Valerie Maupin

• Ben-Mansour, Walid & Maupin, Valerie (2025). Optimizing data usage in regional body wave tomography by using asynchronous network data and relative sensitivity kernels: an example from Patagonia. Geophysical Journal International. ISSN 0956-540X. 244(2). doi: 10.1093/gji/ggaf436. Fulltekst i vitenarkiv Vis sammendrag

  A very frequent approach for studying lithospheric processes is to deploy temporary seismological networks in dedicated areas and to map the mantle structures with different approaches. One of them is the well-established relative traveltime body wave tomography. Different circumstances often lead to a non-uniform deployment of stations both in space and time, and a wish to combine data which have been acquired asynchronously. This is the situation in Patagonia where two distinct seismic experiments provide complementary seismic data over the region covering the Patagonia slab window. Combining these data in one regional relative body wave tomography is however problematic as the two data sets are a priori with respect to two different reference models. In this contribution, we show that the number of finite-frequency relative traveltime residuals varies very strongly from station to station for this data set, violating the assumption implicit in relative traveltime tomography of a unique reference model due to an even data distribution for all events. We demonstrate the superiority of the inversion using relative sensitivity kernels compared with a traditional approach with absolute kernels and event terms. A resolution test proves how this is crucial for resolving the important issue of the eastern extent of the slab window. In addition, we discuss potential issues related to interference of the direct phases with core phases when measuring finite-frequency traveltime residuals by cross-correlation of waveforms in necessarily relatively large time windows. We also briefly outline our preferred strategy for performing crustal correction, keeping in mind that finite-frequency residuals require frequency-dependent crustal corrections.

• Ben‐Mansour, Walid; Maupin, Valerie; Wiens, Douglas A. & Richter, Andreas (2025). Deep Source Regions for Back‐Arc Volcanism in the Patagonian Slab Window Imaged by Finite Frequency P and SH Body Wave Tomography. Geophysical Research Letters. ISSN 0094-8276. 52(17). doi: 10.1029/2025gl115915. Fulltekst i vitenarkiv Vis sammendrag

  The subduction of the Chile Ridge beneath South America beginning 12–16 Myr ago opened a gap in the subducting slab beneath southern Patagonia, which migrated northward and is located today at 46°S. Geodynamic processes associated with the slab window are poorly understood. Here we apply finite‐frequency P and SH body wave tomography to seismic data from several temporary arrays as well as regional stations to image seismic heterogeneities down to 650 km depth. The results show strong low velocity anomalies extending to 400 km depth beneath recent back‐arc volcanism between 46°S and 48°S, suggesting a link to thermal upwelling in the upper mantle. The southern edge of the Nazca slab extends aseismically down to at least 350 km. We also image low upper mantle seismic velocities beneath the Patagonia icefields, suggesting low viscosity modulates the patterns of uplift and horizontal deformation observed by GNSS.

• Wang, Yijun; Kiraly, Agnes; Conrad, Clinton Phillips & Maupin, Valerie (2025). Mantle Flow and Anisotropy in Subduction Zones: Modeling and Clustering of Olivine Textures. Geochemistry Geophysics Geosystems. 26(7). doi: 10.1029/2025gc012160. Fulltekst i vitenarkiv Vis sammendrag

  The mantle near Earth's subduction zones endures intense deformation that generates anisotropic rock textures. These textures can be observed seismically and modeled geodynamically, but the complexity of this deformation makes analyses of these textures difficult. In this study, we apply time‐series clustering analysis to tracers within subduction models, allowing for the identification of regions in the subduction zone with common deformation histories and olivine crystallographic‐preferred orientation development. We compare olivine texture evolution predicted using different methods in both retreating and stationary‐trench settings. Our results reveal distinct variations in olivine texture, indicating that both seismic and viscous anisotropy can exhibit substantial heterogeneity within the mantle wedge, sub‐slab, and subducting plate regions. For retreating trenches, olivine textures are strongest in the mid‐depth mantle wedge region about 200 km away from the trench between 100 and 300 km depth. Our study shows that trench‐normal olivine a ‐axis orientations dominate in the center of subduction zones. Toroidal flow around slab edges generates a mix of trench‐normal, trench‐parallel, and oblique fast seismic directions. Textures and anisotropy are stronger for the retreating trench model than for the stationary trench model since more deformation has been accumulated due to trench motion. These findings provide insights for interpreting seismic anisotropy in subduction zones and highlight the importance of considering texture heterogeneity, as characterized by clustering algorithms, when analyzing both geodynamic models and seismic observations of subduction zones.

• Zhang, Youyuan; Lu, Laiyu; Maupin, Valerie; Qin, Tongwei & Ding, Zhifeng (2025). Mapping 3D Sedimentary Structures with Joint Inversion of H/V Spectral Ratios and Multimode Dispersion Curves Derived from Ambient Noise—Application to the Xiong‘an New Area, China. Bulletin of The Seismological Society of America (BSSA). ISSN 0037-1106. 115(2), s. 619–645. doi: 10.1785/0120240174. Fulltekst i vitenarkiv Vis sammendrag

  We present a procedure to use ambient noise recordings to derive high‐resolution 3D S‐wave velocity models for sedimentary structures by joint inversion of phase velocity dispersion curves (DCs) and horizontal‐to‐vertical spectral ratios (HVSRs). This procedure is applied to seismological data from a network of 894 stations with a spacing of about 1 km located in the Xiong’an New Area (China), close to Beijing. To obtain the DCs, a Modified Correlation BeamForming method is used to process the noise at subarrays, which enables us to map directly the lateral variations of the phase velocity of the Rayleigh‐wave fundamental mode, first overtone, as well as fundamental Love wave, in the total frequency range of 0.3–3 Hz. HVSRs are derived in the frequency range 0.1–10 Hz from the computation of the directional energy density of the three components at each station based on the diffuse field assumption. By combining the DCs obtained by the array‐based method and the single‐station HVSR curves in a joint inversion, a high‐resolution 3D S‐wave velocity model of the study area is established down to 2 km depth. The model brings useful information for seismic hazard assessment as well as geothermal energy exploration. It reveals that the thickness of the sediments is highly correlated with the distribution of geologic structures such as highs and lows.

• Ramirez, Florence; Selway, Katherine; Conrad, Clinton Phillips; Maupin, Valerie & Smirnov, Maxim (2024). Lateral and radial viscosity structure beneath Fennoscandia inferred from seismic and magnetotelluric observations. Physics of the Earth and Planetary Interiors. ISSN 0031-9201. 351. doi: 10.1016/j.pepi.2024.107178. Fulltekst i vitenarkiv Vis sammendrag

  Fennoscandia is continuously uplifting in response to past deglaciation, termed glacial isostatic adjustment or GIA, and its mantle viscosity is well constrained from ice sheet and sea level data. Here, we compare those GIA-constrained viscosities for the Fennoscandian upper mantle with geophysically-constrained viscosities. We construct the upper mantle viscosity structure of Fennoscandia by inferring temperature and water content from seismic and magnetotelluric (MT) data. Using a 1-D MT model for Fennoscandian cratons together with a global seismic model, we infer an upper mantle viscosity (below 250 km) of ∼1021±2 Pa·s, which encompasses the GIA-constrained viscosities of 1020 − 1021 Pa·s. The GIA viscosities are better matched if the Fennoscandian upper mantle is a wet harzburgite or a dry pyrolite, where pyrolite is ∼10 times more viscous than harzburgite. Using the average temperatures and water contents for harzburgitic upper mantle, the GIA viscosities require 1–4 mm grain sizes indicating a diffusion creep regime. In northwestern Fennoscandia, where a high-resolution 2-D resistivity model is available, greater inferred mantle water content implies viscosities that are 10–100 times lower than those for the Fennoscandian Craton. Our work suggests that the combination of seismic and MT observations can improve upper mantle viscosity estimates, especially for regions with laterally-varying viscosity structures or where GIA constraints are not available. Although our method represents an important step forward, viscosity uncertainty can be further reduced by incorporating additional constraints on rock composition, grain size and mantle stress, as well as more accurate geophysical data, into the viscosity calculation.

• Mauerberger, Alexandra; Sadeghisorkhani, Hamzeh; Maupin, Valerie; Gudmundsson, Ólafur & Tilmann, Frederik (2022). A shear-wave velocity model for the Scandinavian lithosphere from Rayleigh waves and ambient noise - Implications for the origin of the topography of the Scandes mountain range. Tectonophysics. ISSN 0040-1951. 838. doi: 10.1016/j.tecto.2022.229507. Fulltekst i vitenarkiv
• Maupin, Valerie; Mauerberger, Alexandra & Tilmann, Frederik (2022). The Radial Anisotropy of the Continental Lithosphere From Analysis of Love and Rayleigh Wave Phase Velocities in Fennoscandia. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 127(10). doi: 10.1029/2022JB024445. Fulltekst i vitenarkiv Vis sammendrag

  Radial anisotropy (RA) in the upper mantle of the Fennoscandian Shield is analyzed by joint inversion of Love and Rayleigh wave phase velocities measured from recordings of teleseismic events at the ScanArray network. The phase velocities are measured by beamforming using three geographical subsets of the network as well as the full network. We analyze how different procedures for determining the phase velocities influence the final result and uncertainty. Joint inversion of the phase velocities in the period range 22–100 s reveals the presence of similar RA in the three subregions, with an average ξ value of about 1.05 in the subcrustal lithosphere down to at least 200 km depth. This corresponds to SH waves faster than SV by 2%–3%, a value very similar to those found in other continental regions. Considering this anisotropy together with other observables pertaining to seismic anisotropy in the area, we cannot propose a unique model satisfying all data. We can show, however, in which conditions different types of olivine crystallographic preferred orientations (CPOs) commonly observed in natural samples are compatible with the observations. CPO types associated with the preferred orientation of the a-axis, in particular the common A-type CPO, require a-axes dipping not more than 25° from the horizontal plane to explain our observations. AG-type CPO, characterized by preferred orientation of the b-axis and occurring in particular in compressional settings, can be considered as an interesting alternative interpretation of continental lithospheric anisotropy, provided the olivine b-axis is dipping by at least 60°.

• Bulut, N; Thybo, H & Maupin, Valerie (2022). Highly heterogeneous upper-mantle structure in Fennoscandia from finite-frequency P-body-wave tomography. Geophysical Journal International. ISSN 0956-540X. 230(2), s. 1197–1214. doi: 10.1093/gji/ggac107. Fulltekst i vitenarkiv Vis sammendrag

  SUMMARY We present a P-wave velocity model of the upper mantle, obtained from finite-frequency body-wave tomography, to analyse the relationship between deep and surface structures in Fennoscandia, one of the most studied cratons on the Earth. The large array aperture of 2000 km × 800 km allows us to image the velocity structure to 800 km depth at very high resolution. The velocity structure provides background for understanding the mechanisms responsible for the enigmatic and strongly debated high topography in the Scandinavian mountain range far from any plate boundary. Our model shows exceptionally strong velocity anomalies with changes by up to 6 per cent on a 200 km scale. We propose that a strong negative velocity anomaly down to 200 km depth along all of Norway provides isostatic support to the enigmatic topography, as we observe a linear correlation between hypsometry and uppermost mantle velocity anomalies to 150 km depth in central Fennoscandia. The model reveals a low-velocity anomaly below the mountains underlain by positive velocity anomalies, which we explain by preserved original Svecofennian and Archaean mantle below the Caledonian/Sveconorwegian deformed parts of Fennoscandia. Strong positive velocity anomalies to around 200 km depth around the southern Bothnian Bay and the Baltic Sea may be associated with pristine lithosphere of the present central and southern Fennoscandian craton that has been protected from modification since its formation. However, the Archaean domain in the north and the marginal parts of the Svecofennian domains appear to have experienced strong modification of the upper mantle. A pronounced north-dipping positive velocity anomaly in the southern Baltic Sea extends below Moho. It coincides in location and dip with a similar north-dipping structure in the crust and uppermost mantle to 80 km depth observed from high-resolution, controlled source seismic data. We interpret this feature as the image of a Palaeoproterozoic boundary that has been preserved for 1.8 Gy in the lithosphere.

• Maupin, Valerie (2021). Combining asynchronous data sets in regional body-wave tomography. Geophysical Journal International. ISSN 0956-540X. 224(1), s. 401–415. doi: 10.1093/gji/ggaa473. Fulltekst i vitenarkiv Vis sammendrag

  SUMMARY Regional body-wave tomography is a very popular tomographic method consisting in inverting relative traveltime residuals of teleseismic body waves measured at regional networks. It is well known that the resulting inverse seismic model is relative to an unknown vertically varying reference model. If jointly inverting data obtained with networks in the vicinity of each other but operating at different times, the relative velocity anomalies in different areas of the model may have different reference levels, possibly introducing large-scale biases in the model that may compromise the interpretation. This is very unfortunate as we have numerous examples of asynchronous network deployments which would benefit from a joint analysis. We show here how a simple improvement in the formulation of the sensitivity kernels allows us to mitigate this problem. Using sensitivity kernels that take into account that data processing implies a zero mean residual for each event, the large-scale biases that otherwise arise in the inverse model using data from asynchronous station deployment are largely removed. We illustrate this first with a very simple 3-station example, and then compare the results obtained using the usual and the relative kernels in synthetic tests with more realistic station coverage, simulating data acquisition at two neighbouring asynchronous networks.

• Mauerberger, Alexandra; Maupin, Valerie; Gudmundsson, Ólafur & Tilmann, Frederik (2021). Anomalous azimuthal variations with 360° periodicity of Rayleigh phase velocities observed in Scandinavia. Geophysical Journal International. ISSN 0956-540X. 224(3), s. 1684–1704. doi: 10.1093/gji/ggaa553. Fulltekst i vitenarkiv
• Thybo, Hans; Bulut, Nevra; Grund, Michael; Mauerberger, Alexandra; Makushkina, Anna & Artemieva, Irina M. [Vis alle 12 forfattere av denne artikkelen] (2021). Scanarray-a broadband seismological experiment in the baltic shield. Seismological Research Letters. ISSN 0895-0695. 92(5), s. 2811–2823. doi: 10.1785/0220210015. Fulltekst i vitenarkiv Vis sammendrag

  The ScanArray international collaborative program acquired broadband seismological data at 192 locations in the Baltic Shield during the period between 2012 and 2017. The main objective of the program is to provide seismological constraints on the structure of the lithospheric crust and mantle as well as the sublithospheric upper mantle. The new information will be applied to studies of how the lithospheric and deep structure affect observed fast topographic change and geological‐tectonic evolution of the region. The program also provides new information on local seismicity, focal mechanisms, and seismic noise. The recordings are generally of very high quality and are used for analysis by various seismological methods, including P‐ and S‐wave receiver functions for the crust and upper mantle, surface wave and ambient noise inversion for seismic velocity, body‐wave P‐ and S‐wave tomography for upper mantle velocity structure using ray and finite frequency methods, and shear‐wave splitting measurements for obtaining bulk anisotropy of the upper and lowermost mantle. Here, we provide a short overview of the data acquisition and initial analysis of the new data, together with an example of integrated seismological results obtained by the project group along a representative ∼1800‐km‐long profile across most of the tectonic provinces in the Baltic Shield between Denmark and the North Cape. The first models support a subdivision of the Paleoproterozoic Svecofennian province into

• Wang, Kaiming; Lu, Laiyu; Maupin, Valerie; Ding, Zhifeng; Zheng, Chen & Zhong, Shijun (2020). Surface Wave Tomography of Northeastern Tibetan Plateau Using Beamforming of Seismic Noise at a Dense Array. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 125:e2019JB018416(4). doi: 10.1029/2019JB018416. Fulltekst i vitenarkiv Vis sammendrag

  In traditional surface wave tomography based on seismic noise, 2D phase or group velocity distribution is obtained by performing pure-path inversion after extracting interstation velocities based on the noise cross-correlation function. In this paper, we show that 2D surface wave phase velocity maps of adequate quality can be obtained directly, without interferometry, by beamforming the ambient noise recorded at array of stations. This method does not require a good azimuthal distribution of the noise sources. The 2D surface wave phase velocity map is obtained by moving the subarrays within a larger dense network of stations. The method is illustrated with seismic noise recorded by over 600 stations of the ChinArray (Phase II). We obtain 2D Rayleigh wave phase velocity maps between 7 and 35 s in Northeastern (NE) Tibetan Plateau and adjacent regions that compare well with results obtained with other methods. The shear wave velocity model is then derived by inverting the phase velocity with depth. The model correlates well with geology and tectonics in NE Tibet. Two clear mid-to-low crustal low-velocity zones are observed at 15- to 35-km depth beneath the Songpan-Ganzi terrane and Northwestern Qilian Orogen, possibly facilitating lower crustal flow in this key region for the tectonic evolution of NE Tibet.

• Köhler, Andreas; Maupin, Valerie; Nuth, Christopher & Pelt, Ward Van (2019). Characterization of seasonal glacial seismicity from a single-station on-ice record at Holtedahlfonna, Svalbard. Annals of Glaciology. ISSN 0260-3055. 60(79), s. 23–36. doi: 10.1017/aog.2019.15. Fulltekst i vitenarkiv Vis sammendrag

  Glacial seismicity provides important insights into glacier dynamic processes. We study the temporal distribution of cryogenic seismic signals (icequakes) at Holtedahlfonna, Svalbard, between April and August 2016 using a single three-component sensor. We investigate sources of observed icequakes using polarization analysis and waveform modeling. Processes responsible for five icequake categories are suggested, incorporating observations of previous studies into our interpretation. We infer that the most dominant icequake type is generated by surface crevasse opening through hydrofracturing. Secondly, bursts of high-frequency signals are presumably caused by repeated near-surface crevassing due to high strain rates during glacier fast-flow episodes. Furthermore, signals related to resonance in water-filled cracks, fracturing or settling events in dry firn or snow before the melt season, and processes at the glacier bed are observed. Amplitude of seismic background noise is clearly related to glacier runoff. We process ambient seismic noise to invert horizontal-to-vertical spectral ratios for a sub-surface seismic velocity model used to model icequake signals. Our study shows that a single seismic sensor provides useful information about seasonal ice dynamics in case deployment of a network is not feasible.

• Slagstad, Trond; Maystrenko, Yuriy; Maupin, Valerie & Gradmann, Sofie (2018). An extinct, Late Mesoproterozoic, Sveconorwegian mantle wedge beneath SW Fennoscandia, reflected in seismic tomography and assessed by thermal modelling. Terra Nova. ISSN 0954-4879. 30(1), s. 72–77. doi: 10.1111/ter.12310. Fulltekst i vitenarkiv Vis sammendrag

  A channel‐like, low‐velocity zone in the lithospheric mantle beneath W Norway coincides spatially with the extension of a recently discovered 200 × 50 km granite batholith, which formed as a result of oceanic subduction beneath the SW Fennoscandian margin between 1.07 and 1.01 Ga. Based on results from numerical modelling, we argue that the low‐velocity zone, at least in part, reflects the thermal (radioactive) effects of the refertilized mantle wedge of this magmatic arc. The geological record in SW Fennoscandia suggests that active‐margin magmatism terminated as a result of rapid slab rollback and trench retreat starting at ca. 1 Ga. The rapid shift from active‐ to passive‐margin processes was probably critical in preserving the mantle wedge, and its identification can therefore shed light on how active‐margin processes terminated in ancient orogens. © 2017 John Wiley & Sons, Inc.

• Maupin, Valerie (2017). 3-D sensitivity kernels of the Rayleigh wave ellipticity. Geophysical Journal International. ISSN 0956-540X. 211(1), s. 107–119. doi: 10.1093/gji/ggx294. Fulltekst i vitenarkiv Vis sammendrag

  The ellipticity of the Rayleigh wave at the surface depends on the seismic structure beneath and in the vicinity of the seismological station where it is measured. We derive here the expression and compute the 3-D kernels that describe this dependence with respect to S-wave velocity, P-wave velocity and density. Near-field terms as well as coupling to Love waves are included in the expressions. We show that the ellipticity kernels are the difference between the amplitude kernels of the radial and vertical components of motion. They show maximum values close to the station, but with a complex pattern, even when smoothing in a finite-frequency range is used to remove the oscillatory pattern present in mono-frequency kernels. In order to follow the usual data processing flow, we also compute and analyse the kernels of the ellipticity averaged over incoming wave backazimuth. The kernel with respect to P-wave velocity has the simplest lateral variation and is in good agreement with commonly used 1-D kernels. The kernels with respect to S-wave velocity and density are more complex and we have not been able to find a good correlation between the 3-D and 1-D kernels. Although it is clear that the ellipticity is mostly sensitive to the structure within half-a-wavelength of the station, the complexity of the kernels within this zone prevents simple approximations like a depth dependence times a lateral variation to be useful in the inversion of the ellipticity.

• Bodin, Torunn; Leiva, J.; Romanowicz, Bart; Maupin, Valerie & Yuan, H. (2016). Imaging anisotropic layering with Bayesian inversion of multiple data types. Geophysical Journal International. ISSN 0956-540X. 206(1), s. 605–629. doi: 10.1093/gji/ggw124. Fulltekst i vitenarkiv
• Köhler, Andreas; Maupin, Valerie & Balling, Niels (2015). Surface wave tomography across the Sorgenfrei-Tornquist Zone, SW Scandinavia, using ambient noise and earthquake data. Geophysical Journal International. ISSN 0956-540X. 203(1), s. 284–311. doi: 10.1093/gji/ggv297. Fulltekst i vitenarkiv Vis sammendrag

  We produce a S-wave velocity model of the crust and upper mantle around the Sorgenfrei–Tornquist Zone, southern Scandinavia, by analysing ambient seismic noise and earthquake recordings on temporary and permanent regional network stations. In a first step, we perform tomographical inversion of surface wave dispersion data from seismic noise to obtain Rayleigh and Love wave phase-velocity maps from 3 to about 30 s period. Local dispersion curves are then combined with regionally averaged surface wave velocities from earthquake data measured between 15 and about 100 s period. Dispersion curves are jointly inverted for a 3-D model of the S-wave velocity and radial velocity anisotropy by using a combined Monte Carlo and linearized inversion approach. Results reveal significant crustal as well as uppermost mantle velocity variations at all depth levels. Upper crustal structural variations are mainly controlled by the thick sedimentary Danish Basin with both low S-wave velocities and high anisotropy. Despite of the known limited capability of surface wave inversion to constrain interface depths and model parameter trade-offs, obtained Moho depths are in good agreement with previous studies in the region. Marked crustal thinning is clearly revealed beneath the Danish Basin with a narrow transition to the thicker crust in Swedish shield areas. Despite very different crustal and morphological structures, Denmark and southern Norway both have similar well-defined upper-mantle low-velocity zones, interpreted as asthenosphere, starting a depth of about 100 km. Compared with southern Sweden, showing high upper-mantle velocities, characteristic for shields, velocities are reduced by 0.30–0.40 km s−1 (6–8 per cent) at the depth levels of 140–200 km and radial anisotropy of 2–4 per cent is observed. Our study confirms the importance of the Sorgenfrei–Tornquist Zone, as a very deep structural boundary, separating old, thick, cratonic Baltica lithosphere in southern Sweden from reworked and attenuated Baltica lithosphere in Denmark and southern Norway. This article was originally published in Geophysical Journal International. © 2015 Oxford University Press

• Atakan, Kuvvet; Bjerrum, Louise Wedderkopp; Bungum, Hilmar; Dehls, John F.; Kaynia, Amir M. & Keers, Henk [Vis alle 14 forfattere av denne artikkelen] (2015). The European plate observing system and the Arctic. Arctic: Journal of the Arctic Institute of North America. ISSN 0004-0843. 68(5), s. 1–7. doi: 10.14430/arctic4446. Fulltekst i vitenarkiv
• Maupin, Valerie & Kolstrup, Marianne Lanzky (2015). Insights in P- and S-wave relative traveltime tomography from analysing finite-frequency Fréchet kernels. Geophysical Journal International. ISSN 0956-540X. 202(3), s. 1581–1598. doi: 10.1093/gji/ggv239. Fulltekst i vitenarkiv
• Kolstrup, Marianne Lanzky & Maupin, Valerie (2015). Measuring and crust-correcting finite-frequency travel time residuals-application to southwestern Scandinavia. Solid Earth (SE). ISSN 1869-9510. 6(4), s. 1117–1130. doi: 10.5194/se-6-1117-2015. Fulltekst i vitenarkiv
• Kolstrup, Marianne Lanzky; Hung, Shu-Huei & Maupin, Valerie (2015). Multiscale, finite-frequency P and S tomography of the upper mantle in the southwestern Fennoscandian Shield. Geophysical Journal International. ISSN 0956-540X. 202(1), s. 190–218. doi: 10.1093/gji/ggv130. Fulltekst i vitenarkiv
• Maupin, Valerie (2014). Surface wave inversion. I Beer, Michael; Kougioumtzoglou, Ioannis A; Patelli, Edoardo & Au, Ivan Siu-Kui (Red.), Encyclopedia of Earthquake Engineering. Springer. ISSN 9783642361975. Fulltekst i vitenarkiv
• Pedersen, Helle; Debayle, Eric & Maupin, Valerie (2013). Strong lateral variations of lithospheric mantle beneath cratons - Example from the Baltic Shield. Earth and Planetary Science Letters. ISSN 0012-821X. 383, s. 164–172. doi: 10.1016/j.epsl.2013.09.024. Fulltekst i vitenarkiv
• Kolstrup, Marianne Lanzky & Maupin, Valerie (2013). A Proterozoic boundary in southern Norway revealed by joint inversion of P-receiver functions and surface waves. Precambrian Research. ISSN 0301-9268. 238, s. 186–198. doi: 10.1016/j.precamres.2013.10.004. Fulltekst i vitenarkiv
• Maupin, Valerie; Agostini, Alessandra; Artemieva, Irina; Balling, Niels; Beekman, Fred & Ebbing, Jørg [Vis alle 20 forfattere av denne artikkelen] (2013). The deep structure of the Scandes and its relation to tectonic history and present-day topography. Tectonophysics. ISSN 0040-1951. 602, s. 15–37. doi: 10.1016/j.tecto.2013.03.010. Fulltekst i vitenarkiv
• Köhler, Andreas; Weidle, Christian & Maupin, Valerie (2012). Crustal and uppermost mantle structure of southern Norway: results from surface wave analysis of ambient seismic noise and earthquake data. Geophysical Journal International. ISSN 0956-540X. 191(3), s. 1441–1456. doi: 10.1111/j.1365-246X.2012.05698.x. Fulltekst i vitenarkiv Vis sammendrag

  We use ambient seismic noise and earthquake recordings on a temporary regional network in southern Norway to produce Rayleigh and Love wave phase velocity maps from 3 to 67 s period. Local dispersion curves are then jointly inverted for a 3-D shear wave velocity model of the region. We perform a two-step inversion approach. First, a direct search, Monte Carlo algorithm is applied to find best fitting isotropic velocity depth profiles. Those profiles are then used as initial models for a linearised inversion which takes into account radial anisotropy in the shear wave structure. Results reveal crustal as well as uppermost mantle structures in the studied region. Velocity anomalies in the upper crust are rather small in amplitude and can in most parts be related to surface geology in terms of rock densities. Old tectonic units like the Oslo Graben (300–240 Ma) and the Caledonian nappes (440–410 Ma) are clearly imaged. Furthermore, we find clear indications for localized crustal anisotropy of about 3 per cent. Despite generally poor resolution of interface depths in surface wave inversion, we find lateral variation of crustal thickness in agreement with previous studies. We are able to confirm and locate the transition from a slow lithospheric upper mantle underneath southern Norway to a fast shield-like mantle towards Sweden. This article has been accepted for publication in Geophysical Journal International © 2012 The Authors Geophysical Journal International © 2012 RAS Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

• Köhler, Andreas; Weidle, Christian & Maupin, Valerie (2012). On the effect of topography on surface wave propagation in the ambient noise frequency range. Journal of Seismology. ISSN 1383-4649. 16(2), s. 221–231. doi: 10.1007/s10950-011-9264-5. Fulltekst i vitenarkiv Vis sammendrag

  Due to the increasing popularity of analyzing empirical Green’s functions obtained from ambient seismic noise, more and more regional tomographical studies based on short-period surface waves are published. Results could potentially be biased in mountainous regions where topography is not small compared to the wavelength and penetration depth of the considered waves. We investigate the effect of topography on the propagation of short-period Rayleigh waves empirically by means of synthetic data using a spectral element code and a 3-D model with real topography. We show that topography along a profile through the studied area can result in an underestimation of phase velocities of up to about 0.7% at the shortest investigated period (3 s). Contrary to the expectation that this bias results from the increased surface distance along topography, we find that this error can be estimated by local topographic contrasts in the vicinity of the receiver alone. We discuss and generalize our results by considering topographic profiles through other mountain ranges and find that southern Norway is a good proxy to assess the topography effect. Nevertheless, topographic bias on phase velocity measurements is in general not large enough to significantly affect recovered velocity variations in the ambient noise frequency range. © 2012 Springer Verlag

• Kolstrup, Marianne Lanzky; Pascal, Christophe & Maupin, Valerie (2012). What compensates the topography of southern Norway? Insights from thermo-isostatic modeling. Journal of Geodynamics. ISSN 0264-3707. 61, s. 105–119. doi: 10.1016/j.jog.2012.03.008. Fulltekst i vitenarkiv
• Lu, Laiyu; Chekroun, Mathieu; Abraham, Odile; Maupin, Valerie & Villain, Géraldine (2011). Mechanical properties estimation of functionally graded materials using surface waves recorded with a laser interferometer. NDT & E international. ISSN 0963-8695. 44(2), s. 169–177. doi: 10.1016/j.ndteint.2010.11.007. Fulltekst i vitenarkiv
• Köhler, Andreas; Weidle, Christian & Maupin, Valerie (2011). Directionality analysis and Rayleigh wave tomography of ambient seismic noise in southern Norway. Geophysical Journal International. ISSN 0956-540X. 184(1), s. 287–300. doi: 10.1111/j.1365-246X.2010.04830.x. Fulltekst i vitenarkiv Vis sammendrag

  We process seismic broad-band data from southern Norway by cross correlation of ambient seismic noise in view of getting a better image of the crustal structure in the area. The main data set sterns from the temporary MAGNUS network which operated continuously from 2006 September to 2008 June. Additionally, data from permanent stations of the National Norwegian Seismic Network, the NORSAR array and GSN stations in the region are used. We compute vertical component cross-correlation functions using 41 receivers for 3-month time windows. Evaluation of the azimuthal and temporal variation of signal-to-noise ratios (SNRs) and f—k analysis of data from NORSAR array between 3 and 25 s period shows that the dominant source areas of seismic noise are located to the west and north of the network during most of the measurement time, which corresponds well to the Norwegian coast line. During summer months, the SNRs decrease but the azimuthal distribution becomes more uniform between 7 and 12 s period, suggesting a more diffuse character of the wavefield. Primary ocean microseisms above 12 s show different dominant source azimuths during this time period compared to the winter months. Time—frequency analysis is applied to measure Rayleigh wave group velocity dispersion curves between each station pair for each 3-month correlation stack and the mean and variance of all dispersion curves is computed for each path. After rejection of low-quality data, a careful analysis shows that the group velocities are not biased by noise directionality. We invert the data for group velocity maps at period bands between 3 and 25 s. At short periods, we find an average Rayleigh wave group speed of about 3 km s-1 and velocity anomalies that correlate very well with local surface geology. While higher velocities (+5 per cent) can be associated with the Caledonian nappes in the central part of southern Norway, the Oslo Graben is reflected by negative velocity anomalies (-3 to -5 per cent). At longer periods, group velocities correlate well with the variation of Moho depths beneath southern Norway. This article has been accepted for publication in Geophysical Journal International © 2010 The Authors Geophysical Journal International © 2010 RAS RAS Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

• Tshering, Tashi; Bhasin, Rajinder Kumar; Olsson, Roger & Maupin, Valerie (2011). Numerical analysis of rock support interaction in tunnels in seismic regions. I Qian, Qihu & Zhou, Yingxin (Red.), Harmonising Rock Engineering and the Environment. CRC Press. ISSN 9780415804448. Fulltekst i vitenarkiv
• Maupin, Valerie (2011). Upper-mantle structure in southern Norway from beamforming of Rayleigh wave data presenting multipathing. Geophysical Journal International. ISSN 0956-540X. 185(2), s. 985–1002. doi: 10.1111/j.1365-246X.2011.04989.x. Fulltekst i vitenarkiv
• Weidle, Christian; Maupin, Valerie; Ritter, J.; Kværna, Tormod; Schweitzer, Johannes & Balling, N. [Vis alle 9 forfattere av denne artikkelen] (2010). MAGNUS-A Seismological Broadband Experiment to Resolve Crustal and Upper Mantle Structure beneath the Southern Scandes Mountains in Norway. Seismological Research Letters. ISSN 0895-0695. 81(1), s. 76–84. doi: 10.1785/gssrl.81.1.76. Fulltekst i vitenarkiv
• Weidle, Christian & Maupin, Valerie (2008). An upper-mantle S-wave velocity model for Northern Europe from Love and Rayleigh group velocities. Geophysical Journal International. ISSN 0956-540X. 175(3), s. 1154–1168. doi: 10.1111/j.1365-246X.2008.03957.x. Fulltekst i vitenarkiv
• Qin, YL; Capdeville, Y; Maupin, Valerie; Montagner, JP; Lebedev, S & Beucler, E (2008). SPICE benchmark for global tomographic methods. Geophysical Journal International. ISSN 0956-540X. 175(2), s. 598–616. doi: 10.1111/j.1365-246X.2008.03904.x. Fulltekst i vitenarkiv
• Bodin, T & Maupin, Valerie (2008). Resolution potential of surface wave phase velocity measurements at small arrays. Geophysical Journal International. ISSN 0956-540X. 172, s. 698–706. doi: 10.1111/j.1365-246X.2007.03668.x. Fulltekst i vitenarkiv Vis sammendrag

  The deployment of temporary arrays of broadband seismological stations over dedicated targets is common practice. Measurement of surface wave phase velocity across a small array and its depth-inversion gives us information about the structure below the array which is complementary to the information obtained from body-wave analysis. The question is however: what do we actually measure when the array is much smaller than the wave length, and how does the measured phase velocity relates to the real structure below the array? We quantify this relationship by performing a series of numerical simulations of surface wave propagation in 3-D structures and by measuring the apparent phase velocity across the array on the synthetics. A principal conclusion is that heterogeneities located outside the array can map in a complex way onto the phase velocities measured by the array. In order to minimize this effect, it is necessary to have a large number of events and to average measurements from events well-distributed in backazimuth. A second observation is that the period of the wave has a remarkably small influence on the lateral resolution of the measurement, which is dominantly controlled by the size of the array. We analyse if the artefacts created by heterogeneities can be mistaken for azimuthal variations caused by anisotropy. We also show that if the amplitude of the surface waves can be measured precisely enough, phase velocities can be corrected and the artefacts which occur due to reflections and diffractions in 3-D structures greatly reduced. This article has been accepted for publication in Geophysical Journal International © 2007 The Authors Journal compilation © 2007 RAS Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

• Lu, LY; Maupin, Valerie; Zeng, RS & Ding, ZF (2008). Scattering of surface waves modelled by the integral equation method. Geophysical Journal International. ISSN 0956-540X. 174, s. 857–872. doi: 10.1111/j.1365-246X.2008.03787.x. Fulltekst i vitenarkiv
• Maupin, Valerie & Park, J. (2007). Theory and observations - wave propagation in anisotropic media. I Schubert, Gerald (Red.), Treatise on geophysics. Elsevier. ISSN 9780444519283. s. 289–321. Fulltekst i vitenarkiv
• Maupin, Valerie (2007). Introduction to mode coupling methods for surface waves. Advances in Geophysics. ISSN 0065-2687. 48, s. 127–155. doi: 10.1016/S0065-2687(06)48002-X. Fulltekst i vitenarkiv
• Qin, Yilong; Capdeville, Yann; Maupin, Valerie & Montagner, Jean-Paul (2006). Synthetic dataset to benchmark global tomographic methods. EOS. ISSN 0096-3941. 87(46), s. 512–512. Fulltekst i vitenarkiv
• Pedersen, HA; Bruneton, M & Maupin, Valerie (2006). Lithospheric and sublithospheric anisotropy beneath the Baltic shield from surface-wave array analysis. Earth and Planetary Science Letters. ISSN 0012-821X. 244, s. 590–605. Fulltekst i vitenarkiv
• Maupin, Valerie; Garnero, Edward; Lay, Thorne & Fouch, Matthew J. (2005). Azimuthal anisotropy in the D" layer beneath the Caribbean. Journal of Geophysical Research (JGR). ISSN 0148-0227. 110(B08301). doi: 10.1029/2004JB003506. Fulltekst i vitenarkiv
• Garnero, Edward; Maupin, Valerie; Lay, Thorne & Fouch, Matthew J. (2004). Variable azimuthal anisotropy in Earth's lowermost mantle. Science. ISSN 0036-8075. 306, s. 259–261. Fulltekst i vitenarkiv
• Pettersen, Øyvind & Maupin, Valerie (2002). Lithospheric anisotropy on the Kerguelen hotspot track inferred from Rayleigh wave polarisation anomalies. Geophysical Journal International. ISSN 0956-540X. 149, s. 225–246. Fulltekst i vitenarkiv
• Maupin, Valerie (2002). The amplitude of the Love-Rayleigh discrepancy created by small-scale heterogeneities. Geophysical Journal International. ISSN 0956-540X. 150, s. 58–64. Fulltekst i vitenarkiv
• Souriau, Annie; Sylvander, Matthieu; Maupin, Valerie; Fels, Jean-Francois & Rigo, Alexis (2002). Enregistrements sismologiques de l'explosion sur le site de l'usine AZF (Toulouse, France). Comptes rendus Geoscience. ISSN 1631-0713. 334, s. 155–161. Fulltekst i vitenarkiv
• Maupin, Valerie (2001). A multiple-scattering scheme for modelling surface wave propagation in isotropic and anisotropic three-dimensional structures. Geophysical Journal International. ISSN 0956-540X. 146, s. 332–348. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Wu, Ru Shan; Maupin, Valerie & Dmowska, Renata (2007). Advances in wave propagation in heterogeneous earth. Elsevier. ISBN 9780120188505. 606 s. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Maupin, Valerie (2026). The ACH legacy in seismic tomography. Fulltekst i vitenarkiv Vis sammendrag

  Regional seismic body-wave tomography is a very common approach for studying lithospheric processes. The basic principle is to measure differences in arrival times of seismic waves generated by many distant earthquakes and recorded at a network of seismic stations. This is used to map the 3D seismic structure in the lithosphere beneath the stations network. This methodology was pioneered in Norway in 1977 by Aki, Christoffersson and Husebye, and is often referred to as ACH-tomography in reference to this paper. Their seminal paper use data recorded at the NORSAR array in the Hedmark region and establish a procedure for exploiting these data and produce a 3D model of the P-wave velocity beneath the stations down to 100km depth. I have had recently the opportunity to reread this paper in connection with methodological aspects of a seismic tomography of Patagonia in which I have been involved. I got deeply impressed by how careful and correct the mathematical developments are in this historical paper, but also how some of the assumptions and limitations they pose have been forgotten by their successors. Since Husebye, who was the NORSAR host for this work, passed away recently, I thought it was timely to highlight this major Norwegian contribution to geophysics. I will present a very incomplete and subjective summary of the legacy of this work. Aki , K. , Christoffersson, A. & Husebye, E., 1977. Determination of the three-dimensional seismic structure of the lithosphere, J. geophys. Res., 82 (2), 277–296.

• Wang, Yijun; Kiraly, Agnes; Conrad, Clinton Phillips & Maupin, Valerie (2025). Subduction dynamics and mantle anisotropy: modeling and clustering of olivine textures. Fulltekst i vitenarkiv Vis sammendrag

  The mantle near Earth's subduction zones experiences significant deformation, forming anisotropic rock textures. These textures can be detected using seismic methods and simulated in geodynamic models. This study employs time-series clustering to examine tracers in subduction models, identifying regions with similar deformation histories, olivine crystallographic-preferred orientation (CPO) development, and CPO-induced anisotropic viscosity. We compare the evolution of olivine textures predicted by various numerical methods (e.g. D-Rex, MDM, and MDM+AV) for both retreating and stationary trench subduction settings. Our modeling shows notable variations in olivine texture around the slab and as a function of subduction dynamics. These variations, which are illuminated by the clustering analysis, show that texture, seismic, and viscous anisotropy can vary greatly within the mantle wedge, sub-slab, and subducting plate regions of the upper mantle. In the retreating-trench model, the strongest textures are observed in the mid-depth mantle wedge region and beneath the slab at the 660 km transition zone. Trench-normal olivine a-axis orientations are predominant in the center of subduction zones, while toroidal flow around slab edges produces a mix of trench-normal, trench-parallel, and oblique fast seismic directions. On the other hand, in the stationary-trench model, the trench-normal signal in front of the slab is weaker while there are stronger trench-normal signals behind the slab at shallow depths between 100 and 300 km. At the edge of the slab, weak toroidal flow produces trench-oblique orientations while trench-parallel and trench-normal orientations are missing. In general, the retreating trench model exhibits stronger textures and anisotropy due to increased deformation from trench motion. These results provide valuable insights into seismic anisotropy in subduction zones and underscore the importance of considering texture heterogeneity when interpreting geodynamic models and seismic data. The use of time-series clustering algorithms highlights the intricate pattern of evolution and the relationship between deformation history, CPO, and CPO-induced viscous anisotropy occurring within subduction zones.

• Mansour, Walid Ben; Wiens, Douglas A & Maupin, Valerie (2024). Multi-scale, finite frequency body wave tomography with relative kernels. Fulltekst i vitenarkiv
• Mansour, Walid Ben; Wiens, Douglas A; Maupin, Valerie; Richter, Andreas; Hung, Shu-Huei & Barrientos, Sergio (2023). 3-D seismic velocity structure of the Patagonian slab from multi-scale finite frequency body wave tomography. Fulltekst i vitenarkiv
• Mansour, Walid Ben; Wiens, Douglas A; Mark, Hanna & Maupin, Valerie (2023). Physical Properties of the Mantle Beneath Patagonia From Surface and Body Wave Tomography. Fulltekst i vitenarkiv
• Ramirez, Florence Dela Cruz; Selway, Kate; Conrad, Clinton Phillips; Smirnov, Maxim & Maupin, Valerie (2023). Lateral and radial viscosity variations beneath Fennoscandia inferred from seismic and MT observations. Fulltekst i vitenarkiv
• Michalek, Jan; Atakan, Kuvvet; Ottermøller, Lars; Natvik, Øyvind; Lampe, Ove Daae & Fonnes, Gro [Vis alle 14 forfattere av denne artikkelen] (2023). EPOS-Norway Portal. Fulltekst i vitenarkiv
• Michalek, Jan; Atakan, Kuvvet; Ottermøller, Lars; Natvik, Øyvind; Langeland, Tor & Lampe, Ove Daae [Vis alle 15 forfattere av denne artikkelen] (2023). EPOS-Norway Portal. Fulltekst i vitenarkiv
• Michalek, Jan; Atakan, Kuvvet; Rønnevik, Christian; Indrøy, Helga; Ottermøller, Lars & Natvik, Øyvind [Vis alle 17 forfattere av denne artikkelen] (2021). EPOS-Norway Portal. Fulltekst i vitenarkiv
• Köhler, Andreas; Buscaino, Giuseppa; Lefeuvre, Pierre-Marie; Maupin, Valerie; Nuth, Christopher & Petlicki, Michal [Vis alle 7 forfattere av denne artikkelen] (2018). Seismic monitoring of glaciers and permafrost: What micro-seismicity and ambient noise can tell us about cryospheric processes in Svalbard. Fulltekst i vitenarkiv
• Köhler, Andreas; Buscaino, Giuseppa; Lefeuvre, Pierre-Marie; Maupin, Valerie; Nuth, Christopher & Petlicki, Michal [Vis alle 8 forfattere av denne artikkelen] (2018). Studying and quantifying glacier dynamics in Svalbard using cryoseismology. Fulltekst i vitenarkiv
• Gibbons, Steven John; Maupin, Valerie; Kolstad, Christian; Kværna, Tormod & Breivik, Asbjørn Johan (2018). Improved location estimates for seismicity along the northern North Atlantic Ridge. Fulltekst i vitenarkiv
• Weidle, Christian & Maupin, Valerie (2010). Imaging of surface wave phase velocities from array phase observations. Fulltekst i vitenarkiv
• Weidle, Christian; Asgedom, Endrias Getachew & Maupin, Valerie (2009). Regional surface wave tomographies for Northern Europe. Fulltekst i vitenarkiv
• Weidle, Christian; Maupin, Valerie; Ritter, Joachim; Wawerzinek, Britta; Kværna, T. & Schweitzer, J [Vis alle 9 forfattere av denne artikkelen] (2009). Mantle investigations of Norwegian Uplift Structure (MAGNUS) - a temporary broadband network in southern Norway. Fulltekst i vitenarkiv
• Weidle, Christian & Maupin, Valerie (2009). The ”rim of Baltica” at depth – the upper mantle beneath Northern Europe. Fulltekst i vitenarkiv
• Weidle, Christian & Maupin, Valerie (2009). Slow upper mantle beneath Southern Norway from surface waves. Fulltekst i vitenarkiv
• Weidle, Christian & Maupin, Valerie (2008). An upper mantle low-velocity finger from Iceland beneath southern Scandinavia – the key to understanding Neogene uplift? Fulltekst i vitenarkiv
• Weidle, Christian & Maupin, Valerie (2008). An upper mantle low-velocity finger from Iceland beneath southern Scandinavia – the key to understanding Neogene uplift? Fulltekst i vitenarkiv
• Weidle, Christian & Maupin, Valerie (2008). An upper mantle S-wave velocity model for Northern Europe from Love and Rayleigh group velocities. Fulltekst i vitenarkiv
• Weidle, Christian; Maupin, Valerie; Ritter, J.; Kværna, Tormod; Schweitzer, Johannes & Balling, N. [Vis alle 8 forfattere av denne artikkelen] (2008). Mantle investigations of Norwegian Uplift Structure (MAGNUS) – a temporary broadband network in southern Norway. Fulltekst i vitenarkiv
• Weidle, Christian; Maupin, Valerie; Ritter, J.; Kværna, T.; Schweitzer, Johannes & Balling, N. [Vis alle 8 forfattere av denne artikkelen] (2008). Mantle investigations of Norwegian Uplift Structure (MAGNUS) – a temporary broadband network in southern Norway. Fulltekst i vitenarkiv
• Weidle, Christian & Maupin, Valerie (2008). An upper mantle S-wave velocity model for northern Europe from love and Rayleigh group velocities. Fulltekst i vitenarkiv
• Weidle, Christian; Maupin, Valerie; Ritter, J.; Kværna, T.; Schweitzer, Johannes & Balling, N. [Vis alle 8 forfattere av denne artikkelen] (2007). MAGNUS (MAntle investiGations of Norwegian Uplift Structure) – a flying start into Topo Europe. Fulltekst i vitenarkiv
• Weidle, Christian & Maupin, Valerie (2007). Regional surface-wave tomography for Norway and adjacent regions. Fulltekst i vitenarkiv
• Weidle, Christian & Maupin, Valerie (2007). A Low-velocity Finger from Iceland beneath Southern Scandinavia - the Key to Understanding Neogene Uplift? Fulltekst i vitenarkiv
• Pedersen, Helle; Bruneton, Marianne & Maupin, Valerie (2005). Azimuthal and radial seismic anisotropy beneath the Baltic Shield. Fulltekst i vitenarkiv
• Qin, Yilong; Capdeville, Yann; Maupin, Valerie & Montagner, Jean-Paul (2005). A SPICE synthetic dataset to benchmark global tomographic methods. Fulltekst i vitenarkiv
• Maupin, Valerie (2004). Comment on 'The azimuthal dependence of surface wave polarization in a slightly anisotropic medium' by T. Tanimoto. Geophysical Journal International. ISSN 0956-540X. 159(1), s. 365–368. doi: 10.1111/j.1365-246X.2004.02390. Fulltekst i vitenarkiv
• Garnero, Edward; Maupin, Valerie; Lay, Thorne & Fouch, Matthew J. (2004). Seismological evidence for general anisotropy in the D" layer beneath the Caribbean. Fulltekst i vitenarkiv
• Maupin, Valerie (2004). Multiple scattering of surface waves in isotropic and anisotropic 3D structures. Fulltekst i vitenarkiv
• Maupin, Valerie (2004). Questions around the origin of the upper mantle transverse isotropy. Fulltekst i vitenarkiv
• Maupin, Valerie (2004). The nature of the D" layer: seismological constraints. Fulltekst i vitenarkiv
• Garnero, Edward; Maupin, Valerie; Lay, Thorne & Fouch, Matthew (2003). Complexities in D" anisotropy beneath the Caribbean: evidence for a tilted symmetry axis of transversely isotropic media from data and synthetics. Fulltekst i vitenarkiv
• Billien, Magali & Maupin, Valerie (2003). Waveform inversion of surface waves at geotechnical scale. Fulltekst i vitenarkiv
• Maupin, Valerie (2003). Surface waves in an heterogeneous anisotropic continental lithosphere. Fulltekst i vitenarkiv
• Pettersen, Oyvind & Maupin, Valerie (2003). Shear-coupled PL waves observed at the Kerguelen Isles. Fulltekst i vitenarkiv
• Maupin, Valerie (2002). Modelling surface wave propagation: recent advances and themes. Fulltekst i vitenarkiv
• Billien, Magali & Maupin, Valerie (2001). Caracterisation de la rigidite des sols par l'utilisation de sismique d'onde de surface. Fulltekst i vitenarkiv
• Pettersen, Øyvind & Maupin, Valerie (2001). Rayleigh wave polarisation anomalies reveal lithospheric anisotropy at the Kerguelen hotspot. Fulltekst i vitenarkiv
• Maupin, Valerie (2001). Anisotropy and the polarisation of seismic waves. Fulltekst i vitenarkiv
• Maupin, Valerie (2001). Small-Scale Heterogeneities in the Lithosphere do not Bias the Love-Rayleigh Discrepancy. Fulltekst i vitenarkiv
• Turquais, Pierre; Sollner, Walter; Asgedom, Endrias Getachew; Gelius, Leiv-J. & Maupin, Valerie (2018). Dictionary Learning and Sparse Representations for Denoising and Reconstruction of Marine Seismic Data. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Seismic signals are generally spread across many data samples of the recorded data. Applying a mathematical transformation to the data can however concentrate them on few samples only of the transform domain. Such representations are called sparse and have gained high interest in seismic processing because they build the necessary requirement to better compress or analyze the signal in the data. This thesis first assesses the effectiveness of building sparse representations for three critical seismic processing tasks, i.e., random noise attenuation, signal separation, and data reconstruction. The presented theory and the numerical experiments reveal that sparse representations can be used to achieve the aforementioned processing tasks under the condition that the signal has a high level of sparsity in the transform domain. It then follows an investigation of the transforms that can lead to sparse representations of the seismic data. A particular focus is placed on dictionary learning (DL) methods. These methods are applied to a data set to find a dictionary that can be used for sparse representation of the data set. The dictionary is a set of signals, called atoms, that represent elementary patterns of the data, and the sparse representation is found by reconstruction of the data with linear combinations of few dictionary atoms. The conventional DL methods are examined, and various modifications are implemented to develop three DL-based methods that are better adapted to each of the seismic processing tasks of interest. (1) A DL method is developed to attenuate the random noise in the seismic data. This method learns a dictionary and finds a sparse approximation of the data based on a statistical measure of the coherence in the residuals. Due to this particularity, the method is released from the need of the a priori knowledge of the noise energy. This is attractive for seismic data applications because the noise in seismic data has an intensity that is often unknown and that is varying across the data set. (2) A DL-based method is developed to separate the coherent noise from the seismic data. Some types of noise that contaminate seismic data cannot be removed with random noise attenuation methods because they appear with spatial or temporal coherency in the data. To tackle such noise, DL is combined with a statistical classification. First, DL is applied to the noise-contaminated data, which results in a dictionary of atoms representing either signal patterns or noise patterns. Using a statistical classification, the noise atoms are separated from the signal atoms, which divides the dictionary into a subdictionary of noise atoms and a subdictionary of signal atoms. Then, by finding a sparse representation of the data in the two subdictionary domains, the signal and the noise contributions in the data are identified and separated. This DL-based method has compelling advantages compared to the traditional coherent noise removal methods based on sparse representation; it does not require someone to search for adequate transforms that may sparsify the signal and the noise, and it adapts to the signal and noise in the data for an optimal separation. (3) a DL method is developed to interpolate and regularize the seismic data. In this method, each learned atom is constrained to represent an elementary waveform that has a constant amplitude along a parabolic traveltime moveout characterized by kinematic wavefield parameters. Such a parabolic structure is consistent with the physics of the seismic wavefield propagation and it can be used to easily interpolate and extrapolate the atoms. Using this advantage, the method can interpolate and regularize the seismic data. The process consists in learning a parabolic dictionary, interpolating the atoms, and computing a sparse representation of the data in the interpolated dictionary domain. Benefiting from the parabolic structure, the sparsity promotion, and the data adaptation, this method is able to interpolate severely aliased data. The three proposed DL methods are validated with synthetic and field seismic data examples. The effectiveness of the denoising methods are also assessed in comparison to industry-standard and state-of-the-art methods. Each method is demonstrated to be valuable for seismic processing.

• Gebregergs, Hagos G.; Gelius, Leiv-J. & Maupin, Valerie (2016). Compensation of Absorption Effects in Seismic Data. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  The frequency content of seismic data is changing with propagation depth due to intrinsic absorption. This implies that the higher frequencies are highly attenuated, thus leading to a loss in resolution of the seismic image. In addition, absorption anomalies, for example, caused by gas sands, will further dim the seismic reconstruction. The absorptive property of a medium can be described by a quality factor Q, which determines the energy decay and a velocity dispersion relationship. The quality factor and the velocity govern the propagation of seismic energy in the earth. It is possible to correct for such absorption effects by employing so-called inverse Q-filtering (IQF). This is a filtering technique that tries to restore the loss of the higher frequencies due to propagation. Newer developments within IQF can be regarded as a migration type of algorithm, and such classes of techniques are studied in this thesis.

Se alle arbeider i NVA