High resolution reflection seismic profiling over the Tjellefonna fault in the Møre-Trøndelag Fault Complex, Norway

Abstract. The Møre-Trøndelag Fault Complex (MTFC) is one of the most prominent fault zones of Norway, both onshore and offshore. In spite of its importance, very little is known of the deeper structure of the individual fault segments comprising the fault complex. Most seismic lines have been recorded offshore or focused on deeper structures. This paper presents results from two reflection seismic profiles, located on each side of the Tingvollfjord, acquired over the Tjellefonna fault in the southeastern part of the MTFC. Possible kilometer scale vertical offsets, reflecting large scale northwest-dipping normal faulting, separating the high topography to the southeast from lower topography to the northwest have been proposed for the Tjellefonna fault or the Baeverdalen lineament. In this study, however, the Tjellefonna fault is interpreted to dip approximately 50–60° towards the southeast to depths of at least 1.3 km. Travel-time modeling of reflections associated with the fault was used to establish the geometry of the fault structure at depth, while detailed analysis of first P-wave arrivals in shot gathers, together with resistivity profiles, were used to define the near surface geometry of the fault zone. A continuation of the structure on the northeastern side of the Tingvollfjord is suggested by correlation of an in strike direction P-S converted reflection (generated by a fracture zone) seen on the reflection data from that side of the Tingvollfjord. The reflection seismic data correlate well with resistivity profiles and recently published near surface geophysical data. A highly reflective package forming a gentle antiform structure was also identified on both seismic profiles. This structure could be related to the folded amphibolite lenses seen on the surface or possibly by an important boundary within the gneissic basement rocks of the Western Gneiss Region. The fold hinge line of the structure is parallel with the Tjellefonna fault trace suggesting that the folding and faulting may have been related.

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High resolution reflection seismic profiling over the Tjellefonna fault in the Møre-Trøndelag Fault Complex, Norway

Solid Earth Discussions ◽

10.5194/sed-4-241-2012 ◽

2012 ◽

Vol 4 (1) ◽

pp. 241-278 ◽

Cited By ~ 1

Author(s):

E. Lundberg ◽

C. Juhlin ◽

A. Nasuti

Keyword(s):

P Wave ◽

The South ◽

Seismic Profiles ◽

Surface Geometry ◽

Secondary Fracture ◽

Near Surface ◽

North West ◽

Reflection Seismic ◽

North East ◽

The North

Abstract. The Møre-Trøndelag Fault Complex (MTFC) is one of the most prominent fault zones of Norway, both onshore and offshore. In spite of its importance, very little is known of the deeper structure of the individual fault segments comprising the fault complex. Most seismic lines have been recorded offshore or focused on deeper structures. This paper presents results from two reflection seismic profiles, located on each side of the Tingvollfjord, acquired over the Tjellefonna fault in the south-eastern part of the MTFC. Possible kilometer scale vertical offsets reflecting, large scale north-west dipping normal faulting separating the high topography to the south-east from lower topography to the north-west have been proposed for the Tjellefonna fault. In this study, however, the Tjellefonna fault is interpreted to dip approximately 50–60° towards the south-east to depths of at least 1.4 km. Travel-time modeling of reflections associated with the fault was used to establish the geometry of the fault structure at depth and detailed analysis of first P-wave arrivals in shot-gathers together with resistivity profiles were used to define the near surface geometry of the fault zone. A continuation of the structure on the north-eastern side of the Tingvollfjord is suggested by correlation of an in strike direction P-S converted reflection (generated by a fracture zone) seen on the reflection data from that side of the Tingvollfjord. The reflection seismic data correlate well with resistivity profiles and recently published near surface geophysical data. A highly reflective package forming a gentle antiform structure was also identified on both seismic profiles. The structure may be an important boundary within the gneissic basement rocks of the Western Gneiss Region. The Fold Hinge Line is parallel with the Tjellefonna fault trace while the topographic lineament diverges, following secondary fracture zones towards north-east.

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Subsurface characterization of a quick-clay vulnerable area using near-surface geophysics and hydrological modelling

Solid Earth ◽

10.5194/se-10-1685-2019 ◽

2019 ◽

Vol 10 (5) ◽

pp. 1685-1705

Author(s):

Silvia Salas-Romero ◽

Alireza Malehmir ◽

Ian Snowball ◽

Benoît Dessirier

Keyword(s):

Large Scale ◽

Geophysical Methods ◽

Hydrological Modelling ◽

P Wave ◽

Coarse Grained ◽

Near Surface ◽

Reflection Seismic ◽

Geotechnical Investigations ◽

Quick Clay ◽

Near Surface Geophysics

Abstract. Quick-clay landslides are common geohazards in Nordic countries and Canada. The presence of potential quick clays is confirmed using geotechnical investigations, but near-surface geophysical methods, such as seismic and resistivity surveys, can also help identify coarse-grained materials associated with the development of quick clays. We present the results of reflection seismic investigations on land and in part of the Göta River in Sweden, along which many quick-clay landslide scars exist. This is the first time that such a large-scale reflection seismic investigation has been carried out to study the subsurface structures associated with quick-clay landslides. The results also show a reasonable correlation with radio magnetotelluric and travel-time tomography models of the subsurface. Other ground geophysical data, such as high magnetic values, suggest a positive correlation with an increased thickness of the coarse-grained layer and shallower depths to the top of the bedrock and the top of the coarse-grained layer. The morphology of the river bottom and riverbanks, e.g. subaquatic landslide deposits, is shown by side-scan sonar and bathymetric data. Undulating bedrock, covered by subhorizontal sedimentary glacial and postglacial deposits, is clearly revealed. An extensive coarse-grained layer (P-wave velocity mostly between 1500 and 2500 m s−1 and resistivity from approximately 80 to 100 Ωm) exists within the sediments and is interpreted and modelled in a regional context. Several fracture zones are identified within the bedrock. Hydrological modelling of the coarse-grained layer confirms its potential for transporting fresh water infiltrated in fractures and nearby outcrops located in the central part of the study area. The modelled groundwater flow in this layer promotes the leaching of marine salts from the overlying clays by seasonal inflow–outflow cycles and/or diffusion, which contributes to the formation of potential quick clays.

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Two-dimensional elastic pseudo-spectral modeling of wide-aperture seismic array data with application to the Wichita Uplift-Anadarko Basin region of southwestern Oklahoma

Bulletin of the Seismological Society of America ◽

10.1785/bssa08006a1677 ◽

1990 ◽

Vol 80 (6A) ◽

pp. 1677-1695 ◽

Cited By ~ 2

Author(s):

Ik Bum Kang ◽

George A. McMechan

Keyword(s):

Large Scale ◽

Deep Structure ◽

Sedimentary Basins ◽

P Wave ◽

Two Dimensional ◽

Anadarko Basin ◽

Near Surface ◽

University Of Texas ◽

Wide Aperture ◽

The University

Abstract Full wave field modeling of wide-aperture data is performed with a pseudospectral implementation of the elastic wave equation. This approach naturally produces three-component stress and two-component particle displacement, velocity, and acceleration seismograms for compressional, shear, and Rayleigh waves. It also has distinct advantages in terms of computational requirements over finite-differencing when data from large-scale structures are to be modeled at high frequencies. The algorithm is applied to iterative two-dimensional modeling of seismograms from a survey performed in 1985 by The University of Texas at El Paso and The University of Texas at Dallas across the Anadarko basin and the Wichita Mountains in southwestern Oklahoma. The results provide an independent look at details of near-surface structure and reflector configurations. Near-surface (<3 km deep) structure and scattering effects account for a large percentage (>70 per cent) of the energy in the observed seismograms. The interpretation of the data is consistent with the results of previous studies of these data, but provides considerably more detail. Overall, the P-wave velocities in the Wichita Uplift are more typical of the middle crust than the upper crust (5.3 to 7.1 km/sec). At the surface, the uplift is either exposed as weathered outcrop (5.0 to 5.3 km/sec) or is overlain with sediments of up to 0.4 km in thickness, ranging in velocity from 2.7 to 3.4 km/sec, generally increasing with depth. The core of the uplift is relatively seismically transparent. A very clear, coherent reflection is observed from the Mountain View fault, which dips at ≈40° to the southwest, to at least 12 km depth. Velocities in the Anadarko Basin are typical of sedimentary basins; there is a general increase from ≈2.7 km/sec at the surface to ≈5.9 km/sec at ≈16 km depth, with discontinuous reflections at depths of ≈8, 10, 12, and 16 km.

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Geophysical imaging of permafrost in the SW Svalbard – the result of two high arctic expeditions to Spitsbergen

10.5194/egusphere-egu2020-8136 ◽

2020 ◽

Author(s):

Mariusz Majdanski ◽

Artur Marciniak ◽

Bartosz Owoc ◽

Wojciech Dobiński ◽

Tomasz Wawrzyniak ◽

...

Keyword(s):

Surface Waves ◽

Active Layer ◽

High Arctic ◽

The Arctic ◽

Seismic Profiles ◽

Frozen Ground ◽

Near Surface ◽

Seismic Processing ◽

Reflection Seismic ◽

Sea Coast

The Arctic regions are the place of the fastest observed climate change. One of the indicators of such evolution are changes occurring in the glaciers and the subsurface in the permafrost. The active layer of the permafrost as the shallowest one is well measured by multiple geophysical techniques and in-situ measurements.Two high arctic expeditions have been organized to use seismic methods to recognize the shape of the permafrost in two seasons: with the unfrozen ground (October 2017) and frozen ground (April 2018). Two seismic profiles have been designed to visualize the shape of permafrost between the sea coast and the slope of the mountain, and at the front of a retreating glacier. For measurements, a stand-alone seismic stations has been used with accelerated weight drop with in-house modifications and timing system. Seismic profiles were acquired in a time-lapse manner and were supported with GPR and ERT measurements, and continuous temperature monitoring in shallow boreholes.Joint interpretation of seismic and auxiliary data using Multichannel analysis of surface waves, First arrival travel-time tomography and Reflection imaging show clear seasonal changes affecting the active layer where P-wave velocities are changing from 3500 to 5200 m/s. This confirms the laboratory measurements showing doubling the seismic velocity of water-filled high-porosity rocks when frozen. The same laboratory study shows significant (>10%) increase of velocity in frozen low porosity rocks, that should be easily visible in seismic.In the reflection seismic processing, the most critical part was a detailed front mute to eliminate refracted arrivals spoiling wide-angle near-surface reflections. Those long offset refractions were however used to estimate near-surface velocities further used in reflection processing. In the reflection seismic image, a horizontal reflection was traced at the depth of 120 m at the sea coast deepening to the depth of 300 m near the mountain.Additionally, an optimal set of seismic parameters has been established, clearly showing a significantly higher signal to noise ratio in case of frozen ground conditions even with the snow cover. Moreover, logistics in the frozen conditions are much easier and a lack of surface waves recorded in the snow buried geophones makes the seismic processing simpler.Acknowledgements&#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160;This research was funded by the National Science Centre, Poland (NCN) Grant UMO-2015/21/B/ST10/02509.

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Finite-difference modelling to evaluate seismic P-wave and shear-wave field data

Solid Earth ◽

10.5194/se-6-33-2015 ◽

2015 ◽

Vol 6 (1) ◽

pp. 33-47 ◽

Cited By ~ 3

Author(s):

T. Burschil ◽

T. Beilecke ◽

C. M. Krawczyk

Keyword(s):

Wave Field ◽

Shear Wave ◽

Field Data ◽

P Wave ◽

Sh Wave ◽

Surface Shear ◽

Near Surface ◽

Reflection Seismic ◽

Surface Shear Wave ◽

Seismic Measurements

Abstract. High-resolution reflection seismic methods are an established non-destructive tool for engineering tasks. In the near surface, shear-wave reflection seismic measurements usually offer a higher spatial resolution in the same effective signal frequency spectrum than P-wave data, but data quality varies more strongly. To discuss the causes of these differences, we investigated a P-wave and a SH-wave seismic reflection profile measured at the same location on the island of Föhr, Germany and applied seismic reflection processing to the field data as well as finite-difference modelling of the seismic wave field. The simulations calculated were adapted to the acquisition field geometry, comprising 2 m receiver distance (1 m for SH wave) and 4 m shot distance along the 1.5 km long P-wave and 800 m long SH-wave profiles. A Ricker wavelet and the use of absorbing frames were first-order model parameters. The petrophysical parameters to populate the structural models down to 400 m depth were taken from borehole data, VSP (vertical seismic profile) measurements and cross-plot relations. The simulation of the P-wave wave-field was based on interpretation of the P-wave depth section that included a priori information from boreholes and airborne electromagnetics. Velocities for 14 layers in the model were derived from the analysis of five nearby VSPs (vP =1600–2300 m s-1). Synthetic shot data were compared with the field data and seismic sections were created. Major features like direct wave and reflections are imaged. We reproduce the mayor reflectors in the depth section of the field data, e.g. a prominent till layer and several deep reflectors. The SH-wave model was adapted accordingly but only led to minor correlation with the field data and produced a higher signal-to-noise ratio. Therefore, we suggest to consider for future simulations additional features like intrinsic damping, thin layering, or a near-surface weathering layer. These may lead to a better understanding of key parameters determining the data quality of near-surface shear-wave seismic measurements.

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3D seismic traveltime tomography imaging of the shallow subsurface at the C O2 SINK project site, Ketzin, Germany

Geophysics ◽

10.1190/1.3026553 ◽

2009 ◽

Vol 74 (1) ◽

pp. G1-G15 ◽

Cited By ~ 35

Author(s):

Sawasdee Yordkayhun ◽

Ari Tryggvason ◽

Ben Norden ◽

Christopher Juhlin ◽

Björn Bergman

Keyword(s):

Velocity Structure ◽

Velocity Model ◽

Geological Structure ◽

Seismic Survey ◽

Storage Site ◽

Near Surface ◽

Shallow Subsurface ◽

Traveltime Tomography ◽

Reflection Seismic ◽

Reflection Data

A 3D reflection seismic survey was performed in 2005 at the Ketzin carbon dioxide [Formula: see text] pilot geological-storage site (the [Formula: see text] project) near Berlin, Germany, to image the geological structure of the site to depths of about [Formula: see text]. Because of the acquisition geometry, frequency limitations of the source, and artefacts of the data processing, detailed structures shallower than about [Formula: see text] were unclear. To obtain structural images of the shallow subsurface, we applied 3D traveltime tomography to data near the top of the Ketzin anticline, where faulting is present. Understanding the shallow subsurface structure is important for long-term monitoring aspects of the project after [Formula: see text] has been injected into a saline aquifer at about [Formula: see text] depth. We used a 3D traveltime tomography algorithm based on a combination ofsolving for 3D velocity structure and static corrections in the inversion process to account for artefacts in the velocity structure because of smearing effects from the unconsolidated cover. The resulting velocity model shows low velocities of [Formula: see text] in the uppermost shallow subsurface of the study area. The velocity reaches about [Formula: see text] at a depth of [Formula: see text]. This coincides approximately with the boundary between Quaternary units, which contain the near-surface freshwater reservoir and the Tertiary clay aquitard. Correlation of tomographic images with a similarity attribute slice at [Formula: see text] (about [Formula: see text] depth) indicates that at least one east-west striking fault zone observed in the reflection data might extend into the Tertiary unit. The more detailed images of the shallow subsurface from this study provided valuable information on this potentially risky area.

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Seismic tomography studies of cover thickness and near-surface bedrock velocities

Geophysics ◽

10.1190/1.2345191 ◽

2006 ◽

Vol 71 (6) ◽

pp. U77-U84 ◽

Cited By ~ 20

Author(s):

B. Bergman ◽

A. Tryggvason ◽

C. Juhlin

Keyword(s):

Nuclear Waste ◽

Velocity Structure ◽

Synthetic Data ◽

General Situation ◽

Seismic Profiles ◽

Low Velocity ◽

Near Surface ◽

Reflection Seismic ◽

Crystalline Bedrock ◽

Cover Thickness

Reflection seismic imaging of the uppermost kilometer of crystalline bedrock is an important component in site surveys for locating potential storage sites for nuclear waste in Sweden. To obtain high-quality images, refraction statics are calculated using first-break traveltimes. These first-break picks may also be used to produce tomographic velocity images of the uppermost bedrock. In an earlier study, we presented a method applicable to data sets where the vast majority of shots are located in the bedrock below the glacial deposits, or cover, typical for northern latitudes. A by-product of this method was an estimate of the cover thickness from the receiver static that was introduced to sharpen the image. We now present a modified version of this method that is applicable for sources located in or on the cover, the general situation for nuclear waste site surveys. This modified methodalso solves for 3D velocity structure and static correctionssimultaneously in the inversion process. The static corrections can then be used to estimate the cover thickness. First, we test our tomography method on synthetic data withthe shot points in the bedrock below the cover. Next, we developa strategy for the case when the sources are within the cover. Themethod is then applied to field data from five crooked-line,high-resolution reflection seismic profiles ranging in lengthfrom 2 to [Formula: see text]. The crooked-line profiles make the study 2.5dimensional regarding bedrock velocities. The cover thicknessalong the profiles varies from 0 to [Formula: see text]. Estimated thickness ofthe cover agrees well with data from boreholes drilled near theprofiles. Low-velocity zones in the uppermost bedrock generallycorrelate with locations where reflections from the stackedsections project to the surface. Thus, the method is functional,both for imaging the uppermost bedrock velocities as well as for estimating the cover thickness.

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Subsurface structures of a quick-clay sliding prone area revealed using land-river reflection seismic data and hydrogeological modelling

10.5194/se-2019-22 ◽

2019 ◽

Author(s):

Silvia Salas-Romero ◽

Alireza Malehmir ◽

Ian Snowball ◽

Benoît Dessirier

Keyword(s):

Large Scale ◽

Geophysical Methods ◽

Coarse Grained ◽

Magnetic Data ◽

Near Surface ◽

Side Scan Sonar ◽

Reflection Seismic ◽

Subsurface Structures ◽

Geotechnical Investigations ◽

Quick Clay

Abstract. Quick-clay landslides are common geohazards in Nordic countries and Canada. The presence of potential quick clays is confirmed using geotechnical investigations, but near-surface geophysical methods, such as seismic and resistivity surveys, can also help identifying coarse-grained materials associated to the development of quick clays. We present the results of reflection seismic investigations on land and in part of the Göta River in Sweden, along which many quick-clay landslide scars exist. This is the first time that such a large-scale reflection seismic investigation has been carried out to study the subsurface structures associated with quick-clay landslides. The results also show a reasonable correlation with the radio magnetotelluric and traveltime tomography models. The morphology of the river bottom and riverbanks, as e.g. subaquatic landslide deposits, is shown by side-scan sonar and bathymetric data. Undulating bedrock, covered by subhorizontal sedimentary glacial and postglacial deposits is clearly revealed. An extensive coarse-grained layer exists in the sedimentary sequence and is interpreted and modelled in a regional context. Individual fractures and fracture zones are identified within bedrock and sediments. Hydrological modelling of the coarse-grained layer confirms its potential for transporting fresh water infiltrated in fractures and nearby outcrops. The groundwater flow in the coarse-grained layer promotes leaching of marine salts from the overlying clays by slow infiltration and/or diffusion, which helps in the formation of potential quick clays. Magnetic data show coarse-grained materials at the landslide scar located in the study area, which may have acted as a sliding surface together with quick clays.

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Structural analysis of S-wave seismics around an urban sinkhole: evidence of enhanced dissolution in a strike-slip fault zone

Natural Hazards and Earth System Science ◽

10.5194/nhess-17-2335-2017 ◽

2017 ◽

Vol 17 (12) ◽

pp. 2335-2350 ◽

Cited By ~ 7

Author(s):

Sonja H. Wadas ◽

David C. Tanner ◽

Ulrich Polom ◽

Charlotte M. Krawczyk

Keyword(s):

Fault Zone ◽

Fracture Network ◽

Strike Slip ◽

Strike Slip Fault ◽

Normal Faults ◽

S Wave ◽

Seismic Profiles ◽

Near Surface ◽

Reflection Seismic ◽

Enhanced Dissolution

Abstract. In November 2010, a large sinkhole opened up in the urban area of Schmalkalden, Germany. To determine the key factors which benefited the development of this collapse structure and therefore the dissolution, we carried out several shear-wave reflection-seismic profiles around the sinkhole. In the seismic sections we see evidence of the Mesozoic tectonic movement in the form of a NW–SE striking, dextral strike-slip fault, known as the Heßleser Fault, which faulted and fractured the subsurface below the town. The strike-slip faulting created a zone of small blocks ( < 100 m in size), around which steep-dipping normal faults, reverse faults and a dense fracture network serve as fluid pathways for the artesian-confined groundwater. The faults also acted as barriers for horizontal groundwater flow perpendicular to the fault planes. Instead groundwater flows along the faults which serve as conduits and forms cavities in the Permian deposits below ca. 60 m depth. Mass movements and the resulting cavities lead to the formation of sinkholes and dissolution-induced depressions. Since the processes are still ongoing, the occurrence of a new sinkhole cannot be ruled out. This case study demonstrates how S-wave seismics can characterize a sinkhole and, together with geological information, can be used to study the processes that result in sinkhole formation, such as a near-surface fault zone located in soluble rocks. The more complex the fault geometry and interaction between faults, the more prone an area is to sinkhole occurrence.

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Integrating high‐resolution refraction data into near‐surface seismic reflection data processing and interpretation

Geophysics ◽

10.1190/1.1444435 ◽

1998 ◽

Vol 63 (4) ◽

pp. 1339-1347 ◽

Cited By ~ 17

Author(s):

Kate C. Miller ◽

Steven H. Harder ◽

Donald C. Adams ◽

Terry O’Donnell

Keyword(s):

Seismic Reflection ◽

Velocity Model ◽

Surface Velocity ◽

Seismic Profiles ◽

Seismic Reflection Data ◽

Near Surface ◽

Interval Velocity ◽

Velocity Models ◽

Reflection Data ◽

Seismic Reflection Profiles

Shallow seismic reflection surveys commonly suffer from poor data quality in the upper 100 to 150 ms of the stacked seismic record because of shot‐associated noise, surface waves, and direct arrivals that obscure the reflected energy. Nevertheless, insight into lateral changes in shallow structure and stratigraphy can still be obtained from these data by using first‐arrival picks in a refraction analysis to derive a near‐surface velocity model. We have used turning‐ray tomography to model near‐surface velocities from seismic reflection profiles recorded in the Hueco Bolson of West Texas and southern New Mexico. The results of this analysis are interval‐velocity models for the upper 150 to 300 m of the seismic profiles which delineate geologic features that were not interpretable from the stacked records alone. In addition, the interval‐velocity models lead to improved time‐to‐depth conversion; when converted to stacking velocities, they may provide a better estimate of stacking velocities at early traveltimes than other methods.

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