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 - Weber, Michael H. A1 - Wicks, Charles A1 - Le Stunff, Yves A1 - Romanowicz, Barbara A1 - Krüger, Frank T1 - Seismic evidence for a steeply dipping reflector-stagnant slab in the mantle transition zone JF - Geophysical journal international N2 - Studies of seismic tomography have been highly successful at imaging the deep structure of subduction zones. In a study complementary to these tomographic studies, we use array seismology and reflected waves to image a stagnant slab in the mantle transition zone. Using P and S (SH) waves we find a steeply dipping reflector centred at ca. 400 km depth and ca. 550 km west of the present Mariana subduction zone (at 20N, 140E). The discovery of this anomaly in tomography and independently in array seismology (this paper) helps in understanding the evolution of the Mariana margin. The reflector/stagnant slab may be the remains of the hypothetical North New Guinea Plate, which was theorized to have subducted ca. 50 Ma. KW - Mantle processes KW - Composition of the mantle KW - Seismic tomography KW - Wave scattering and diffraction KW - Subduction zone processes KW - Volcanic arc processes KW - Continental margins: convergent KW - Pacific Ocean Y1 - 2015 U6 - https://doi.org/10.1093/gji/ggu438 SN - 0956-540X SN - 1365-246X VL - 200 IS - 2 SP - 1235 EP - 1251 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Lange, Dietrich A1 - Bedford, J. R. A1 - Moreno, M. A1 - Tilmann, F. A1 - Báez, Juan Carlos A1 - Bevis, M. A1 - Krüger, Frank T1 - Comparison of postseismic afterslip models with aftershock seismicity for three subduction-zone earthquakes: Nias 2005, Maule 2010 and Tohoku 2011 JF - Geophysical journal international N2 - We focus on the relation between seismic and total postseismic afterslip following the Maule M-w 8.8 earthquake on 2010 February 27 in central Chile. First, we calculate the cumulative slip released by aftershock seismicity. We do this by summing up the aftershock regions and slip estimated from scaling relations. Comparing the cumulative seismic slip with afterslip modelswe showthat seismic slip of individual aftershocks exceeds locally the inverted afterslip model from geodetic constraints. As the afterslip model implicitly contains the displacements from the aftershocks, this reflects the tendency of afterslip models to smear out the actual slip pattern. However, it also suggests that locally slip for a number of the larger aftershocks exceeds the aseismic slip in spite of the fact that the total equivalent moment of the afterslip exceeds the cumulative moment of aftershocks by a large factor. This effect, seen weakly for the Maule 2010 and also for the Tohoku 2011 earthquake, can be explained by taking into account the uncertainties of the seismicity and afterslip models. In spite of uncertainties, the hypocentral region of the Nias 2005 earthquake is suggested to release a large fraction of moment almost purely seismically. Therefore, these aftershocks are not driven solely by the afterslip but instead their slip areas have probably been stressed by interseismic loading and the mainshock rupture. In a second step, we divide the megathrust of the Maule 2010 rupture into discrete cells and count the number of aftershocks that occur within 50 km of the centre of each cell as a function of time. We then compare this number to a time-dependent afterslip model by defining the 'afterslip to aftershock ratio' (ASAR) for each cell as the slope of the best fitting line when the afterslip at time t is plotted against aftershock count. Although we find a linear relation between afterslip and aftershocks for most cells, there is significant variability in ASAR in both the downdip and along-strike directions of the megathrust. We compare the spatial distribution of ASAR with the spatial distribution of seismic coupling, coseismic slip and Bouguer gravity anomaly, and in each case we find no significant correlation. KW - Creep and deformation KW - Earthquake dynamics KW - Seismicity and tectonics KW - Continental margins: convergent Y1 - 2014 U6 - https://doi.org/10.1093/gji/ggu292 SN - 0956-540X SN - 1365-246X VL - 199 IS - 2 SP - 784 EP - 799 PB - Oxford Univ. Press CY - Oxford ER -