Volker Oye

• 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.
• 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. 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.

• 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. ISSN 2296-6463. 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.

• 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. ISSN 2296-7745. 10. doi: 10.3389/fmars.2023.1130898. Fulltekst i vitenarkiv
• Vera Rodriguez, Ismael; 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.
• 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. 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. 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.
• 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. ISSN 2296-6463. 10. doi: 10.3389/feart.2022.886145.
• 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. ISSN 2045-2322. 12(1). doi: 10.1038/s41598-022-11715-6.
• Park, Joonsang; Griffiths, Luke; Dautriat, Jérémie; Grande, Lars; Vera Rodriguez, Ismael & 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
• 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.

• Duboeuf, Laure; Dichiarante, Anna Maria & Oye, Volker (2021). Interplay of large-scale tectonic deformation and local fluid injection investigated through seismicity patterns at the Reykjanes Geothermal Field, Iceland. Geophysical Journal International. ISSN 0956-540X. 228(3), s. 1866–1886. doi: 10.1093/gji/ggab423.
• Dando, Benjamin; Goertz-Allmann, Bettina; Kühn, Daniela; Langet, Nadege; Dichiarante, Anna Maria & Oye, Volker (2021). Relocating microseismicity from downhole monitoring of the Decatur CCS site using a modified double-difference algorithm. Geophysical Journal International. ISSN 0956-540X. doi: 10.1093/gji/ggab255.
• 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
• Keilegavlen, Eirik; Duboeuf, Laure; Dichiarante, Anna Maria; Halldorsdottir, Sæunn; Stefansson, Ivar & Naumann, Marcel [Vis alle 11 forfattere av denne artikkelen] (2021). Hydro-mechanical simulation and analysis of induced seismicity for a hydraulic stimulation test at the Reykjanes geothermal field, Iceland. Geothermics. ISSN 0375-6505. 97, s. 1–16. doi: 10.1016/j.geothermics.2021.102223.
• Kühn, Daniela; Shashidhar, Dodla; Vera Rodriguez, Ismael; 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.
• Ottemöller, Lars; Michalek, Jan; Christensen, Jon Magnus; Baadshaug, Ulf; Halpaap, Felix Julian & Natvik, Øyvind [Vis alle 8 forfattere av denne artikkelen] (2021). UiB-NORSAR EIDA Node: Integration of Seismological Data in Norway. Seismological Research Letters. ISSN 0895-0695. 92(3), s. 1491–1500. doi: 10.1785/0220200369.
• 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
• Vera Rodriguez, Ismael; Mæland, Steffen; Oye, Volker; Kelley, M & Modroo, A (2020). Unsupervised learning of transient signals recorded during CO2 injection in a reef reservoir. First Break. ISSN 0263-5046. 38, s. 69–73. doi: 10.3997/1365-2397.fb2020029.
• Williams-Stroud, Sherilyn; Bauer, Robert; Oye, Volker; Stanek, Frantisek; Greenberg, Sallie E. & Langet, Nadege (2020). Analysis of Microseismicity and Reactivated Fault Size to Assess the Potential for Felt Events by CO2 Injection in the Illinois Basin. Bulletin of The Seismological Society of America (BSSA). ISSN 0037-1106. doi: 10.1785/0120200112.
• Langet, Nadege; Goertz-Allmann, Bettina; Oye, Volker; Bauer, Robert; Williams-Stroud, Sherilyn & Dichiarante, Anna Maria [Vis alle 7 forfattere av denne artikkelen] (2020). Joint Focal Mechanism Inversion Using Downhole and Surface Monitoring at the Decatur, Illinois, CO2 Injection Site. Bulletin of The Seismological Society of America (BSSA). ISSN 0037-1106. doi: 10.1785/0120200075.
• Dodla, Shashidhar; Vera Rodriguez, Ismael; Kothamasu, Mallika; Kühn, Daniela; Wilks, Matthew & Satyanarayana, HariVenkata Subramanya [Vis alle 7 forfattere av denne artikkelen] (2020). Relative locations of an earthquake sequence recorded during June 2017 on the Koyna–Warna borehole seismic network of Western India. Bulletin of The Seismological Society of America (BSSA). ISSN 0037-1106. 110(6), s. 3130–3138. doi: 10.1785/012020068.
• Griffiths, Luke; Dautriat, Jérémie; Vera Rodriguez, Ismael; Iranpour, Kamran; Sauvin, Guillaume & Park, Joonsang [Vis alle 13 forfattere av denne artikkelen] (2019). Inferring microseismic source mechanisms and in situ stresses during triaxial deformation of a North-Sea-analogue sandstone. Advances in Geosciences. ISSN 1680-7340. 49, s. 85–93. doi: 10.5194/adgeo-49-85-2019. Fulltekst i vitenarkiv Vis sammendrag

  Monitoring microseismic activity provides a window through which to observe reservoir deformation during hydrocarbon and geothermal energy production, or CO2 injection and storage. Specifically, microseismic monitoring may help constrain geomechanical models through an improved understanding of the location and geometry of faults, and the stress conditions local to them. Such techniques can be assessed in the laboratory, where fault geometries and stress conditions are well constrained. We carried out a triaxial test on a sample of Red Wildmoor sandstone, an analogue to a weak North Sea reservoir sandstone. The sample was coupled with an array of piezo-transducers, to measure ultrasonic wave velocities and monitor acoustic emissions (AE) – sample-scale microseismic activity associated with micro-cracking. We calculated the rate of AE, localised the AE events, and inferred their moment tensor from P-wave first motion polarities and amplitudes. We applied a biaxial decomposition to the resulting moment tensors of the high signal-to-noise ratio events, to provide nodal planes, slip vectors, and displacement vectors for each event. These attributes were then used to infer local stress directions and their relative magnitudes. Both the AE fracture mechanisms and the inferred stress conditions correspond to the sample-scale fracturing and applied stresses. This workflow, which considers fracture models relevant to the subsurface, can be applied to large-scale geoengineering applications to obtain fracture mechanisms and in-situ stresses from recorded microseismic data.

• Dando, Benjamin; Oye, Volker; Näsholm, Sven Peter; Zühlsdorff, Lars & Wüstefeld, Andreas (2019). Complexity in microseismic phase identification: full waveform modelling, traveltime computations and implications for eventlocations within the Groningen gas field. Geophysical Journal International. ISSN 0956-540X. 217(1), s. 620–649. doi: 10.1093/gji/ggz017. Vis sammendrag

  Determining accurate microseismic event locations at the Groningen gas field in the Netherlands has important implications for understanding the ongoing induced seismicity and its associated seismic hazard. To improve the depth constraint of the microseismicity, downhole monitoring arrays have been deployed in the central region of the Groningen field. The observed seismicity at these receivers is characterized by significant complexity in the waveforms, due to the high velocity contrasts that exist and the acquisition geometry. Reliably identifying and picking phases for use in earthquake location algorithms is therefore particularly challenging. Using a well constrained and highly detailed 3-D velocity model, we show how full waveform modelling can be used to understand the causes of the observed phase complexity. By identifying the different modelled phase arrivals in detail, we look to identify any systematic changes in waveform complexity with source location, to aid phase identification of the recorded downhole data. Theoretical traveltimes are often the foundation of earthquake location algorithms. We highlight the associated problems of their computation for the downhole monitoring setup for the Groningen model by complementing the full waveform simulations with traveltime computations and their associated ray paths from both an eikonal solver and using the wavefront construction method. We highlight large inconsistencies in the traveltimes, demonstrate the limitations and sensitivity of ray tracing in a layered velocity model, and show how the theoretical traveltimes do not equate with the dominant phase arrivals observed within the modelled waveforms. Finally, we propose an approach based on computing P- and S-wave traveltimes directly from the full waveform modelling, such that phase picking is based on an amplitude threshold rather than individual phase identification, which can also be adjusted for any given moment tensor.

• Dando, Benjamin; Oye, Volker; Näsholm, Sven Peter; Zühlsdorff, Lars; Kühn, Daniela & Wüstefeld, Andreas (2019). Complexity in microseismic phase identification: full waveform modelling, travel-time computations, and implications for event locations within the Groningen gas field. Geophysical Journal International. ISSN 0956-540X. 217, s. 620–649. doi: 10.1093/gji/ggz017.
• Vasco, Donald W; Bissell, Robert C.; Bohloli, Bahman; Daley, Thomas M.; Ferretti, Alessandro & Foxall, William [Vis alle 16 forfattere av denne artikkelen] (2018). Monitoring and Modeling Caprock Integrity at the In Salah Carbon Dioxide Storage Site, Algeria. I Vialle, Stéphanie; Ajo-Franklin, Jonathan & Carey, William J. (Red.), Geological Carbon Storage: Subsurface Seals and Caprock Integrity. American Geophysical Union (AGU). ISSN 9781119118657. s. 243–269. doi: 10.1002/9781119118657.ch12. Vis sammendrag

  The In Salah gas development project, initiated in 2004, involves the long‐term storage of waste carbon dioxide associated with natural gas production at several central Algerian fields. Long‐term plans were to store up to 17 million tons of carbon dioxide during the life of the program. The project at In Salah was a pioneering effort in several respects. One feature that distinguishes In Salah from several other industrial‐scale CO2 sequestration projects, such as Sleipner, Weyburn, Decatur, and Aquastore, is the generally smaller storage volume in terms of overall reservoir thickness and lower average porosities of around 15%. The unique features of the In Salah storage site point to the importance of wellbore, geophysical, and geochemical monitoring to ensure that the integrity of the storage complex is maintained both during and after injection. In 2005 a Joint Industry Project was set up, in an effort to use various geophysical, geochemical, and production techniques to monitor the fate of the injected carbon dioxide. Here we describe the efforts made to monitoring the fate of the injected carbon dioxide, the state of the caprock, the estimated outcome of the storage effort, and some of the uncertainties that remain.

Se alle arbeider i Cristin

• 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.
• 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.
• Bruland, Charlotte; Köhler, Andreas; Dichiarante, Anna Maria; Oye, Volker & Van Bever, Ivan (2024). Monitoring subsurface changes in a quick clay area during extreme weather.
• 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. 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.

• De Maio, Florencia Victoria; De Stefano, Rita; 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.
• Oye, Volker & Lycke, Anne Torunn Strømmen (2023). Hele halvøya måtte flykte. Så ble det stille. [Avis]. Aftenposten. 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.

• 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 . 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). Denne stjerna skal gi tryggere CO2-lagring. [Fagblad]. Geoforskning.no.
• Oye, Volker (2023). Findings and ongoing studies on public perception.
• Oye, Volker (2023). Monitoring of co2 storage sites- examples from the ACT project EBSURE.
• Oye, Volker (2023). Microseismic monitoring of storage sites .
• Oye, Volker (2023). Microseismic monitoring of storage sites .
• Oye, Volker (2023). Informal presentation of ENSURE .
• Oye, Volker (2023). Microseismic monitoring of storage sites .
• 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. 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.

• Köhler, Andreas; Wüstefeld, Andreas; Baird, Alan F.; Dando, Benjamin; Svendsen, Guro Kristin & Iranpour, Kamran [Vis alle 7 forfattere av denne artikkelen] (2023). NORFOX versus NORES: A comparison of seismic events recorded on a co-located DAS and seismometer array. 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. 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.

• 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. 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.

• 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. 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.

• Huang, Chen; Van Bever, Ivan; Ibrahim, Osman Mohammad; Oye, Volker & Schweitzer, Johannes (2023). Multi-hazard risk-informed decision-support system: A case study in Oslo, Norway.
• 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. 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 resolution Digital Terrain Model), provided by the Norwegian Mapping Authority agency. 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. This procedure is applied in specific areas in the Oslo urban environment that are susceptible to site effect amplifications.

• Oye, Volker (2023). Monitoring and development of deep geothermal energy sites.
• 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). ISSN 1556-5068.
• Vera Rodriguez, Ismael; 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.
• Oye, Volker & Ibrahim, Osman Mohammad (2022). Presentasjons tittel: Bruk av TURNkey utviklede metoder til andre naturfarer i Oslo regionen - Kvikkleireskred Alna.
• Oye, Volker; Goertz-Allmann, Bettina; Langet, Nadege; Dichiarante, Anna Maria & Kühn, Daniela (2022). New Concepts for Independent and Transparent Monitoring of CO2 Storage Verification .
• 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.
• Oye, Volker; Langet, Nadege & Aspaas, Andreas Grøvan (2022). Geohazards, Norway, Åknes, rockslide, seismic monitoring.
• Dichiarante, Anna Maria; Oye, Volker & Bruland, Charlotte (2022). First results from passive seismic data at the Little Grand Wash Fault.
• Oye, Volker (2022). Delte Equinor-data: Ekspert: Gir informasjon om norsk sokkel. [Avis]. Dagbladet.
• 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 .
• 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.
• 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. 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.

• Oye, Volker & Langet, Nadege (2022). Microseismic monitoring of Åknes.
• Oye, Volker (2022). Hva har vi fått ut av TURNkeyprosjektet? .
• Oye, Volker (2022). Jordskjelvfare i Norge.
• 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. 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.

• 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. 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.

• Ghione, Federica; Oye, Volker & Köhler, Andreas (2022). Towards the implementation of site effects in a site- specific seismic hazard study for Oslo . 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. 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 (2022). Dagsrevyen 19:00 21.03.2022. [TV]. NRK. Vis sammendrag

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

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

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

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

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

• Oye, Volker (2021). Roundtable conference on safe storage of CO2 .
• Langet, Nadege & Oye, Volker (2021). 15+ years of seismic monitoring at Åknes.
• Kühn, Daniela; Vera Rodriguez, Ismael; Shashidhar, Dodla; Satyanarayana, HariVenkata Subramanya & Oye, Volker (2021). A cross-correlation approach for relative locations of an earthquake sequence recorded on the Koyna-Warna borehole seismic network .
• Ghione, Federica & Oye, Volker (2021). On the implementation of site effects for the new Seismic Hazard Map of Norway: an Oslo area case study.
• Ghione, Federica & Oye, Volker (2021). Seismic hazard map, Norway, site amplification, Vs30.
• 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.
• Park, Joonsang; Griffiths, Luke; Dautriat, Jérémie; Grande, Lars; Vera Rodriguez, Ismael & Iranpour, Kamran [Vis alle 16 forfattere av denne artikkelen] (2021). Induced-seismicity geomechanics for controlled CO2 storage in the North Sea (IGCCS). SSRN Electronic Journal. doi: 10.2139/ssrn.3819665.
• Griffiths, Luke; Dautriat, Jérémie; Park, Joonsang; Vera Rodriguez, Ismael; Iranpour, Kamran & Sauvin, Guillaume [Vis alle 13 forfattere av denne artikkelen] (2021). The Influence of Super-critical CO2 Saturation on the Mechanical and Failure Properties of a North Sea Reservoir Sandstone Analogue. SSRN Electronic Journal. doi: 10.2139/ssrn.3818808.
• Ghione, Federica; Oye, Volker & Mortensholm, Hans Petter Laahne (2020). Combining the Øygarden Fault Zone and past seismicity to develop a Probabilistic Seismic Hazard Study for U-864 submarine wreck location, west of Fedje Island (Norway).
• Deghan-Niri, R; Oye, Volker; Wüstefeld, Andreas; Bakke, Roger; Wilks, Matthew & Furre, Anne-Kari [Vis alle 7 forfattere av denne artikkelen] (2020). Developing Approaches for Background Seismicity Monitoring of Potential CO2 Storage Sites in Horda Area Offshore Norway.
• Keilegavlen, Eirik; Stefansson, Ivar; Berre, Inga; Duboeuf, Laure; Dichiarante, Anna Maria & Halldorsdottir, Sæunn [Vis alle 7 forfattere av denne artikkelen] (2020). A simulation model for fracture reactivation accounting for thermo-hydro-mechanical forces with applications to geothermal systems.
• Griffiths, Luke; Park, Joonsang; Soldal, Magnus; Sauvin, Guillaume; Grande, Lars & Choi, Jung Chan [Vis alle 13 forfattere av denne artikkelen] (2020). Assessing the potential of microseismic monitoring of North Sea geological CO2 storage sites through laboratory testing.
• Dichiarante, Anna Maria; Köhler, Andreas; Oye, Volker; Ghione, Federica; Mæland, Steffen & Redfield, Thomas Fitzmaurice [Vis alle 8 forfattere av denne artikkelen] (2020). Towards real-time monitoring and multi-risk assessment using seismic/acoustic and remote sensing data in the Oslo region.
• Langet, Nadege & Oye, Volker (2019). Automated classification of seismic signals on the Åknes unstable rockslope, Norway. Vis sammendrag

  In Norway, glacial erosion has shaped the landscapes for thousands of years, creating very steep fjords over the western parts of the country. The steep flanks of the fjords are potentially unstable, and their collapse could generate local flood waves causing both infrastructure damages and casualties. The Åknes unstable rockslope has been well studied and instrumented over the past decades and a surface seismic network of eight three-component geophones has been operational since 2006. The large database (more than 70,000 detected events so far) has led to the implementation of an automated classifier in 2017, sorting the detections in local microseismic events, rockfalls, distant earthquakes, noise and electronic spikes. For that purpose, we extract 16 features from the seismic signals, describing them in terms of duration, shape and frequency content. We use a training set composed of about 350 manually-classified events for which we are quite confident, and which are equally distributed in proportions. We initially tested different classification algorithms and finally opted for a Random Forest composed of 30 trees. Our results show that the classifier is good at discriminating between clear microseimic events and rockfalls (these event types reflect direct movements on the slope and are therefore of particular importance for its monitoring), but also that there is a continuum and overlap represented by what we call noise. That means this class would deserve a more thorough analysis, which would in turn result in a more complex classifier. The current classifier runs in near-real time for each new event that is detected and contributes to an Early Warning System which includes other (non-seismic) data.

• Langet, Nadege; Oye, Volker; Privat, Pierre-Etienne & Renard, Francois (2019). Seismic monitoring of the Åknes rockslope: status and challenges.
• Langet, Nadege; Oye, Volker; Iranpour, Kamran; Blikra, Lars Harald & Kristensen, Lene (2019). Seismic monitoring of the Åknes rockslope, Norway.
• Dando, Benjamin; Oye, Volker; Goertz-Allmann, Bettina & Wüstefeld, Andreas (2019). Avoiding Pitfalls and Extracting Value: Lessons for Induced Seismicity Monitoring. Vis sammendrag

  We present case studies from microseismic monitoring including the Groningen gas field and the Decatur CCS site. We highlight often overlooked monitoring considerations including choice of location algorithm and waveform complexity, and demonstrate how modelling can avoid or mitigate the negative effects. Interpretation of microseismicity can lead to valuable insight into reservoir processes. However, to extract the most value, analyses must go beyond standard processing techniques. We show how combining waveform cross-correlation, full waveform modelling, travel-time and ray-path analysis, and relative relocation methods can provide the necessary constraints to deliver improved interpretations from microseismic data sets.

• Griffiths, Luke; Dautriat, Jérémie; Vera Rodriguez, Ismael; Iranpour, Kamran; Sauvin, Guillaume & Park, Joonsang [Vis alle 12 forfattere av denne artikkelen] (2019). Characterization of insitu stress from laboratory-scale microseismic data, relevant to North Sea reservoirs. Vis sammendrag

  Microseismic monitoring at sites such as hydrocarbon reservoirs, mines, and geological CO2 storage reservoirs, can inform on rock integrity, fault locations and geometries, and localised stress changes. For example, at CO2 injection sites, pressure changes may cause slip on pre-existing fractures, resulting in detectable induced seismicity, indicating the progression of the CO2 plume and the pressure front preceding it, and providing a means for assessing the risk of leakage. Moment tensors are commonly inferred from microseismic data and, if fault planes are known, stress and fault orientations may also be inferred. However, it is difficult to verify the results of these methods at the reservoir scale, where measurements of in-situ stresses are unavailable, and faults can be too small to be observed by seismic surveys. Here, we apply the above methods to laboratory scale microseismic events—Acoustic Emissions (AE), where the situations are well controlled. Namely, we know: how the stress is changing, and where and when the failure plane is developing. For this, we acquired and analysed AE data during the deformation of a sandstone sample (a material relevant to North Sea reservoirs) until formation of a through-going fracture, which we then reactivated.

• Vera Rodriguez, Ismael & Oye, Volker (2019). Assessment of a convolutional neural network for real-time location and moment tensor reporting.
• Vera Rodriguez, Ismael; Kühn, Daniela; Wilks, Matthew; Oye, Volker; Shashidar, D & Malika, K [Vis alle 7 forfattere av denne artikkelen] (2019). Correlation between seismicity and water level in the Koyna dam, India.
• Griffiths, Luke; Dautriat, Jérémie; Vera Rodriguez, Ismael; Iranpour, Kamran; Sauvin, Guillaume & Park, Joonsang [Vis alle 13 forfattere av denne artikkelen] (2019). Inferring microseismic source mechanisms and in situ stresses during triaxial deformation of a North-Sea-analogue sandstone. Advances in Geosciences. ISSN 1680-7340. doi: 10.5194/adgeo-49-85-2019.
• Dando, Benjamin; Goertz-Allmann, Bettina; Iranpour, Kamran; Kühn, Daniela & Oye, Volker (2019). Enhancing CO2 monitoring at the Decatur CCS site through improved microseismic location constraints.
• Cerasi, Pierre; Stroisz, Anna Magdalena; Sønstebø, Eyvind Frode; Stanchits, Sergey; Oye, Volker & Bauer, Robert (2019). MICROSEISMICITY IN CO2 SEQUESTRATION: A LABORATORY GEOMECHANICAL STUDY.
• Duboeuf, Laure; Oye, Volker; Berre, Inga & Keilegavlen, Eirik (2019). Induced seismicity in the Reykjanes geothermal reservoir, Iceland: seismic event monitoring, characterization and clustering.
• Duboeuf, Laure; Oye, Volker; Berre, Inga; Keilegavlen, Eirik & Dando, Benjamin (2019). Automatic picking for induced seismicity in Iceland using an EAT (Empirically Aggregated Template) methodology.
• Keilegavlen, Eirik; Stefansson, Ivar; Berre, Inga; Oye, Volker; Duboeuf, Laure & Dang, Hau Trung (2019). Enhancing Geothermal Reservoirs – Modelling and Analysis of Hydraulic and Thermal Stimulation.
• Griffiths, Luke; Park, Joonsang; Sauvin, Guillaume; Soldal, Magnus; Grande, Lars & Mondol, Nazmul Haque [Vis alle 13 forfattere av denne artikkelen] (2019). Microseismic monitoring of reservoir rock and cap rock integrity at North Sea geological CO2 storage sites: insights from acoustic emission testing. Geophysical Research Abstracts. ISSN 1029-7006.
• Goertz-Allmann, Bettina; Kühn, Daniela; Langet, Nadege; Jordan, Michael; Bauer, Robert & Oye, Volker [Vis alle 7 forfattere av denne artikkelen] (2018). Goertz-Allmann, B. P., Kuehn, D., Langet, N., Jordan, M., Bauer, R., Oye, V., & Greenberg, S. (2018). Using fluid-induced microseismicity for reservoir characterization at Decatur. Seismological Research Letters. ISSN 0895-0695.
• Wilks, Matthew; Oye, Volker; Thomas, Peter James & Kolltveit, Erling (2018). Moving Towards Phase-Sensitive DAS Interrogators for Improved Waveform Correlation and Advanced Microseismic Processing Workflows.
• Duboeuf, Laure; Oye, Volker; Berre, Inga & Keilegavlen, Eirik (2018). Induced seismicity in a geothermal reservoir: a case study in the Reykjanes peninsula in Iceland.

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