TY  - JOUR
A1  - Ramos, Catalina
A1  - Mechie, James
A1  - Stiller, Manfred
T1  - Reflection seismic images and amplitude ratio modelling of the Chilean subduction zone at 38.25 degrees S
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - Active source near-vertical reflection (NVR) data from the interdisciplinary project TIPTEQ were used to image and identify structural and petrophysical properties within the Chilean subduction zone at 38.25 degrees S, where in 1960 the largest earthquake ever recorded (M-w 9.5) occurred. Reflection seismic images of the subduction zone were obtained using the post-stack depth migration technique to process the three components of the NVR data, allowing to present P- and S-stacked time sections and depth-migrated seismic reflection images. Next, the reflectivity method allowed to model traveltimes and amplitude ratios of pairs of reflections for two 1D profiles along the studied transect. The 1D seismic velocities that produced the synthetic seismograms with amplitudes and traveltimes that fit the observed ones were used to infer the rock composition of the different layers in each 1D profile. Finally, an image of the subduction zone is given. The Chilean subduction zone at 38.25 degrees S underlies a continental crust with highly reflective horizontal, as well as dipping events. Among them, the Lanalhue Fault Zone (LFZ), interpreted to be east-dipping, is imaged to very shallow depths for the first time. In terms of seismic velocities, the inferred composition of the continental crust is in agreement with field geology observations at the surface along the profile. Furthermore, no measurable amounts of fluids above the plate interface in the continental crust in this part of the Chilean subduction zone are necessary to explain the results. A large-scale anisotropy in the continental crust and upper mantle is qualitatively proposed. However, quantitative studies on this topic in the continental crust of the Chilean subduction zone at 38.25 degrees S do not exist to date.
KW  - Reflection seismics
KW  - Reflectivity method
KW  - Subduction zone
KW  - South America
Y1  - 2018
U6  - https://doi.org/10.1016/j.tecto.2018.10.007
SN  - 0040-1951
SN  - 1879-3266
VL  - 747
SP  - 115
EP  - 127
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Mechie, James
A1  - Abu-Ayyash, Khalil
A1  - Ben-Avraham, Zvi
A1  - El-Kelani, R.
A1  - Mohsen, Amjad
A1  - Rumpker, Georg
A1  - Saul, J.
A1  - Weber, Michael H.
T1  - Crustal shear velocity structure across the Dead Sea Transform from two-dimensional modelling of DESERT project explosion seismic data
N2  - An analysis of the shear (S) waves recorded during the wide-angle reflection/refraction (WRR) experiment as part of the DESERT project crossing the Dead Sea Transform (DST) reveals average crustal S-wave velocities of 3.3-3.5 km s(-1) beneath the WRR profile. Together with average crustal P-wave velocities of 5.8-6.1 km s(-1) from an already published study this provides average crustal Poisson's ratios of 0.26-0.27 (V-p/V-s = 1.76-1.78) below the profile. The top two layers consisting predominantly of sedimentary rocks have S- wave velocities of 1.8-2.7kms(-1) and Poisson's ratios of 0.25-0.31 (V-p/V-s = 1.73-1.91). Beneath these two layers the seismic basement has average S- wave velocities of around 3.6 km s(-1) east of the DST and about 3.7 km s(-1) west of the DST and Poisson's ratios of 0.24-0.25 (V-p/V-s = 1.71-1.73). The lower crust has an average S-wave velocity of about 3.75 km s(-1) and an average Poisson's ratio of around 0.27 (V-p/V-s = 1.78). No Sn phase refracted through the uppermost mantle was observed. The results provide for the first time information from controlled source data on the crustal S-wave velocity structure for the region west of the DST in Israel and Palestine and agree with earlier results for the region east of the DST in the Jordanian highlands. A shear wave splitting study using SKS waves has found evidence for crustal anisotropy beneath the WRR profile while a receiver function study has found evidence for a lower crustal, high S-wave velocity layer east of the DST below the profile. Although no evidence was found in the S-wave data for either feature, the S-wave data are not incompatible with crustal anisotropy being present as the WRR profile only lies 30 degrees off the proposed symmetry axis of the anisotropy where the difference in the two S-wave velocities is still very small. In the case of the lower crustal, high S-wave velocity layer, if the velocity change at the top of this layer comprises a small first-order discontinuity underlain by a 2 km thick transition zone, instead of just a large first-order discontinuity, then both the receiver function data and the WRR data presented here can be satisfied. Finally, the S-wave velocities and Poisson's ratios which have been derived in this study are typical of continental crust and do not require extensional processes to explain them
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Feld, Christian
A1  - Mechie, James
A1  - Hübscher, Christian
A1  - Hall, Jeremy
A1  - Nicolaides, Stelios
A1  - Gurbuz, Cemil
A1  - Bauer, Klaus
A1  - Louden, Keith
A1  - Weber, Michael
T1  - Crustal structure of the eratosthenes seamount, cyprus and S. Turkey from an amphibian wide-angle seismic profile
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - In 2010, project CoCoCo (incipient COntinent-COntinent COllision) recorded a 650 km long amphibian N-S wide-angle seismic profile, extending from the Anatolian plateau across southern Turkey and Cyprus to just south of the Eratosthenes Seamount (ESM). The aim of the project is to reveal the impact of the transition from subduction to continent-continent collision of Africa with Anatolia. Arrival picking, finite-differences ray-tracing and inversion of the offshore and on-offshore data produced a tomographic model across southern Cyprus, the accretionary wedge and the ESM. The main features of this model are (1) crustal P-velocities predominantly lower than 6.5 km/s beneath the ESM, (2) crustal thickness between 28 and 37 km, (3) an upper crustal reflection at 5 km depth beneath the ESM, (4) the likely presence of oceanic crust south of the ESM and a transform margin north of it and (5) a 12 km thick ophiolite sequence on Cyprus. Land shots on Turkey, also recorded on Cyprus, gravity data and geological and previous seismic investigations allow to derive a layered velocity model beneath Anatolia and the northern part of Cyprus. The main features of this model are (1) Moho depths of 38–45 km beneath the Anatolian plateau, (2) an upper and lower crust with large lateral changes in velocity and thickness, (3) a north-dipping subducting plate below Cyprus with a steepening of the dip-angle of the plate at about 45 km depth. Thus, the wide-angle seismic and gravity data provide detailed insights into the 2-D geometry and velocity structures associated with the Cyprus Arc collision zone. Finally, integrated analysis of the geophysics and geology allows a comprehensive interpretation of the crustal structure related to the collision process.
KW  - Controlled source seismology
KW  - Subduction zone processes
KW  - Continental margins: convergent
KW  - Crustal structure
KW  - Europe
KW  - Gravity anomalies and Earth structure
Y1  - 2017
U6  - https://doi.org/10.1016/j.tecto.2017.02.003
SN  - 0040-1951
SN  - 1879-3266
VL  - 700
SP  - 32
EP  - 59
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Mechie, James
A1  - Abu-Ayyash, Khalil
A1  - Ben-Avraham, Zvi
A1  - El-Kelani, Radwan
A1  - Qabbani, Isam
A1  - Weber, Michael H.
T1  - Crustal structure of the southern Dead Sea basin derived from project DESIRE wide-angle seismic data
N2  - As part of the DEad Sea Integrated REsearch project (DESIRE) a 235 km long seismic wide-angle reflection/ refraction (WRR) profile was completed in spring 2006 across the Dead Sea Transform (DST) in the region of the southern Dead Sea basin (DSB). The DST with a total of about 107 km multi-stage left-lateral shear since about 18 Ma ago, accommodates the movement between the Arabian and African plates. It connects the spreading centre in the Red Sea with the Taurus collision zone in Turkey over a length of about 1 100 km. With a sedimentary infill of about 10 km in places, the southern DSB is the largest pull-apart basin along the DST and one of the largest pull-apart basins on Earth. The WRR measurements comprised 11 shots recorded by 200 three-component and 400 one-component instruments spaced 300 m to 1.2 km apart along the whole length of the E-W trending profile. Models of the P-wave velocity structure derived from the WRR data show that the sedimentary infill associated with the formation of the southern DSB is about 8.5 km thick beneath the profile. With around an additional 2 km of older sediments, the depth to the seismic basement beneath the southern DSB is about 11 km below sea level beneath the profile. Seismic refraction data from an earlier experiment suggest that the seismic basement continues to deepen to a maximum depth of about 14 km, about 10 km south of the DESIRE profile. In contrast, the interfaces below about 20 km depth, including the top of the lower crust and the Moho, probably show less than 3 km variation in depth beneath the profile as it crosses the southern DSB. Thus the Dead Sea pull-apart basin may be essentially an upper crustal feature with upper crustal extension associated with the left- lateral motion along the DST. The boundary between the upper and lower crust at about 20 km depth might act as a decoupling zone. Below this boundary the two plates move past each other in what is essentially a shearing motion. Thermo-mechanical modelling of the DSB supports such a scenario. As the DESIRE seismic profile crosses the DST about 100 km north of where the DESERT seismic profile crosses the DST, it has been possible to construct a crustal cross-section of the region before the 107 km left-lateral shear on the DST occurred.
Y1  - 2009
UR  - http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-246X
U6  - https://doi.org/10.1111/j.1365-246X.2009.04161.x
SN  - 0956-540X
ER  - 
TY  - JOUR
A1  - Mohsen, Ayman
A1  - Asch, Günter
A1  - Kind, Rainer
A1  - Mechie, James
A1  - Weber, Michael H.
T1  - The lithosphere-asthenosphere boundary in the eastern part of the Dead Sea Basin (DSB) from S-to-P receiver functions
JF  - Arabian journal of geosciences
N2  - Clear S-to-P converted waves from the crust-mantle boundary (Moho) and lithosphere-asthenosphere boundary (LAB) have been observed on the eastern part of the Dead Sea Basin (DSB), and are used for the determination of the depth of the Moho and the LAB. A temporary network consisting of 18 seismic broad-band stations was operated in the DSB region as part of the DEad Sea Integrated REsearch project for 1.5 years beginning in September 2006. The obtained Moho depth (similar to 35 km) from S-to-P receiver functions agrees well with the results from P-to-S receiver functions and other geophysical data. The thickness of the lithosphere on the eastern part of the DSB is about 75 km. The results obtained here support and confirm previous studies, based on xenolith data, geodynamic modeling, heat flow observations, and S-to-P receiver functions. Therefore, the lithosphere on the eastern part of the DSB and along Wadi Araba has been thinned in the Late Cenozoic, following rifting and spreading of the Red Sea. The thinning of the lithosphere occurred without a concomitant change in the crustal thickness and thus an upwelling of the asthenosphere in the study area is invoked as the cause of the lithosphere thinning.
KW  - Dead Sea basin
KW  - S receiver functions
KW  - Lithosphere
Y1  - 2013
U6  - https://doi.org/10.1007/s12517-011-0503-4
SN  - 1866-7511
SN  - 1866-7538
VL  - 6
IS  - 7
SP  - 2343
EP  - 2350
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Mohsen, Amjad
A1  - Asch, Günter
A1  - Mechie, James
A1  - Kind, Rainer
A1  - Hofstetter, Rami
A1  - Weber, Michael H.
A1  - Stiller, M.
A1  - Abu-Ayyash, Khalil
T1  - Crustal structure of the Dead Sea Basin (DSB) from a receiver function analysis
JF  - Geophysical journal international
N2  - The Dead Sea Transform (DST) is a major left-lateral strike-slip fault that accommodates the relative motion between the African and Arabian plates, connecting a region of extension in the Red Sea to the Taurus collision zone in Turkey over a length of about 1100 km. The Dead Sea Basin (DSB) is one of the largest basins along the DST. The DSB is a morphotectonic depression along the DST, divided into a northern and a southern sub-basin, separated by the Lisan salt diapir. We report on a receiver function study of the crust within the multidisciplinary geophysical project, DEad Sea Integrated REsearch (DESIRE), to study the crustal structure of the DSB. A temporary seismic network was operated on both sides of the DSB between 2006 October and 2008 April. The aperture of the network is approximately 60 km in the E-W direction crossing the DSB on the Lisan peninsula and about 100 km in the N-S direction. Analysis of receiver functions from the DESIRE temporary network indicates that Moho depths vary between 30 and 38 km beneath the area. These Moho depth estimates are consistent with results of near-vertical incidence and wide-angle controlled-source techniques. Receiver functions reveal an additional discontinuity in the lower crust, but only in the DSB and west of it. This leads to the conclusion that the internal crustal structure east and west of the DSB is different at the present-day. However, if the 107 km left-lateral movement along the DST is taken into account, then the region beneath the DESIRE array where no lower crustal discontinuity is observed would have lain about 18 Ma ago immediately adjacent to the region under the previous DESERT array west of the DST where no lower crustal discontinuity is recognized.
KW  - Transform faults
KW  - Crustal structure
Y1  - 2011
U6  - https://doi.org/10.1111/j.1365-246X.2010.04853.x
SN  - 0956-540X
VL  - 184
IS  - 1
SP  - 463
EP  - 476
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Ramos, C.
A1  - Mechie, James
A1  - Feng, M.
T1  - Shear wave velocity and Poisson's ratio models across the southern Chile convergent margin at 38°15′S
JF  - Geophysical journal international
N2  - Using active and passive seismology data we derive a shear (S) wave velocity model and a Poisson's ratio (σ) model across the Chilean convergent margin along a profile at 38°15′S, where the Mw 9.5 Valdivia earthquake occurred in 1960. The derived S-wave velocity model was constructed using three independently obtained velocity models that were merged together. In the upper part of the profile (0–2 km depth), controlled source data from explosions were used to obtain an S-wave traveltime tomogram. For the middle part (2–20 km depth), data from a temporary seismology array were used to carry out a dispersion analysis. The resulting dispersion curves were used to obtain a 3-D S-wave velocity model. In the lower part (20–75 km depth, depending on the longitude), an already existent local earthquake tomographic image was merged with the other two sections. This final S-wave velocity model and already existent compressional (P) wave velocity models along the same transect allowed us to obtain a Poisson's ratio model. The results of this study show that the velocities and Poisson's ratios in the continental crust of this part of the Chilean convergent margin are in agreement with geological features inferred from other studies and can be explained in terms of normal rock types. There is no requirement to call on the existence of measurable amounts of present-day fluids, in terms of seismic velocities, above the plate interface in the continental crust of the Coastal Cordillera and the Central Valley in this part of the Chilean convergent margin. This is in agreement with a recent model of water being transported down and released from the subduction zone.
KW  - Controlled source seismology
KW  - Seismic tomography
KW  - Computational seismology
KW  - South America
Y1  - 2016
U6  - https://doi.org/10.1093/gji/ggv541
SN  - 0956-540X
SN  - 1365-246X
VL  - 204
SP  - 1620
EP  - 1635
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Oncken, Onno
A1  - Luschen, Ewald
A1  - Mechie, James
A1  - Sobolev, Stephan Vladimir
A1  - Schulze, Albrecht
A1  - Gaedicke, Christoph
A1  - Grunewald, Steffen
A1  - Bribach, Jens
A1  - Asch, Günter
A1  - Giese, Peter
A1  - Wigger, Peter
A1  - Schmitz, Michael
A1  - Lueth, Stefan
A1  - Scheuber, Ekkehard
A1  - Haberland, Christian
A1  - Rietbrock, Andreas
A1  - Götze, Hans-Jürgen
A1  - Brasse, Heinrich
A1  - Patzwahl, Regina
A1  - Chong, Guillermo
A1  - Wilke, Hans-Gerhard
A1  - Gonzalez, Gabriel
A1  - Jensen, Arturo
A1  - Araneda, Manuel
A1  - Vieytes, Hugo
A1  - Behn, Gerardo
A1  - Martinez, Eloy
T1  - Seismic reflection image revealing offset of Andean subduction-zone earthquake locations into oceanic mantle
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Dahm, Torsten
A1  - Stiller, Manfred
A1  - Mechie, James
A1  - Heimann, Sebastian
A1  - Hensch, Martin
A1  - Woith, Heiko
A1  - Schmidt, Bernd
A1  - Gabriel, Gerald
A1  - Weber, Michael
T1  - Seismological and geophysical signatures of the deep crustal magma systems of the cenozoic volcanic fields Beneath the Eifel, Germany
JF  - Geochemistry, geophysics, geosystems
N2  - The Quaternary volcanic fields of the Eifel (Rhineland-Palatinate, Germany) had their last eruptions less than 13,000 years ago. Recently, deep low-frequency (DLF) earthquakes were detected beneath one of the volcanic fields showing evidence of ongoing magmatic activity in the lower crust and upper mantle. In this work, seismic wide- and steep-angle experiments from 1978/1979 and 1987/1988 are compiled, partially reprocessed and interpreted, together with other data to better determine the location, size, shape, and state of magmatic reservoirs in the Eifel region near the crust-mantle boundary. We discuss seismic evidence for a low-velocity gradient layer from 30-36 km depth, which has developed over a large region under all Quaternary volcanic fields of the Rhenish Massif and can be explained by the presence of partial melts. We show that the DLF earthquakes connect the postulated upper mantle reservoir with the upper crust at a depth of about 8 km, directly below one of the youngest phonolitic volcanic centers in the Eifel, where CO(2)originating from the mantle is massively outgassing. A bright spot in the West Eifel between 6 and 10 km depth represents a Tertiary magma reservoir and is seen as a model for a differentiated reservoir beneath the young phonolitic center today. We find that the distribution of volcanic fields is controlled by the Variscan lithospheric structures and terrane boundaries as a whole, which is reflected by an offset of the Moho depth, a wedge-shaped transparent zone in the lower crust and the system of thrusts over about 120 km length.
KW  - magma reservoirs
KW  - distributed volcanic fields
KW  - reflection seismic
KW  - crustal magma chamber
KW  - deep low-frequency earthquakes
KW  - low velocity zone
Y1  - 2020
U6  - https://doi.org/10.1029/2020GC009062
SN  - 1525-2027
VL  - 21
IS  - 9
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Weber, Michael H.
A1  - Abu-Ayyash, Khalil
A1  - Abueladas, Abdel-Rahman
A1  - Agnon, Amotz
A1  - Al-Amoush, H.
A1  - Babeyko, Andrey
A1  - Bartov, Yosef
A1  - Baumann, M.
A1  - Ben-Avraham, Zvi
A1  - Bock, Günter
A1  - Bribach, Jens
A1  - El-Kelani, R.
A1  - Forster, A.
A1  - Förster, Hans-Jürgen
A1  - Frieslander, U.
A1  - Garfunkel, Zvi
A1  - Grunewald, Steffen
A1  - Gotze, Hans-Jürgen
A1  - Haak, Volker
A1  - Haberland, Christian
A1  - Hassouneh, Mohammed
A1  - Helwig, S.
A1  - Hofstetter, Alfons
A1  - Jackel, K. H.
A1  - Kesten, Dagmar
A1  - Kind, Rainer
A1  - Maercklin, Nils
A1  - Mechie, James
A1  - Mohsen, Amjad
A1  - Neubauer, F. M.
A1  - Oberhänsli, Roland
A1  - Qabbani, I.
A1  - Ritter, O.
A1  - Rumpker, G.
A1  - Rybakov, M.
A1  - Ryberg, Trond
A1  - Scherbaum, Frank
A1  - Schmidt, J.
A1  - Schulze, A.
A1  - Sobolev, Stephan Vladimir
A1  - Stiller, M.
A1  - Th, 
T1  - The crustal structure of the Dead Sea Transform
N2  - To address one of the central questions of plate tectonics-How do large transform systems work and what are their typical features?-seismic investigations across the Dead Sea Transform (DST), the boundary between the African and Arabian plates in the Middle East, were conducted for the first time. A major component of these investigations was a combined reflection/ refraction survey across the territories of Palestine, Israel and Jordan. The main results of this study are: (1) The seismic basement is offset by 3-5 km under the DST, (2) The DST cuts through the entire crust, broadening in the lower crust, (3) Strong lower crustal reflectors are imaged only on one side of the DST, (4) The seismic velocity sections show a steady increase in the depth of the crust-mantle transition (Moho) from 26 km at the Mediterranean to 39 km under the Jordan highlands, with only a small but visible, asymmetric topography of the Moho under the DST. These observations can be linked to the left-lateral movement of 105 km of the two plates in the last 17 Myr, accompanied by strong deformation within a narrow zone cutting through the entire crust. Comparing the DST and the San Andreas Fault (SAF) system, a strong asymmetry in subhorizontal lower crustal reflectors and a deep reaching deformation zone both occur around the DST and the SAF. The fact that such lower crustal reflectors and deep deformation zones are observed in such different transform systems suggests that these structures are possibly fundamental features of large transform plate boundaries
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Sippel, Judith
A1  - Meessen, Christian
A1  - Cacace, Mauro
A1  - Mechie, James
A1  - Fishwick, Stewart
A1  - Heine, Christian
A1  - Scheck-Wenderoth, Magdalena
A1  - Strecker, Manfred
T1  - The Kenya rift revisited
BT  - insights into lithospheric strength through data-driven 3-D gravity and thermal modelling
JF  - Solid earth
N2  - We present three-dimensional (3-D) models that describe the present-day thermal and rheological state of the lithosphere of the greater Kenya rift region aiming at a better understanding of the rift evolution, with a particular focus on plume-lithosphere interactions. The key methodology applied is the 3-D integration of diverse geological and geophysical observations using gravity modelling. Accordingly, the resulting lithospheric-scale 3-D density model is consistent with (i) reviewed descriptions of lithological variations in the sedimentary and volcanic cover, (ii) known trends in crust and mantle seismic velocities as revealed by seismic and seismological data and (iii) the observed gravity field. This data-based model is the first to image a 3-D density configuration of the crystalline crust for the entire region of Kenya and northern Tanzania. An upper and a basal crustal layer are differentiated, each composed of several domains of different average densities. We interpret these domains to trace back to the Precambrian terrane amalgamation associated with the East African Orogeny and to magmatic processes during Mesozoic and Cenozoic rifting phases. In combination with seismic velocities, the densities of these crustal domains indicate compositional differences. The derived lithological trends have been used to parameterise steady-state thermal and rheological models. These models indicate that crustal and mantle temperatures decrease from the Kenya rift in the west to eastern Kenya, while the integrated strength of the lithosphere increases. Thereby, the detailed strength configuration appears strongly controlled by the complex inherited crustal structure, which may have been decisive for the onset, localisation and propagation of rifting.
Y1  - 2017
U6  - https://doi.org/10.5194/se-8-45-2017
SN  - 1869-9510
SN  - 1869-9529
VL  - 8
SP  - 45
EP  - 81
PB  - Copernicus
CY  - Göttingen
ER  -