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 - 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 - Czuba, Wojciech A1 - Grad, Marek A1 - Mjelde, Rolf A1 - Guterch, Aleksander A1 - Libak, Audun A1 - Krüger, Frank A1 - Murai, Yoshio A1 - Schweitzer, Johannes T1 - Continent-ocean-transition across a trans-tensional margin segment: off Bear Island, Barents Sea JF - Geophysical journal international N2 - P>A 410 km long Ocean Bottom Seismometer profile spanning from the Bear Island, Barents Sea to oceanic crust formed along the Mohns Ridge has been modelled by use of ray-tracing with regard to observed P-waves. The northeastern part of the model represents typical continental crust, thinned from ca. 30 km thickness beneath the Bear Island to ca. 13 km within the Continent-Ocean-Transition. Between the Hornsund FZ and the Kn circle divide legga Fault, a 3-4 km thick sedimentary basin, dominantly of Permian/Carboniferous age, is modelled beneath the ca. 1.5 km thick layer of volcanics (Vestbakken Volcanic Province). The P-wave velocity in the 3-4 km thick lowermost continental crust is significantly higher than normal (ca. 7.5 km s-1). We interpret this layer as a mixture of mafic intrusions and continental crystalline blocks, dominantly related to the Paleocene-Early Eocene rifting event. The crystalline portion of the crust within the south-western part of the COT consists of a ca. 30 km wide and ca. 6 km thick high-velocity (7.3 km s-1) body. We interpret the body as a ridge of serpentinized peridotites. The magmatic portion of the ocean crust accreted along the Knipovich Ridge from continental break-up at ca. 35 Ma until ca. 20 Ma is 3-5 km thicker than normal. We interpret the increased magmatism as a passive response to the bending of this southernmost part of the Knipovich Ridge. The thickness of the magmatic portion of the crust formed along the Mohns Ridge at ca. 20 Ma decreases to ca. 3 km, which is normal for ultra slow spreading ridges. KW - Controlled source seismology KW - Dynamics of lithosphere and mantle KW - Crustal structure KW - Atlantic Ocean Y1 - 2011 U6 - https://doi.org/10.1111/j.1365-246X.2010.04873.x SN - 0956-540X VL - 184 IS - 2 SP - 541 EP - 554 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Paschke, Marco A1 - Stiller, Manfred A1 - Ryberg, Trond A1 - Weber, Michael H. T1 - The shallow P-velocity structure of the southern Dead Sea basin derived from near-vertical incidence reflection seismic data in project DESIRE JF - Geophysical journal international N2 - As a part of the DEad Sea Integrated REsearch (DESIRE) project a near-vertical incidence reflection (NVR) experiment with a profile length of 122 km was completed in spring 2006. The profile crossed the southern Dead Sea basin (DSB), a pull-apart basin due to the strike-slip motion along the Dead Sea Transform (DST). The DST with a total displacement of 107 km since about 18 Ma is part of a left-lateral fault system which connects the spreading centre in the Red Sea with the Taurus collision zone in Turkey over a distance of about 1100 km. The seismic experiment comprises 972 source locations and 1045 receiver locations. Each source was recorded by similar to 180 active receivers and a field data set with 175 000 traces was created. From this data set, 124 444 P-wave first-break traveltimes have been picked. With these traveltimes a tomographic inversion was carried out, resulting in a 2-D P-wave velocity model with a rms error of 20.9 ms. This model is dominated by a low-velocity region associated with the DSB. Within the DSB, the model shows clearly the position of the Lisan salt diapir, identified by a high-velocity zone. A further feature is an unexpected laterally low-velocity zone with P-velocities of 3 km s1 embedded in regions with 4 km s1 in the shallow part on the west side of the DSB. Another observation is an anticlinal structure west of the DSB interpretated to the related Syrian arc fold belt. KW - Tomography KW - Controlled source seismology KW - Transform faults Y1 - 2012 U6 - https://doi.org/10.1111/j.1365-246X.2011.05270.x SN - 0956-540X VL - 188 IS - 2 SP - 524 EP - 534 PB - Wiley-Blackwell CY - Malden ER -