The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Hossein Shomali - One of the best experts on this subject based on the ideXlab platform.
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upper mantle s velocity structure and moho depth variations across zagros belt arabian Eurasian Plate boundary
Physics of the Earth and Planetary Interiors, 2010Co-Authors: Navid Shad Manaman, Hossein ShomaliAbstract:The collision of the Arabian and Eurasian Plates in the early Miocene, after the subduction of Neo-Tethys ocean beneath Eurasia, formed the Zagros belt, a seismically active continental-continental Plate boundary in southwest Iran. The Zagros suture zone is an important seismotectonic boundary indicating an abrupt cutoff between the intense seismicity of the Zagros and the almost aseismic Central Iran Plateau. Compared with other more evolved Plate boundaries, little is known about the deep lithospheric structure of the Zagros belt, such as the fate of subducted Neo-Tethys Plate and ambiguity in the presence of intermediate and deep earthquakes under the Zagros suture zone. In this study, we use the partitioned waveform inversion (PWI) method to image the upper mantle S-velocity structure and Moho depth variations across Zagros collisional zone. The resulting Moho depth along the profile shows the average Moho depth value of order of 40-45 km for most parts of the profile with abrupt crustal thickening in the middle of the profile up to about 65 km. As expected, the derived models show that the relatively old and cold Arabian Plate has higher velocity at depth than the younger lithosphere farther north in Central Iran. A sharp and steep subcrustal boundary is found roughly coincident with the surficial expression of the Main Zagros Thrust (MZT), separating two different mantle domains. A high-velocity anomaly, possibly representing a fragment of subducted lithosphere, has been imaged beneath Central Iran at a depth between 350 and 600 km, which is quite similar to the case of Indo-Asian collision in Qinghai-Tibetan Plateau. These observations as well as the sudden changes of shallow velocities along the cross-section with a sharp boundary under the Zagros suture zone support the idea that subducted oceanic lithosphere has broken-off under the region of maximum Moho depth. A relatively low velocity region beneath the Arabian Plate is also imaged in our high resolution tomography model which is interpreted as an indication of lithospheric delamination within the Arabian lithosphere.
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surface waveform tomography across the arabian Eurasian Plate boundary zagros belt
71st EAGE Conference and Exhibition incorporating SPE EUROPEC 2009, 2009Co-Authors: Shad N Manaman, Hossein ShomaliAbstract:Compared with other more evolved Plate boundaries, little is known about the deep lithospheric structure of Zagros belt, such as fate of subducted Neo-Tethys Plate and existence of deeply earthquakes. We use the Partitioned Waveform Inversion method to im
Chienhsin Chang - One of the best experts on this subject based on the ideXlab platform.
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investigating the lithospheric velocity structures beneath the taiwan region by nonlinear joint inversion of local and teleseismic p wave data slab continuity and deflection
Geophysical Research Letters, 2014Co-Authors: Hsinhua Huang, Xiaodong Song, Chienhsin Chang, Hao Kuochen, Shiannjong LeeAbstract:The interaction between two flipping subduction systems shapes the complicated lithospheric structures and dynamics around the Taiwan region. Whether and in what form the Eurasian Plate subducts/deforms under Taiwan Island is critical to the debate of tectonic models. Although an east dipping high-velocity anomaly down to a depth below 200 km has been reported previously, its detailed morphology remains uncertain and leads to different interpretations. With a two-step strategy of nonlinear joint inversion, the slab images of the Eurasian Plate were retrieved in a geometry that is hyperthin in the south, becoming massive and steeper in the central, and severely deformed in the north. The possible depth and dimension of a slab break were also investigated through synthetic tests of whether the slab had torn. Moreover, the slab deflection found at ~23.2°N latitude seems to correspond to where the nonvolcanic tremors and recent NW-SE striking structures have occurred in southern Taiwan.
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investigating the lithospheric velocity structures beneath the taiwan region by nonlinear joint inversion of local and teleseismic p wave data slab continuity and deflection
Geophysical Research Letters, 2014Co-Authors: Hsinhua Huang, Xiaodong Song, Chienhsin Chang, Yihmin Wu, Hao KuochenAbstract:The interaction between two flipping subduction systems shapes the complicated lithospheric structures and dynamics around the Taiwan region. Whether and in what form the Eurasian Plate subducts/deforms under Taiwan Island is critical to the debate of tectonic models. Although an east dipping high-velocity anomaly down to a depth below 200 km has been reported previously, its detailed morphology remains uncertain and leads to different interpretations. With a two-step strategy of nonlinear joint inversion, the slab images of the Eurasian Plate were retrieved in a geometry that is hyperthin in the south, becoming massive and steeper in the central, and severely deformed in the north. The possible depth and dimension of a slab break were also investigated through synthetic tests of whether the slab had torn. Moreover, the slab deflection found at ~23.2°N latitude seems to correspond to where the nonvolcanic tremors and recent NW-SE striking structures have occurred in southern Taiwan.
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assessment of long term variation in displacement for a gps site adjacent to a transition zone between collision and subduction
Stochastic Environmental Research and Risk Assessment, 2008Co-Authors: David Chingfang Shih, Gwofong Lin, Yuegau Chen, Chienhsin ChangAbstract:A transition and subduction zone adjacent to the Ryukyu Arc, Ryukyu Trench, and Okinawa Trough, extends between southern Japan and northeastern Taiwan. It is generated during the northwestward subduction of the Philippine Sea Plate, which lies the Eurasian Plate along the Ryukyu Trench. The movement of the Philippine Sea Plate is hindered at the northeastern corner of Taiwan, which causes complicated structure of the Philippine Sea Plate at the western end of the Ryukyu subduction zone. Development of the active subduction and transition boundary near the western Ryukyu Arc is evaluated statistically by using displacements derived from GPS site data. The statistical model shows that the absolute displacement derived from GPS measurements of nearly 8 years indicates a maximum spatial variation of 0.625 m. Three trends are observed for such long-term progress, and use of linear regression also reveals quite good consistency between the data and statistic models. Such rate is also elevated following the trend development. Southeastern and nearly horizontal movement is suggested to the main development of for the site movements, it is likely related to the tensional activity adjacent to this boundary.
Hao Kuochen - One of the best experts on this subject based on the ideXlab platform.
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investigating the lithospheric velocity structures beneath the taiwan region by nonlinear joint inversion of local and teleseismic p wave data slab continuity and deflection
Geophysical Research Letters, 2014Co-Authors: Hsinhua Huang, Xiaodong Song, Chienhsin Chang, Hao Kuochen, Shiannjong LeeAbstract:The interaction between two flipping subduction systems shapes the complicated lithospheric structures and dynamics around the Taiwan region. Whether and in what form the Eurasian Plate subducts/deforms under Taiwan Island is critical to the debate of tectonic models. Although an east dipping high-velocity anomaly down to a depth below 200 km has been reported previously, its detailed morphology remains uncertain and leads to different interpretations. With a two-step strategy of nonlinear joint inversion, the slab images of the Eurasian Plate were retrieved in a geometry that is hyperthin in the south, becoming massive and steeper in the central, and severely deformed in the north. The possible depth and dimension of a slab break were also investigated through synthetic tests of whether the slab had torn. Moreover, the slab deflection found at ~23.2°N latitude seems to correspond to where the nonvolcanic tremors and recent NW-SE striking structures have occurred in southern Taiwan.
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investigating the lithospheric velocity structures beneath the taiwan region by nonlinear joint inversion of local and teleseismic p wave data slab continuity and deflection
Geophysical Research Letters, 2014Co-Authors: Hsinhua Huang, Xiaodong Song, Chienhsin Chang, Yihmin Wu, Hao KuochenAbstract:The interaction between two flipping subduction systems shapes the complicated lithospheric structures and dynamics around the Taiwan region. Whether and in what form the Eurasian Plate subducts/deforms under Taiwan Island is critical to the debate of tectonic models. Although an east dipping high-velocity anomaly down to a depth below 200 km has been reported previously, its detailed morphology remains uncertain and leads to different interpretations. With a two-step strategy of nonlinear joint inversion, the slab images of the Eurasian Plate were retrieved in a geometry that is hyperthin in the south, becoming massive and steeper in the central, and severely deformed in the north. The possible depth and dimension of a slab break were also investigated through synthetic tests of whether the slab had torn. Moreover, the slab deflection found at ~23.2°N latitude seems to correspond to where the nonvolcanic tremors and recent NW-SE striking structures have occurred in southern Taiwan.
Dapeng Zhao - One of the best experts on this subject based on the ideXlab platform.
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Seismic anisotropy and mantle dynamics beneath China
Earth and Planetary Science Letters, 2011Co-Authors: Zhouchuan Huang, Liangshu Wang, Dapeng ZhaoAbstract:Abstract We analyzed the shear-wave splitting at 138 permanent seismograph stations to study seismic anisotropy and mantle dynamics under Mainland China. To obtain reliable results we used three different methods to measure the shear-wave splitting parameters using core phases (SKS, SKKS, SKiKS and PKS) as well as the direct S waves from regional and distant earthquakes. Our results show that the fast orientations of the anisotropy (WNW–ESE) in eastern China are generally consistent with the absolute Plate motion (APM) direction of the Eurasian Plate, suggesting that the anisotropy is mainly located in the asthenosphere resulting from the lattice-preferred orientation of olivine due to the shear deformation there. The fast axes in western China generally agree with the strikes of the orogens and active faults, while they are perpendicular to the direction of the maximum horizontal stress, suggesting that the anisotropy in the lithosphere contributes significantly to the observed shear-wave splitting. The fast axes in western China are also consistent with the APM direction, suggesting that the APM-driven anisotropy in the asthenosphere is another source of the shear-wave splitting there. These results suggest that APM-driven anisotropy commonly exists under continents, similar to that under oceanic regions, even though the continental lithosphere has suffered extensive deformation.
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new seismic constraints on the upper mantle structure of the hainan plume
Physics of the Earth and Planetary Interiors, 2009Co-Authors: Jianshe Lei, Dapeng Zhao, Bernhard Steinberger, Fanluan ShenAbstract:Abstract We present a high-resolution tomographic image in the upper mantle for the Hainan plume determined by using both local and teleseismic data. The arrival-time data from teleseismic events are measured precisely from seismograms recorded by nine permanent seismic stations in Hainan island and Leizhou peninsula. Our results show that striking low-velocity (low-V) anomalies of up to −5% in the crust and −2% in the mantle are visible under the Hainan hotspot from the surface down to 250 km depth. The Hainan plume is imaged as a continuous, NW–SE tilting, low-V column with a diameter of about 80 km. Given the denser data coverage and finer parameterization, our result represents a significant improvement with respect to earlier, regional and global tomographic studies. Such an inclination of the Hainan plume can be explained by numerical simulations. The tilted plume conduit in the upper mantle could be associated with the subduction of oceanic Plates, especially the Philippine Sea Plate, and the extrusion of the Eurasian Plate. Most likely, the tilted plume conduit has buoyantly risen from the lower mantle.
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lithospheric structure and its relationship to seismic and volcanic activity in southwest china
Journal of Geophysical Research, 2002Co-Authors: Jinli Huang, Dapeng Zhao, Sihua ZhengAbstract:[1] The Sichuan-Yunnan region in southwest China is located in the boundary area between the active Tibetan Plateau to the west and the stable South China platform to the east. This region is characterized by complex Cenozoic structures and active seismotectonics. In this study, we have used over 30,000 arrival times from 1315 local earthquakes recorded by 172 seismic stations to determine a detailed three-dimensional (3-D) P wave velocity structure of the lithosphere down to 85 km depth in this region. We have taken into account the complex morphology of the Moho discontinuity to conduct the tomographic inversions, which leads to a better result than that with a flat Moho as in the previous studies. Our results show that large velocity variations of up to 7% exist in the crust and upper mantle in the Sichuan-Yunnan region. The velocity image of the upper crust correlates with the surface geological features. The Sichuan basin is imaged as a prominent low-velocity zone, while the Panzhihua mining district is imaged as a high-velocity feature. Velocity changes are visible across some of the large fault zones, and the faults and some large crustal earthquakes seem to occur at the boundary areas between slow and fast velocity anomalies. Some of the faults, such as the Red River fault, may have cut through the crust and reached up to the upper mantle. Under the Tengchong volcanic area, strong low-velocity zones are visible down to 85 km depth, with a lateral extent of about 100 km, suggesting the existence of magma chambers under the volcano. It is unclear how the Tengchong intraPlate volcanism was generated. It may be related to the collision processes between the Indian Plate, Burma microPlate and the Eurasian Plate, and the possible subduction of the Burma microPlate under the Eurasian Plate. Another possibility is that it was caused by the extensional fractures of the lithosphere and the upward intrusion of the hot asthenospheric materials. It is also possible that the Tengchong volcanism represents a hot spot with a lower mantle origin.
Hsinhua Huang - One of the best experts on this subject based on the ideXlab platform.
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investigating the lithospheric velocity structures beneath the taiwan region by nonlinear joint inversion of local and teleseismic p wave data slab continuity and deflection
Geophysical Research Letters, 2014Co-Authors: Hsinhua Huang, Xiaodong Song, Chienhsin Chang, Hao Kuochen, Shiannjong LeeAbstract:The interaction between two flipping subduction systems shapes the complicated lithospheric structures and dynamics around the Taiwan region. Whether and in what form the Eurasian Plate subducts/deforms under Taiwan Island is critical to the debate of tectonic models. Although an east dipping high-velocity anomaly down to a depth below 200 km has been reported previously, its detailed morphology remains uncertain and leads to different interpretations. With a two-step strategy of nonlinear joint inversion, the slab images of the Eurasian Plate were retrieved in a geometry that is hyperthin in the south, becoming massive and steeper in the central, and severely deformed in the north. The possible depth and dimension of a slab break were also investigated through synthetic tests of whether the slab had torn. Moreover, the slab deflection found at ~23.2°N latitude seems to correspond to where the nonvolcanic tremors and recent NW-SE striking structures have occurred in southern Taiwan.
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investigating the lithospheric velocity structures beneath the taiwan region by nonlinear joint inversion of local and teleseismic p wave data slab continuity and deflection
Geophysical Research Letters, 2014Co-Authors: Hsinhua Huang, Xiaodong Song, Chienhsin Chang, Yihmin Wu, Hao KuochenAbstract:The interaction between two flipping subduction systems shapes the complicated lithospheric structures and dynamics around the Taiwan region. Whether and in what form the Eurasian Plate subducts/deforms under Taiwan Island is critical to the debate of tectonic models. Although an east dipping high-velocity anomaly down to a depth below 200 km has been reported previously, its detailed morphology remains uncertain and leads to different interpretations. With a two-step strategy of nonlinear joint inversion, the slab images of the Eurasian Plate were retrieved in a geometry that is hyperthin in the south, becoming massive and steeper in the central, and severely deformed in the north. The possible depth and dimension of a slab break were also investigated through synthetic tests of whether the slab had torn. Moreover, the slab deflection found at ~23.2°N latitude seems to correspond to where the nonvolcanic tremors and recent NW-SE striking structures have occurred in southern Taiwan.
