vs30 value has been introduced to become the main attribute to characterize the soil type and subsequently account for soil type related seismic amplification. Vs30 values are missing for the Oslo area, therefore we aim to invert Horizontal-to-Vertical (H/V) spectral ratio of ambient seismic noise as a proxy for S-wave velocity (Vs) profiles. A campaign with 61 measurements has been performed between March and June 2021 at specific locations in Oslo. In addition to resulting Vs30 values, this method will also allow us to define depth to bedrock estimates, which will likely be required for an updated Eurocode. The Vs30 values extracted from H/V measurements are compared to the Vs30 estimates from topographic slope attributes extracted from DTM (Digital Terrain Model). This procedure is applied in specific areas in the Oslo urban environment that are susceptible to site effect amplifications.

• Ghione, Federica; Mæland, Steffen; Meslem, Abdelghani & Oye, Volker (2022). Building typologies for Norway: a case study for Oslo using machine learning. Fulltekst i vitenarkiv Vis sammendrag

  To evaluate potential human and economic losses in a seismic risk assessment, it is important to define an exposure model by defining building materials and characteristics. The common approach to develop an exposure model is to have a first overview of the area with Google Earth and to perform extensive fieldwork in representative areas of the city. This procedure is time and cost consuming, and it is also subject to personal interpretation. To mitigate these costs, a Convolutional Neural Network (CNN) is used to automatically identify the different building typologies in the city of Oslo, Norway, based on facade images taken from in-situ fieldwork and Google Street View. The present article attempts to categorize Oslo’s building stock in five main building typologies: timber (T), unreinforced masonry (MUR), reinforced concrete (CR), composite (steel reinforced concrete) (SRC) and steel (S). This method shows good results for timber buildings with 91% accuracy score, but only 41% for steel reinforced concrete buildings. These variations can be explained by differences in the number of labelled images for each typology, comprising the training data, and differences in complexity between typologies. This work is the first tentative to identify Norwegian building typologies: based on experts judgement, the five types observed in Oslo can be applicable at national level. In addition, this study shows that CNNs can significantly contribute in terms of developing a cost-effective exposure model.

• Oye, Volker; Langet, Nadege & Aspaas, Andreas Grøvan (2022). Geohazards, Norway, Åknes, rockslide, seismic monitoring. Fulltekst i vitenarkiv
• Näsholm, Sven Peter; Iranpour, Kamran; Wüstefeld, Andreas; Dando, Benjamin; Baird, Alan F. & Oye, Volker (2022). Array signal processing on distributed acoustic sensing data: directivity effects in slowness space. Fulltekst i vitenarkiv Vis sammendrag

  Distributed Acoustic Sensing (DAS) involves the transmission of laser pulses along a fiber-optic cable. These pulses are backscattered at fiber inhomogeneities and again detected by the same interrogator unit that emits the pulses. Elastic deformation along the fiber causes phase shifts in the backscattered laser pulses which are converted to spatially averaged strain measurements, typically at regular fiber intervals. DAS systems provide the potential to employ array processing algorithms. However, there are certain differences between DAS and conventional sensors. The current paper is focused on taking these differences into account. While seismic sensors typically record the directional particle displacement, velocity, or acceleration, the DAS axial strain is inherently proportional to the spatial gradient of the axial cable displacement. DAS is therefore insensitive to broadside displacement, e.g., broadside P-waves. In classical delay-and-sum beamforming, the array response function is the far-field response on a horizontal slowness (or wavenumber) grid. However, for geometrically non-linear DAS layouts, the angle between wavefront and cable varies, requiring the analysis of a steered response that varies with the direction of arrival. This contrasts with the traditional array response function which is given in terms of slowness difference between arrival and steering. This paper provides a framework for DAS steered response estimation accounting also for cable directivity and gauge-length averaging – hereby demonstrating the applicability of DAS in array seismology and to assess DAS design aspects. It bridges a gap between DAS and array theory frameworks and communities, facilitating increased employment of DAS as a seismic array.

• Dando, Benjamin; Iranpour, Kamran; Wüstefeld, Andreas; Näsholm, Sven Peter; Baird, Alan F. & Oye, Volker (2022). Designing the next generation of seismic arrays using fibre optic DAS. Fulltekst i vitenarkiv Vis sammendrag

  While seismic arrays have been in use since the 1950s and are currently a vital part of the IMS, they have fundamentally consisted of single or 3-component seismometers to measure the ground motion at a discrete set of locations known as the array elements. With the advent of Distributed Acoustic Sensing (DAS) within the last two decades, there is currently great interest in exploring the potential seismological applications. In contrast to traditional seismometers, DAS measures the deformation (e.g. strain-rate) along the length of a fibre optic cable with great flexibility in the number of measurements that can be taken and where they are taken along a given cable layout. Applying such technology to seismic arrays offers an exciting opportunity to design array configurations that were previously impractical with individual seismometers. However, the use of DAS requires special consideration of its unique signal characteristics, which include insensitivity of P-waves arriving broadside to the fibre optic cable. In this paper we present a design study for the installation of a new fibre optical cable at the site of the existing NORES seismic array in Norway – a 1.4 km aperture array located within a subarray of IMS station PS27 (NOA). We demonstrate through the modelling of DAS-specific array response functions how to optimize a new seismic array for regional seismic monitoring, highlighting the importance of incorporating DAS directivity effects. The final design will be installed in 2022 supplementing the current NORES array and will provide a unique data set that could lead to a new generation of DAS seismic arrays for both regional and global seismic monitoring.

• Oye, Volker & Ibrahim, Osman Mohammad (2022). Presentasjons tittel: Bruk av TURNkey utviklede metoder til andre naturfarer i Oslo regionen - Kvikkleireskred Alna. Fulltekst i vitenarkiv
• Oye, Volker (2022). Hva har vi fått ut av TURNkeyprosjektet? Fulltekst i vitenarkiv
• Oye, Volker (2022). Delte Equinor-data: Ekspert: Gir informasjon om norsk sokkel. [Journal]. Dagbladet. Fulltekst i vitenarkiv
• Dichiarante, Anna Maria; Oye, Volker & Bruland, Charlotte (2022). First results from passive seismic data at the Little Grand Wash Fault. Fulltekst i vitenarkiv
• Goertz-Allmann, Bettina; Langet, Nadege; Baird, Alan F.; Oates, Steve; Rowe, Carrie & Harvey, Stephen [Vis alle 8 forfattere av denne artikkelen] (2022). Effective microseismic monitoring of the QUEST CCS site, Alberta, Canada. Social Science Research Network (SSRN). Fulltekst i vitenarkiv
• Huang, Chen; Meslem, Abdelghani; Bolin, Håkan; Refsum, Vetle Kind; Kühn, Daniela & Kaschwich, Tina [Vis alle 8 forfattere av denne artikkelen] (2022). A synthetic case study using the turnkey scientific engine for earthquake disaster management. Fulltekst i vitenarkiv Vis sammendrag

  During the risk management process, multi-disciplinary information and data from various sources need to be integrated and promptly processed to assist the identified stakeholders (e.g., civil protection, emergency responders) to react at the earliest stage to earthquake events to reduce the direct and indirect impacts and consequences. The TURNkey scientific engine was developed for this purpose. The TURNkey scientific engine is a comprehensive software incorporating state-of-the-art methodologies in hazard assessment, risk evaluation and decision-support systems to enable earthquake forecasting, early warning, and rapid response actions. Through a synthetic case study, this paper illustrates that the scientific engine can update the seismic hazard estimates as well as the risk and loss estimation in near real-time, taking into account the instrumental data, Did-You-Feel-It reports and eyewitness reports. With the help of the scientific engine, the stakeholders can understand the impact and consequences of the damaging earthquake to facilitate emergency response.

• Alvizuri, Celso; Huang, Chen; Jerkins, Annie; Schweitzer, Johannes & Oye, Volker (2022). Source parameters and shakemap (PGV) for the Mag. 5 North Sea earthquake on 2022-03-21. Fulltekst i vitenarkiv
• Huang, Chen; Meslem, Abdelghani; Bolin, Håkan; Refsum, Vetle Kind; Kühn, Daniela & Kaschwich, Tina [Vis alle 8 forfattere av denne artikkelen] (2022). An overview of the scientific engine of the TURNkey platform. Fulltekst i vitenarkiv
• Oye, Volker (2022). Dagsrevyen 19:00 21.03.2022. [TV]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Intervju i NRK Dagsrevyen om jordskjelv i Nordsjøen kl. 06:32, 21.03.2022. fra 19:23-19:29

• Oye, Volker (2022). Intervju i Dagens NRKP1. [Radio]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Intervju i programmet Dagens om Jordskjelv i Nordsjøen kl. 06:32 21.03.2022. Intervju med Volker Oye.

• Oye, Volker (2022). Lokalen, Distriktsprogram, Rogaland NRK radio 21.03.2022. [Radio]. NRK. Fulltekst i vitenarkiv Vis sammendrag

  Intervju med Volker Oye hos NRK Rogaland om jordkjselvet i Nordsjøen 21.03.22 kl. 06:32

• Dichiarante, Anna Maria; Langet, Nadege; Bauer, R; Goertz-Allmann, Bettina; Williams-Stroud, Sherilyn & Kühn, Daniela [Vis alle 9 forfattere av denne artikkelen] (2021). Identifying geological structures through microseismic cluster and burst analyses complementing active seismic interpretation. Fulltekst i vitenarkiv

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