Ambient seismic noise correlations are widely used for high-resolution surface-wave imaging of Ea... more Ambient seismic noise correlations are widely used for high-resolution surface-wave imaging of Earth's lithosphere. Similar observations of the seismic body waves that propagate through the interior of Earth would provide a window into the deep Earth. We report the observation of the mantle transition zone through noise correlations of P waves as they are reflected by the discontinuities associated with the top [410 kliometers (km)] and the bottom (660 km) of this zone. Our data demonstrate that high-resolution mapping of the mantle transition zone is possible without using earthquake sources.
Journal of Geophysical Research: Solid Earth, 2004
Regional seismic tomography provides valuable information on the structure of shields, thereby ga... more Regional seismic tomography provides valuable information on the structure of shields, thereby gaining insight to the formation and stabilization of old continents. Fennoscandia (known as the Baltic Shield for its exposed part) is a composite shield for which the last recorded tectonic event is the intrusion of the Rapakivi granitoids around 1.6 Ga. A seismic experiment carried out as part of the European project Svecofennian-Karelia-Lapland-Kola (SVEKALAPKO) was designed to study the upper mantle of the Finnish part of the Baltic Shield, especially the boundary between Archean and Proterozoic domains. We invert the fundamental mode Rayleigh waves to obtain a three-dimensional shear wave velocity model using a ray-based method accounting for the curvature of wave fronts. The experiment geometry allows an evaluation of lateral variations in velocities down to 150 km depth. The obtained model exhibits variations of up to ±3% in S wave velocities. As the thermal variations beneath Finland are very small, these lateral variations must be caused by different rock compositions. The lithospheres beneath the Archean and Proterozoic domains are not noticeably different in the S wave velocity maps. A classification of the velocity profiles with depth yields four main families and five intermediate regions that can be correlated with surface features. The comparison of these profiles with composition-based shear wave velocities implies both lateral and vertical variations of the mineralogy.
In this paper, local seismic tomographic method is used to find the terrane distribution within t... more In this paper, local seismic tomographic method is used to find the terrane distribution within the central parts of the accretionary Svecofennian Orogen. This study presents a crustal Pwave velocity model, and for the first time the S-wave velocity and Vp/Vs ratio model of SVEKALAPKO area that is 700 × 800 km 2 in southern and central Finland. The 3-D model is presented as P-and S-wave velocity as well as Vp/Vs ratio depth slices and vertical sections. The data set comprised of several subsets of crustal Pg-and Sg-wave traveltime data: from local events recorded by the SVEKALAPKO seismic tomography array in 1998-1999, from older controlled source shots recorded at portable stations as well as at permanent stations, and from non-controlled chemical explosions recorded at permanent seismic stations. From 300 local explosions a total of 10 404 Pg-wave and 9361 Sg-wave arrival times were inverted to create independent 3-D Vp and Vs tomographic models, from which the Vp/Vs ratio was calculated. According to sensitivity tests, the optimal horizontal resolution of recognizable velocity structures in the central study area is at least 60 km down to depths of 40 km. In the final model, the seismic velocities vary smoothly. The lateral variations are larger for
Seismotectonic interpretations in regions characterized by low to moderate seismicity require con... more Seismotectonic interpretations in regions characterized by low to moderate seismicity require consistent earthquake catalogues covering periods of several decades. Inevitable changes in network configuration and analysing procedures, however, introduce significant bias to the hypocentre parameters and uncertainty estimates reported in such catalogues. To overcome these limitations, we developed a procedure using coupled hypocentre-velocity inversions to compute consistent hypocentre locations covering time periods of several decades while accounting for changes in network geometry. We apply these procedures to 35 yr of instrumentally recorded seismicity along the Rhône-Simplon fault system in southwest Switzerland, which is at the transition between the Central and Western Alps. The entire catalogue is relocated using a probabilistic location algorithm in combination with the derived minimum 1-D velocity models. A combination of location parameters is used to define consistent locationquality classes allowing for reliable interpretation of epicentres and focal depths. The relocated catalogue is interpreted together with a recent 3-D P-wave tomographic model and available 2-D reflection seismic profiles. The relocated hypocentres indicate that the major band of seismicity north of the Rhône valley is associated with a 30-40 km long, steeply north-dipping shear zone, which roots in the crystalline basement of the Aar Massif and extends to the shallowest levels of the sedimentary cover of the Helvetic nappes in the Rawil Depression. Seismicity towards the southwest indicates the existence of a similar shear zone within the Aiguille Rouge Massif. This zone possibly extends to the northeast and joins the Rawil fault zone. To the south of the Rhône valley, seismicity is scattered within the Penninic nappes, but limited to the hanging wall of the Pennine Basal Thrust (PBT). The Penninic nappes are characterized by a relatively higher V P of about 5 per cent compared to the Aar Massif, indicating differences in composition or metamorphic grade across the PBT.
This USER«S GUIDE to VELEST is intended to provide a brief introduction on how to run and use the... more This USER«S GUIDE to VELEST is intended to provide a brief introduction on how to run and use the program to simultaneously locate earthquakes and to calculate 1-D (layered) velocity models with station corrections. As an introduction to the coupled hypocenter-velocity model problem the reader is referred to Crosson (1976), Ellsworth (1977), and Thurber (1981). The concept of a 'Minimum 1-D model' is described in detail by Kissling (1988) and Kissling et al. (1995), who also provide several examples of applications of such 1-D velocity models for both improved earthquake locations and as initial reference models for 3-D seismic tomography. Kissling et al. (1994)-after describing the effects of initial reference models on 3-D tomographic results-in an appendix provide a brief overview over the procedure to be followed to calculate a 'Minimum 1-D model' with VELEST. The following USER'S GUIDE is written under the assumption that the reader is vaguely familiar with the problems and solutions described in the above mentioned publications (see reference list). Here only a brief overview will be given. Program VELEST (iteratively, i.e., "non-linearly") solves * in 'simultaneous mode': the coupled hypocenter-velocity model problem for local earthquakes, quarry blasts, and shots; for fixed velocity model and station corrections VELEST in simultaneous mode performs the Joint-Hypocenter-Determination (JHD). * in 'single-event-mode': the location problem for local earthquakes, blasts, and shots.
The POLENET/LAPNET broadband seismic array was deployed in northern Fennoscandia (Finland, Sweden... more The POLENET/LAPNET broadband seismic array was deployed in northern Fennoscandia (Finland, Sweden, Norway, and Russia) during the third International Polar Year 2007-2009. The array consisted of roughly 60 seismic stations. In our study we estimate the 3-D architecture of the upper mantle beneath the northern Fennoscandian shield using high-resolution teleseismic P-wave tomography. For this purpose 111 clearly recorded teleseismic events were selected and the data from the stations handpicked and analysed. Our study reveals a highly heterogeneous lithospheric mantle beneath the northern Fennoscandian shield though without any large high P-wave velocity area that may indicate presence of thick depleted lithospheric "keel". The most significant feature seen in the velocity model is a large elongated negative velocity anomaly (up to −3.5 %) in depth range 100-150 km in the central part of our study area that can be followed down to a depth of 200 km in some local areas. This lowvelocity area separates three high-velocity regions corresponding to the cratons and it extends to greater depth below the Karelian craton. 1 Introduction Recently, dense two-dimensional (2-D) arrays of broadband seismic instruments have proved to be a most effective mean to study the 3-D structure of the lithosphere and the lithosphere-asthenosphere boundary (LAB) (Trampert and Van der Hilst, 2005). One of such arrays was the POLENET/LAPNET broadband seismic array (http: //www.oulu.fi/sgo-oty/lapnet) deployed in northern Fennoscandia (Finland, Sweden, Norway, and Russia) during the third International Polar Year 2007-2009. The project was a part of POLENET (POLar Earth observing NETwork, http://www.polenet.org) consortium. The array consisted of 37 temporary and 21 permanent seismic stations (Fig. 1). All the stations, except of 2 temporary stations, were the broadband ones.
The first implemented AlpArray Complementary Experiment is called Eastern Alpine Seismic Investig... more The first implemented AlpArray Complementary Experiment is called Eastern Alpine Seismic Investigation (EASI). The Eastern, “straight“ part of the Alps is home to a number of open questions, e.g., the origin of the hanging lithospheric slab (Adriatic or European?), the nature of the Moho “hole” between the two plates, the anisotropic nature of the lower crust, and the relationship of the Alpine orogen to the adjacent foreland basin and the lithospheric blocks of the Bohemian Massif. Our research methods include tomography, ambient noise analysis and receiver functions, with anisotropy included in all three types of investigations as well as in shear-wave splitting analyses. The depth range of investigations encompasses the crust and the mantle lithosphere, down to the LAB.
The AlpArray Gravity Research Group (AAGRG), as part of the European AlpArray program, focuses on... more The AlpArray Gravity Research Group (AAGRG), as part of the European AlpArray program, focuses on the compilation of a homogeneous surface-based gravity data set across the Alpine area. In 2017 10 European countries in the Alpine realm agreed to contribute with gravity data for a new compilation of the Alpine gravity field in an area spanning from 2 to 23 • E and from 41 to 51 • N. This compilation relies on existing national gravity databases and, for the Ligurian and the Adriatic seas, on shipborne data of the Service Hydrographique et Océanographique de la Marine and of the Bureau Gravimétrique International. Furthermore,
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The role of mantle-lithosphere interactions in shaping mountain belts has long been debated. Seve... more The role of mantle-lithosphere interactions in shaping mountain belts has long been debated. Several conceptual models implicate a key role for horizontal kinematic forces in sustaining mountain building processes. For the central European Alps, however, recent stratigraphic, palaeo-altimetry and lithosphere structural evidence suggest that dynamic vertical forces — provided by a Slab Rollback Orogeny (SRO) model — are the primary determinant of the latest construction of thick nappe successions, the large-scale tectonic evolution, and the present-day seismicity pattern. In this study we investigate this hypothesis by performing 2-D, high-resolution, rheologically consistent, visco-elasto-plastic seismo-thermo-mechanical numerical modeling, which simulates both tectonic and seismic processes in a subduction and continental collision setting. Our numerical experiments reproduce the self-driven stages of oceanic subduction, continent-continent collision, and spontaneous slab breakoff....
Journal of Geophysical Research: Solid Earth, 2016
We investigate 3‐D local earthquake tomography for high‐quality travel time arrivals from aftersh... more We investigate 3‐D local earthquake tomography for high‐quality travel time arrivals from aftershocks following the 2010 M7.0 Haiti earthquake on the Léogâne fault. The data were recorded by 35 stations, including 19 ocean bottom seismometers, from which we selected 595 events to simultaneously invert for hypocenter location and 3‐D Vp and Vs velocity structures in southern Haiti. We performed several resolution tests and concluded that clear features can be recovered to a depth of 15 km. At 5 km depth we distinguish a broad low‐velocity zone in the Vp and Vs structure offshore near Gonave Island, which correlate with layers of marine sediments. Results show a pronounced low‐velocity zone in the upper 5 km across the city of Léogâne, which is consistent with the sedimentary basin location from geologic map. At 10 km depth, we detect a low‐velocity anomaly offshore near the Trois Baies fault and a NW‐SE directed low‐velocity zone onshore across Petit‐Goâve and Jacmel, which is consis...
AlpArray is a large collaborative seismological project in Europe that includes more than 50 rese... more AlpArray is a large collaborative seismological project in Europe that includes more than 50 research institutes and seismological observatories. At the heart of the project is the collection of top-quality seismological data from a dense network of broadband temporary seismic stations, in compliment to the existing permanent networks, that ensures a homogeneous station coverage of the greater Alpine region. This Alp Array Seismic Network (AASN) began operation in January 2016 and will have a duration of at least 2 years. In this work we report the Swiss contribution to the AASN, we concentrate on the site selection process, our methods for stations installation, data quality and data management. We deployed 27 temporary broadband stations equipped with STS-2 and Trillium Compact 120 s sensors. The deployment and maintenance of the temporary stations across 5 countries is managed by ETH Zurich and it is the result of a fruitful collaboration between five institutes in Europe.
Eos, Transactions American Geophysical Union, 1999
An international, interdisciplinary project, which 2 years ago deployed the largest dense seismic... more An international, interdisciplinary project, which 2 years ago deployed the largest dense seismic antenna ever in Europe, expects in the next 2 years to present important findings on the lithosphere and asthenosphere of a portion of the Trans‐European Suture Zone (TESZ). Final processing is currently under way of the data from the array of 120 seismographs along a 900‐km‐long by 100‐km‐wide strip from Gottingen, Germany, in the south, through Denmark, to Stockholm, Sweden in the north, across the northwestern part of the TESZ (Figure 1).Project Tor is a teleseismic tomography experiment with interdisciplinary data exploitation. It extends across the broad TESZ boundary between two markedly different lithospheric domains.These are (1) Proterozoic Europe, with Precambrian crust in Sweden and eastern Europe, and (2) Phanerozoic central Europe, with most of the crust influenced by the Caledonian and Variscan orogenies and only small areas of relic Precambrian crust. The project is desig...
Teleseismic tomography across the Chinese Tien Shan shows that seismic wave speeds in the lithosp... more Teleseismic tomography across the Chinese Tien Shan shows that seismic wave speeds in the lithosphere beneath central Tien Shan are high and therefore the lithosphere is not weaker than that beneath the adjacent undeformed Tarim and Junggar basins. There is evidence for significant velocity contrasts within the lithosphere that are presumably inherited from the Palaeozoic collision history. The high-velocity, thick Yili block observed underneath the northern Tien Shan is a clue for
Focal parameters of local earthquakes in the region of the Ionian Islands of western Greece are c... more Focal parameters of local earthquakes in the region of the Ionian Islands of western Greece are constrained with a temporary dense array of three-component seismographs operated jointly offshore and onshore. Seismic deformation is documented to be confined to the east of the N20"E-striking steep continental slope west of Cephalonia island, the right-lateral Cephalonia Transform Fault, CTF, inferred from large earthquakes. The pre-Apulian continental material appears to be only deforming east of the transform fault, where it is in upper plate position to the Hellenic subduction. East of the transform fault, the transmission velocity tomography from local earthquakes, compared in depth-section with a previous marine reflection profile, provides evidence in support of a shallow landward dipping boundary around 12 km deep under the Ionian Islands along which they may override the lower plate. On either side of this interface local earthquakes occur with different focal mechanisms, in support with its interpretation as the interplate. Under Cephalonia island, reverse-faulting deforms the upper plate along NW-SE structures, which may also be affected by left-lateral bookshelf-faulting. Small earthquakes show normal faulting along the western coast of Cephalonia and its extension 20 km SSW, the trace of the CTF as inferred from the occurrence of the large strikeslip earthquakes. Another group of normal-fault earthquakes locates in the lower plate from under Cephalonia to Zante, just outboard of a possible change of interplate dip suggested from reflection seismics landward under the islands. These normal-fault earthquakes appear to coincide in position with that of the load imposed by the upper plate transported over them, rather than occurring in an outer rise, outboard the plate boundary and trench, as observed in other subductions and attributed to the control by the flexural bending of the lower plate under the pull of the sinking slab. Interpretation has to consider several peculiar features of plate interaction in western Greece with respect to a steady-state model for major subduction zones, in particular: a fast deformation of the upper plate in front of an orogenically overthickened crust and of the southwestward push of extruding Anatolia; its transport, which is the cause of the migration of the plate boundary rather than the roll-back of a slab which has been proposed to be detached; possibly a flat and ramp shape of the interplate: the geometrical complexity of the shear limit across the CTF between subduction and collision, and the nearby variation of the nature of the foreland crust. O 2000 p.
During summer of 1995 local seismicity was recorded in the area around the Gulf of Arta in northw... more During summer of 1995 local seismicity was recorded in the area around the Gulf of Arta in northwestern Greece by a dense temporary seismic network. Of the 441 local events observed at 37 stations, 232 well locatable events with a total of 2776 P-phase readings were selected applying the criteria of a minimum of 6 P-observations and an azimuthal gap less than 180º. This data set is used to compute a minimum 1D velocity model for the region. Several tests are conducted to estimate model stability and hypocenter uncertainties, leading to the conclusion that relative hypocenter location accuracy is about 500 m in latitude and longitude and 1 km in depth. The minimum 1D velocity model serves as initial model in the non-linear inversion for three-dimensional P-velocity crustal structure by iteratively solving the coupled hypocenter-velocity problem in a least-squares sense. Careful analysis of the resolution capability of our data set outlines the well resolved features for interpretation. The resulting 3D velocity model shows generally higher average crustal velocities in the east, and the well resolved area of the eastern Gulf of Arta exhibits a homogeneous velocity around 6 km=s for the whole upper crust. A pronounced north-south trending zone of low velocities in the upper 5-10 km is observed in the area of the Katouna fault zone (KFZ). At greater depths (below 10 km) the KFZ is underlain by high-velocity material. E-W profiles suggest a horst-graben structure associated with the KFZ.
A complete Alpine cross section integrates numerous seismic reflection and refraction profiles, a... more A complete Alpine cross section integrates numerous seismic reflection and refraction profiles, across and along strike, with published and new field data. The deepest parts of the profile are constrained by geophysical data only, while structural features at intermediate levels are largely depicted according to the results of three‐dimensional models making use of seismic and field geological data. The geometry of the highest structural levels is constrained by classical along‐strike projections of field data parallel to the pronounced easterly axial dip of all tectonic units. Because the transect is placed close to the western erosional margin of the Austroalpine nappes of the Eastern Alps, it contains all the major tectonic units of the Alps. A model for the tectonic evolution along the transect is proposed in the form of scaled and area‐balanced profile sketches. Shortening within the Austroalpine nappes is testimony of a separate Cretaceous‐age orogenic event. West directed thr...
One-dimensional (1D) velocity models are still widely used for computing earthquake locations at ... more One-dimensional (1D) velocity models are still widely used for computing earthquake locations at seismological centers or in regions where three-dimensional (3D) velocity models are not available due to the lack of data of sufficiently high quality. The concept of the minimum 1D model with appropriate station corrections provides a framework to compute initial hypocenter locations and seismic velocities for local earthquake tomography. Since a minimum 1D model represents a solution to the coupled hypocenter-velocity problem it also represents a suitable velocity model for earthquake location and data quality assessment, such as evaluating the consistency in assigning pre-defined weighting classes and average picking error. Nevertheless, the use of a simple 1D velocity structure in combination with station delays raises the question of how appropriate the minimum 1D model concept is when applied to complex tectonic regions with significant three-dimensional (3D) variations in seismic velocities. In this study we compute one regional minimum 1D model and three local minimum 1D models for selected subregions of the Swiss Alpine region, which exhibits a strongly varying Moho topography. We compare the regional and local minimum 1D models in terms of earthquake locations and data quality assessment to measure their performance. Our results show that the local minimum 1D models provide more realistic hypocenter locations and better data fits than a single model for the Alpine region. We attribute this to the fact that in a local minimum 1D model local and regional effects of the velocity structure can be better separated. Consequently, in tectonically complex regions, minimum 1D models should be computed in sub-regions defined by similar structure, if they are used for earthquake location and data quality assessment.
Ambient seismic noise correlations are widely used for high-resolution surface-wave imaging of Ea... more Ambient seismic noise correlations are widely used for high-resolution surface-wave imaging of Earth's lithosphere. Similar observations of the seismic body waves that propagate through the interior of Earth would provide a window into the deep Earth. We report the observation of the mantle transition zone through noise correlations of P waves as they are reflected by the discontinuities associated with the top [410 kliometers (km)] and the bottom (660 km) of this zone. Our data demonstrate that high-resolution mapping of the mantle transition zone is possible without using earthquake sources.
Journal of Geophysical Research: Solid Earth, 2004
Regional seismic tomography provides valuable information on the structure of shields, thereby ga... more Regional seismic tomography provides valuable information on the structure of shields, thereby gaining insight to the formation and stabilization of old continents. Fennoscandia (known as the Baltic Shield for its exposed part) is a composite shield for which the last recorded tectonic event is the intrusion of the Rapakivi granitoids around 1.6 Ga. A seismic experiment carried out as part of the European project Svecofennian-Karelia-Lapland-Kola (SVEKALAPKO) was designed to study the upper mantle of the Finnish part of the Baltic Shield, especially the boundary between Archean and Proterozoic domains. We invert the fundamental mode Rayleigh waves to obtain a three-dimensional shear wave velocity model using a ray-based method accounting for the curvature of wave fronts. The experiment geometry allows an evaluation of lateral variations in velocities down to 150 km depth. The obtained model exhibits variations of up to ±3% in S wave velocities. As the thermal variations beneath Finland are very small, these lateral variations must be caused by different rock compositions. The lithospheres beneath the Archean and Proterozoic domains are not noticeably different in the S wave velocity maps. A classification of the velocity profiles with depth yields four main families and five intermediate regions that can be correlated with surface features. The comparison of these profiles with composition-based shear wave velocities implies both lateral and vertical variations of the mineralogy.
In this paper, local seismic tomographic method is used to find the terrane distribution within t... more In this paper, local seismic tomographic method is used to find the terrane distribution within the central parts of the accretionary Svecofennian Orogen. This study presents a crustal Pwave velocity model, and for the first time the S-wave velocity and Vp/Vs ratio model of SVEKALAPKO area that is 700 × 800 km 2 in southern and central Finland. The 3-D model is presented as P-and S-wave velocity as well as Vp/Vs ratio depth slices and vertical sections. The data set comprised of several subsets of crustal Pg-and Sg-wave traveltime data: from local events recorded by the SVEKALAPKO seismic tomography array in 1998-1999, from older controlled source shots recorded at portable stations as well as at permanent stations, and from non-controlled chemical explosions recorded at permanent seismic stations. From 300 local explosions a total of 10 404 Pg-wave and 9361 Sg-wave arrival times were inverted to create independent 3-D Vp and Vs tomographic models, from which the Vp/Vs ratio was calculated. According to sensitivity tests, the optimal horizontal resolution of recognizable velocity structures in the central study area is at least 60 km down to depths of 40 km. In the final model, the seismic velocities vary smoothly. The lateral variations are larger for
Seismotectonic interpretations in regions characterized by low to moderate seismicity require con... more Seismotectonic interpretations in regions characterized by low to moderate seismicity require consistent earthquake catalogues covering periods of several decades. Inevitable changes in network configuration and analysing procedures, however, introduce significant bias to the hypocentre parameters and uncertainty estimates reported in such catalogues. To overcome these limitations, we developed a procedure using coupled hypocentre-velocity inversions to compute consistent hypocentre locations covering time periods of several decades while accounting for changes in network geometry. We apply these procedures to 35 yr of instrumentally recorded seismicity along the Rhône-Simplon fault system in southwest Switzerland, which is at the transition between the Central and Western Alps. The entire catalogue is relocated using a probabilistic location algorithm in combination with the derived minimum 1-D velocity models. A combination of location parameters is used to define consistent locationquality classes allowing for reliable interpretation of epicentres and focal depths. The relocated catalogue is interpreted together with a recent 3-D P-wave tomographic model and available 2-D reflection seismic profiles. The relocated hypocentres indicate that the major band of seismicity north of the Rhône valley is associated with a 30-40 km long, steeply north-dipping shear zone, which roots in the crystalline basement of the Aar Massif and extends to the shallowest levels of the sedimentary cover of the Helvetic nappes in the Rawil Depression. Seismicity towards the southwest indicates the existence of a similar shear zone within the Aiguille Rouge Massif. This zone possibly extends to the northeast and joins the Rawil fault zone. To the south of the Rhône valley, seismicity is scattered within the Penninic nappes, but limited to the hanging wall of the Pennine Basal Thrust (PBT). The Penninic nappes are characterized by a relatively higher V P of about 5 per cent compared to the Aar Massif, indicating differences in composition or metamorphic grade across the PBT.
This USER«S GUIDE to VELEST is intended to provide a brief introduction on how to run and use the... more This USER«S GUIDE to VELEST is intended to provide a brief introduction on how to run and use the program to simultaneously locate earthquakes and to calculate 1-D (layered) velocity models with station corrections. As an introduction to the coupled hypocenter-velocity model problem the reader is referred to Crosson (1976), Ellsworth (1977), and Thurber (1981). The concept of a 'Minimum 1-D model' is described in detail by Kissling (1988) and Kissling et al. (1995), who also provide several examples of applications of such 1-D velocity models for both improved earthquake locations and as initial reference models for 3-D seismic tomography. Kissling et al. (1994)-after describing the effects of initial reference models on 3-D tomographic results-in an appendix provide a brief overview over the procedure to be followed to calculate a 'Minimum 1-D model' with VELEST. The following USER'S GUIDE is written under the assumption that the reader is vaguely familiar with the problems and solutions described in the above mentioned publications (see reference list). Here only a brief overview will be given. Program VELEST (iteratively, i.e., "non-linearly") solves * in 'simultaneous mode': the coupled hypocenter-velocity model problem for local earthquakes, quarry blasts, and shots; for fixed velocity model and station corrections VELEST in simultaneous mode performs the Joint-Hypocenter-Determination (JHD). * in 'single-event-mode': the location problem for local earthquakes, blasts, and shots.
The POLENET/LAPNET broadband seismic array was deployed in northern Fennoscandia (Finland, Sweden... more The POLENET/LAPNET broadband seismic array was deployed in northern Fennoscandia (Finland, Sweden, Norway, and Russia) during the third International Polar Year 2007-2009. The array consisted of roughly 60 seismic stations. In our study we estimate the 3-D architecture of the upper mantle beneath the northern Fennoscandian shield using high-resolution teleseismic P-wave tomography. For this purpose 111 clearly recorded teleseismic events were selected and the data from the stations handpicked and analysed. Our study reveals a highly heterogeneous lithospheric mantle beneath the northern Fennoscandian shield though without any large high P-wave velocity area that may indicate presence of thick depleted lithospheric "keel". The most significant feature seen in the velocity model is a large elongated negative velocity anomaly (up to −3.5 %) in depth range 100-150 km in the central part of our study area that can be followed down to a depth of 200 km in some local areas. This lowvelocity area separates three high-velocity regions corresponding to the cratons and it extends to greater depth below the Karelian craton. 1 Introduction Recently, dense two-dimensional (2-D) arrays of broadband seismic instruments have proved to be a most effective mean to study the 3-D structure of the lithosphere and the lithosphere-asthenosphere boundary (LAB) (Trampert and Van der Hilst, 2005). One of such arrays was the POLENET/LAPNET broadband seismic array (http: //www.oulu.fi/sgo-oty/lapnet) deployed in northern Fennoscandia (Finland, Sweden, Norway, and Russia) during the third International Polar Year 2007-2009. The project was a part of POLENET (POLar Earth observing NETwork, http://www.polenet.org) consortium. The array consisted of 37 temporary and 21 permanent seismic stations (Fig. 1). All the stations, except of 2 temporary stations, were the broadband ones.
The first implemented AlpArray Complementary Experiment is called Eastern Alpine Seismic Investig... more The first implemented AlpArray Complementary Experiment is called Eastern Alpine Seismic Investigation (EASI). The Eastern, “straight“ part of the Alps is home to a number of open questions, e.g., the origin of the hanging lithospheric slab (Adriatic or European?), the nature of the Moho “hole” between the two plates, the anisotropic nature of the lower crust, and the relationship of the Alpine orogen to the adjacent foreland basin and the lithospheric blocks of the Bohemian Massif. Our research methods include tomography, ambient noise analysis and receiver functions, with anisotropy included in all three types of investigations as well as in shear-wave splitting analyses. The depth range of investigations encompasses the crust and the mantle lithosphere, down to the LAB.
The AlpArray Gravity Research Group (AAGRG), as part of the European AlpArray program, focuses on... more The AlpArray Gravity Research Group (AAGRG), as part of the European AlpArray program, focuses on the compilation of a homogeneous surface-based gravity data set across the Alpine area. In 2017 10 European countries in the Alpine realm agreed to contribute with gravity data for a new compilation of the Alpine gravity field in an area spanning from 2 to 23 • E and from 41 to 51 • N. This compilation relies on existing national gravity databases and, for the Ligurian and the Adriatic seas, on shipborne data of the Service Hydrographique et Océanographique de la Marine and of the Bureau Gravimétrique International. Furthermore,
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The role of mantle-lithosphere interactions in shaping mountain belts has long been debated. Seve... more The role of mantle-lithosphere interactions in shaping mountain belts has long been debated. Several conceptual models implicate a key role for horizontal kinematic forces in sustaining mountain building processes. For the central European Alps, however, recent stratigraphic, palaeo-altimetry and lithosphere structural evidence suggest that dynamic vertical forces — provided by a Slab Rollback Orogeny (SRO) model — are the primary determinant of the latest construction of thick nappe successions, the large-scale tectonic evolution, and the present-day seismicity pattern. In this study we investigate this hypothesis by performing 2-D, high-resolution, rheologically consistent, visco-elasto-plastic seismo-thermo-mechanical numerical modeling, which simulates both tectonic and seismic processes in a subduction and continental collision setting. Our numerical experiments reproduce the self-driven stages of oceanic subduction, continent-continent collision, and spontaneous slab breakoff....
Journal of Geophysical Research: Solid Earth, 2016
We investigate 3‐D local earthquake tomography for high‐quality travel time arrivals from aftersh... more We investigate 3‐D local earthquake tomography for high‐quality travel time arrivals from aftershocks following the 2010 M7.0 Haiti earthquake on the Léogâne fault. The data were recorded by 35 stations, including 19 ocean bottom seismometers, from which we selected 595 events to simultaneously invert for hypocenter location and 3‐D Vp and Vs velocity structures in southern Haiti. We performed several resolution tests and concluded that clear features can be recovered to a depth of 15 km. At 5 km depth we distinguish a broad low‐velocity zone in the Vp and Vs structure offshore near Gonave Island, which correlate with layers of marine sediments. Results show a pronounced low‐velocity zone in the upper 5 km across the city of Léogâne, which is consistent with the sedimentary basin location from geologic map. At 10 km depth, we detect a low‐velocity anomaly offshore near the Trois Baies fault and a NW‐SE directed low‐velocity zone onshore across Petit‐Goâve and Jacmel, which is consis...
AlpArray is a large collaborative seismological project in Europe that includes more than 50 rese... more AlpArray is a large collaborative seismological project in Europe that includes more than 50 research institutes and seismological observatories. At the heart of the project is the collection of top-quality seismological data from a dense network of broadband temporary seismic stations, in compliment to the existing permanent networks, that ensures a homogeneous station coverage of the greater Alpine region. This Alp Array Seismic Network (AASN) began operation in January 2016 and will have a duration of at least 2 years. In this work we report the Swiss contribution to the AASN, we concentrate on the site selection process, our methods for stations installation, data quality and data management. We deployed 27 temporary broadband stations equipped with STS-2 and Trillium Compact 120 s sensors. The deployment and maintenance of the temporary stations across 5 countries is managed by ETH Zurich and it is the result of a fruitful collaboration between five institutes in Europe.
Eos, Transactions American Geophysical Union, 1999
An international, interdisciplinary project, which 2 years ago deployed the largest dense seismic... more An international, interdisciplinary project, which 2 years ago deployed the largest dense seismic antenna ever in Europe, expects in the next 2 years to present important findings on the lithosphere and asthenosphere of a portion of the Trans‐European Suture Zone (TESZ). Final processing is currently under way of the data from the array of 120 seismographs along a 900‐km‐long by 100‐km‐wide strip from Gottingen, Germany, in the south, through Denmark, to Stockholm, Sweden in the north, across the northwestern part of the TESZ (Figure 1).Project Tor is a teleseismic tomography experiment with interdisciplinary data exploitation. It extends across the broad TESZ boundary between two markedly different lithospheric domains.These are (1) Proterozoic Europe, with Precambrian crust in Sweden and eastern Europe, and (2) Phanerozoic central Europe, with most of the crust influenced by the Caledonian and Variscan orogenies and only small areas of relic Precambrian crust. The project is desig...
Teleseismic tomography across the Chinese Tien Shan shows that seismic wave speeds in the lithosp... more Teleseismic tomography across the Chinese Tien Shan shows that seismic wave speeds in the lithosphere beneath central Tien Shan are high and therefore the lithosphere is not weaker than that beneath the adjacent undeformed Tarim and Junggar basins. There is evidence for significant velocity contrasts within the lithosphere that are presumably inherited from the Palaeozoic collision history. The high-velocity, thick Yili block observed underneath the northern Tien Shan is a clue for
Focal parameters of local earthquakes in the region of the Ionian Islands of western Greece are c... more Focal parameters of local earthquakes in the region of the Ionian Islands of western Greece are constrained with a temporary dense array of three-component seismographs operated jointly offshore and onshore. Seismic deformation is documented to be confined to the east of the N20"E-striking steep continental slope west of Cephalonia island, the right-lateral Cephalonia Transform Fault, CTF, inferred from large earthquakes. The pre-Apulian continental material appears to be only deforming east of the transform fault, where it is in upper plate position to the Hellenic subduction. East of the transform fault, the transmission velocity tomography from local earthquakes, compared in depth-section with a previous marine reflection profile, provides evidence in support of a shallow landward dipping boundary around 12 km deep under the Ionian Islands along which they may override the lower plate. On either side of this interface local earthquakes occur with different focal mechanisms, in support with its interpretation as the interplate. Under Cephalonia island, reverse-faulting deforms the upper plate along NW-SE structures, which may also be affected by left-lateral bookshelf-faulting. Small earthquakes show normal faulting along the western coast of Cephalonia and its extension 20 km SSW, the trace of the CTF as inferred from the occurrence of the large strikeslip earthquakes. Another group of normal-fault earthquakes locates in the lower plate from under Cephalonia to Zante, just outboard of a possible change of interplate dip suggested from reflection seismics landward under the islands. These normal-fault earthquakes appear to coincide in position with that of the load imposed by the upper plate transported over them, rather than occurring in an outer rise, outboard the plate boundary and trench, as observed in other subductions and attributed to the control by the flexural bending of the lower plate under the pull of the sinking slab. Interpretation has to consider several peculiar features of plate interaction in western Greece with respect to a steady-state model for major subduction zones, in particular: a fast deformation of the upper plate in front of an orogenically overthickened crust and of the southwestward push of extruding Anatolia; its transport, which is the cause of the migration of the plate boundary rather than the roll-back of a slab which has been proposed to be detached; possibly a flat and ramp shape of the interplate: the geometrical complexity of the shear limit across the CTF between subduction and collision, and the nearby variation of the nature of the foreland crust. O 2000 p.
During summer of 1995 local seismicity was recorded in the area around the Gulf of Arta in northw... more During summer of 1995 local seismicity was recorded in the area around the Gulf of Arta in northwestern Greece by a dense temporary seismic network. Of the 441 local events observed at 37 stations, 232 well locatable events with a total of 2776 P-phase readings were selected applying the criteria of a minimum of 6 P-observations and an azimuthal gap less than 180º. This data set is used to compute a minimum 1D velocity model for the region. Several tests are conducted to estimate model stability and hypocenter uncertainties, leading to the conclusion that relative hypocenter location accuracy is about 500 m in latitude and longitude and 1 km in depth. The minimum 1D velocity model serves as initial model in the non-linear inversion for three-dimensional P-velocity crustal structure by iteratively solving the coupled hypocenter-velocity problem in a least-squares sense. Careful analysis of the resolution capability of our data set outlines the well resolved features for interpretation. The resulting 3D velocity model shows generally higher average crustal velocities in the east, and the well resolved area of the eastern Gulf of Arta exhibits a homogeneous velocity around 6 km=s for the whole upper crust. A pronounced north-south trending zone of low velocities in the upper 5-10 km is observed in the area of the Katouna fault zone (KFZ). At greater depths (below 10 km) the KFZ is underlain by high-velocity material. E-W profiles suggest a horst-graben structure associated with the KFZ.
A complete Alpine cross section integrates numerous seismic reflection and refraction profiles, a... more A complete Alpine cross section integrates numerous seismic reflection and refraction profiles, across and along strike, with published and new field data. The deepest parts of the profile are constrained by geophysical data only, while structural features at intermediate levels are largely depicted according to the results of three‐dimensional models making use of seismic and field geological data. The geometry of the highest structural levels is constrained by classical along‐strike projections of field data parallel to the pronounced easterly axial dip of all tectonic units. Because the transect is placed close to the western erosional margin of the Austroalpine nappes of the Eastern Alps, it contains all the major tectonic units of the Alps. A model for the tectonic evolution along the transect is proposed in the form of scaled and area‐balanced profile sketches. Shortening within the Austroalpine nappes is testimony of a separate Cretaceous‐age orogenic event. West directed thr...
One-dimensional (1D) velocity models are still widely used for computing earthquake locations at ... more One-dimensional (1D) velocity models are still widely used for computing earthquake locations at seismological centers or in regions where three-dimensional (3D) velocity models are not available due to the lack of data of sufficiently high quality. The concept of the minimum 1D model with appropriate station corrections provides a framework to compute initial hypocenter locations and seismic velocities for local earthquake tomography. Since a minimum 1D model represents a solution to the coupled hypocenter-velocity problem it also represents a suitable velocity model for earthquake location and data quality assessment, such as evaluating the consistency in assigning pre-defined weighting classes and average picking error. Nevertheless, the use of a simple 1D velocity structure in combination with station delays raises the question of how appropriate the minimum 1D model concept is when applied to complex tectonic regions with significant three-dimensional (3D) variations in seismic velocities. In this study we compute one regional minimum 1D model and three local minimum 1D models for selected subregions of the Swiss Alpine region, which exhibits a strongly varying Moho topography. We compare the regional and local minimum 1D models in terms of earthquake locations and data quality assessment to measure their performance. Our results show that the local minimum 1D models provide more realistic hypocenter locations and better data fits than a single model for the Alpine region. We attribute this to the fact that in a local minimum 1D model local and regional effects of the velocity structure can be better separated. Consequently, in tectonically complex regions, minimum 1D models should be computed in sub-regions defined by similar structure, if they are used for earthquake location and data quality assessment.
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Papers by Edi Kissling