The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Nina I Pavlenkova - One of the best experts on this subject based on the ideXlab platform.
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the yamal peninsula lake baikal Deep Seismic Sounding profile
Geophysical Research Letters, 1993Co-Authors: John J Cipar, A V Egorkin, Keith Priestley, Nina I PavlenkovaAbstract:Seismograms from three nuclear explosions recorded along a 2400-km long Deep Seismic Sounding profile extending from the Yamal Peninsula to Lake Baikal are presented. We have constructed a preliminary 1-D compressional velocity model to fit the major travel time features of the data. Clear differences between the seismograms from each shot imply that the velocity structure of the crust and upper mantle is variable along the profile. Estimated crustal thicknesses range from 47 km beneath the west Siberian rift to 42 km beneath the Siberian craton. The structure of the upper mantle above the transition zone consists of material with P-wave velocities ranging from 8.25 km/s at the Moho to 8.53 km/s at 225 km. Velocities increase abruptly at 225-km depth to 8.63 km/s. There is little evidence for a pronounced low-velocity zone, although small velocity reversals are required to terminate several branches of the travel time curve. The uppermantle transition zone discontinuity at 425-km depth consists of a 5.6% first-order velocity increase. The lower discontinuity has a 4.9% velocity increase over the depth range 656.5 to 659 km.
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The Yamal Peninsula‐Lake Baikal Deep Seismic Sounding profile
Geophysical Research Letters, 1993Co-Authors: John J Cipar, A V Egorkin, Keith Priestley, Nina I PavlenkovaAbstract:Seismograms from three nuclear explosions recorded along a 2400-km long Deep Seismic Sounding profile extending from the Yamal Peninsula to Lake Baikal are presented. We have constructed a preliminary 1-D compressional velocity model to fit the major travel time features of the data. Clear differences between the seismograms from each shot imply that the velocity structure of the crust and upper mantle is variable along the profile. Estimated crustal thicknesses range from 47 km beneath the west Siberian rift to 42 km beneath the Siberian craton. The structure of the upper mantle above the transition zone consists of material with P-wave velocities ranging from 8.25 km/s at the Moho to 8.53 km/s at 225 km. Velocities increase abruptly at 225-km depth to 8.63 km/s. There is little evidence for a pronounced low-velocity zone, although small velocity reversals are required to terminate several branches of the travel time curve. The uppermantle transition zone discontinuity at 425-km depth consists of a 5.6% first-order velocity increase. The lower discontinuity has a 4.9% velocity increase over the depth range 656.5 to 659 km.
Walter D Mooney - One of the best experts on this subject based on the ideXlab platform.
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crustal p wave velocity structure beneath the se margin of the tibetan plateau from Deep Seismic Sounding results
Tectonophysics, 2019Co-Authors: Walter D Mooney, Tao Xu, Fuyun Wang, Yonghong Duan, Xiaofeng Tian, Youguo DengAbstract:Abstract The crust and uppermost mantle beneath the southeastern (SE) margin of Tibetan Plateau record the lateral expansion of Tibet and far-field effects from the ongoing continental collision and convergence. In order to obtain constraints on the Deep structure and the eastward expansion of the plateau, we synthesized Deep Seismic Sounding (DSS) results in this region and constructed the P wave velocity models for each terrane. The principal characteristics of the crustal velocity model and tectonic significance are: (1) Crustal thickness decreases from 53 km beneath the Songpan-Ganzi terrane (SGT) to 34 km in the south direction beneath Simao terrane (SMT), and 42 km in the east direction beneath Chengdu area. The crust is dominantly felsic in upper crust, with a small percentage of mafic composition in the lower crust. (2) The crustal structure is very heterogeneous in this region. The Indochina Block is characterized by low Seismic velocities in the upper crust, while the west Yangtze terrane (WYZT) and SGT show higher velocities in the upper crust. The lower crust beneath WYZT is relatively thicker than other terranes. (3) We deduce that the high velocity in the upper crust and relatively thick lower crust beneath the SGT and WYZT can be associated with magmatic processes that generated the Emeishan flood basalts which may have been triggered by rifting or mantle plume. The lateral variations of the crustal thickness in SE Tibet may be due to lower crustal flow from the Tibetan Plateau to the SE direction after blocked by the cold and rigid Yangtze craton in the east direction.
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crustal structure of mainland china from Deep Seismic Sounding data
Tectonophysics, 2006Co-Authors: Songlin Li, Walter D MooneyAbstract:Abstract Since 1958, about ninety Seismic refraction/wide angle reflection profiles, with a cumulative length of more than sixty thousand kilometers, have been completed in mainland China. We summarize the results in the form of (1) a new contour map of crustal thickness, (2) fourteen representative crustal Seismic velocity–depth columns for various tectonic units, and, (3) a Pn velocity map. We found a north–south-trending belt with a strong lateral gradient in crustal thickness in central China. This belt divides China into an eastern region, with a crustal thickness of 30–45 km, and a western region, with a thickness of 45–75 km. The crust in these two regions has experienced different evolutionary processes, and currently lies within distinct tectonic stress fields. Our compilation finds that there is a high-velocity (7.1–7.4 km/s) layer in the lower crust of the stable Tarim basin and Ordos plateau. However, in young orogenic belts, including parts of eastern China, the Tianshan and the Tibetan plateau, this layer is often absent. One exception is southern Tibet, where the presence of a high-velocity layer is related to the northward injection of the cold Indian plate. This high-velocity layer is absent in northern Tibet. In orogenic belts, there usually is a low-velocity layer (LVL) in the crust, but in stable regions this layer seldom exists. The Pn velocities in eastern China generally range from 7.9 to 8.1 km/s and tend to be isotropic. Pn velocities in western China are more variable, ranging from 7.7 to 8.2 km/s, and may display azimuthal anisotropy.
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crustal structure of china from Deep Seismic Sounding profiles
Tectonophysics, 1998Co-Authors: Songlin Li, Walter D MooneyAbstract:Abstract More than 36,000 km of Deep Seismic Sounding (DSS) profiles have been collected in China since 1958. However, the results of these profiles are not well known in the West due to the language barrier. In this paper, we summarize the crustal structure of China with a new contour map of crustal thickness, nine representative crustal columns, and maps showing profile locations, average crustal velocity, and Pn velocity. The most remarkable aspect of the crustal structure of China is the well known 70+ km thickness of the crust of the Tibetan Plateau. The thick (45–70 km) crust of western China is separated from the thinner (30–45 km) crust of eastern China by the north-south trending Seismic belt (105°E). The average crustal velocity of China ranges from 6.15 to 6.45 km/s, indicating a felsic-to-intermediate bulk crustal composition. Upper mantle (Pn) velocities are 8.0 ± 0.2 km/s, equal to the global continental average. We interpret these results in terms of the most recent thermo-tectonic events that have modified the crust. In much of eastern China, Cenozoic crustal extension has produced a thin crust with a low average crustal velocity, similar to western Europe and the Basin and Range Province, western USA. In western China, Mesozoic and Cenozoic arc-continent and continent-continent collisions have led to crustal growth and thickening. Inferences on the process of crustal thickening are provided by the Deep crustal velocity structure as determined by DSS profiles and other seismological studies. A high velocity (7.0–7.4 km/s) lower-crustal layer has been reported in western China only beneath the southernmost Tibetan Plateau. We identify this high-velocity layer as the cold lower crust of the subducting Indian plate. As the Indian crust is injected northward into the Tibetan lower crust, it heats and assimilates by partial melting, a process that results in a reduction in the Seismic velocity of the lower crust in the central and northern Tibetan Plateau.
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Deep Seismic Sounding in northern eurasia
Eos Transactions American Geophysical Union, 1992Co-Authors: Harley M Benz, J D Unger, William Leith, Walter D Mooney, L Solodilov, A V Egorkin, V Z RyaboyAbstract:For nearly 40 years, the former Soviet Union has carried out an extensive program of Seismic studies of the Earth's crust and upper mantle, known as “Deep Seismic Sounding” or DSS [Piwinskii, 1979; Zverev and Kosminskaya, 1980; Egorkin and Pavlenkova, 1981; Egorkin and Chernyshov, 1983; Scheimer and Borg, 1985]. Beginning in 1939–1940 with a series of small-scale Seismic experiments near Moscow, DSS profiling has broadened into a national multiinstitutional exploration effort that has completed almost 150,000 km of profiles covering all major geological provinces of northern Eurasia [Ryaboy, 1989].
John J Cipar - One of the best experts on this subject based on the ideXlab platform.
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the yamal peninsula lake baikal Deep Seismic Sounding profile
Geophysical Research Letters, 1993Co-Authors: John J Cipar, A V Egorkin, Keith Priestley, Nina I PavlenkovaAbstract:Seismograms from three nuclear explosions recorded along a 2400-km long Deep Seismic Sounding profile extending from the Yamal Peninsula to Lake Baikal are presented. We have constructed a preliminary 1-D compressional velocity model to fit the major travel time features of the data. Clear differences between the seismograms from each shot imply that the velocity structure of the crust and upper mantle is variable along the profile. Estimated crustal thicknesses range from 47 km beneath the west Siberian rift to 42 km beneath the Siberian craton. The structure of the upper mantle above the transition zone consists of material with P-wave velocities ranging from 8.25 km/s at the Moho to 8.53 km/s at 225 km. Velocities increase abruptly at 225-km depth to 8.63 km/s. There is little evidence for a pronounced low-velocity zone, although small velocity reversals are required to terminate several branches of the travel time curve. The uppermantle transition zone discontinuity at 425-km depth consists of a 5.6% first-order velocity increase. The lower discontinuity has a 4.9% velocity increase over the depth range 656.5 to 659 km.
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The Yamal Peninsula‐Lake Baikal Deep Seismic Sounding profile
Geophysical Research Letters, 1993Co-Authors: John J Cipar, A V Egorkin, Keith Priestley, Nina I PavlenkovaAbstract:Seismograms from three nuclear explosions recorded along a 2400-km long Deep Seismic Sounding profile extending from the Yamal Peninsula to Lake Baikal are presented. We have constructed a preliminary 1-D compressional velocity model to fit the major travel time features of the data. Clear differences between the seismograms from each shot imply that the velocity structure of the crust and upper mantle is variable along the profile. Estimated crustal thicknesses range from 47 km beneath the west Siberian rift to 42 km beneath the Siberian craton. The structure of the upper mantle above the transition zone consists of material with P-wave velocities ranging from 8.25 km/s at the Moho to 8.53 km/s at 225 km. Velocities increase abruptly at 225-km depth to 8.63 km/s. There is little evidence for a pronounced low-velocity zone, although small velocity reversals are required to terminate several branches of the travel time curve. The uppermantle transition zone discontinuity at 425-km depth consists of a 5.6% first-order velocity increase. The lower discontinuity has a 4.9% velocity increase over the depth range 656.5 to 659 km.
Tao Xu - One of the best experts on this subject based on the ideXlab platform.
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crustal p wave velocity structure beneath the se margin of the tibetan plateau from Deep Seismic Sounding results
Tectonophysics, 2019Co-Authors: Walter D Mooney, Tao Xu, Fuyun Wang, Yonghong Duan, Xiaofeng Tian, Youguo DengAbstract:Abstract The crust and uppermost mantle beneath the southeastern (SE) margin of Tibetan Plateau record the lateral expansion of Tibet and far-field effects from the ongoing continental collision and convergence. In order to obtain constraints on the Deep structure and the eastward expansion of the plateau, we synthesized Deep Seismic Sounding (DSS) results in this region and constructed the P wave velocity models for each terrane. The principal characteristics of the crustal velocity model and tectonic significance are: (1) Crustal thickness decreases from 53 km beneath the Songpan-Ganzi terrane (SGT) to 34 km in the south direction beneath Simao terrane (SMT), and 42 km in the east direction beneath Chengdu area. The crust is dominantly felsic in upper crust, with a small percentage of mafic composition in the lower crust. (2) The crustal structure is very heterogeneous in this region. The Indochina Block is characterized by low Seismic velocities in the upper crust, while the west Yangtze terrane (WYZT) and SGT show higher velocities in the upper crust. The lower crust beneath WYZT is relatively thicker than other terranes. (3) We deduce that the high velocity in the upper crust and relatively thick lower crust beneath the SGT and WYZT can be associated with magmatic processes that generated the Emeishan flood basalts which may have been triggered by rifting or mantle plume. The lateral variations of the crustal thickness in SE Tibet may be due to lower crustal flow from the Tibetan Plateau to the SE direction after blocked by the cold and rigid Yangtze craton in the east direction.
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Unusually thickened crust beneath the Emeishan large igneous province detected by virtual Deep Seismic Sounding
Tectonophysics, 2017Co-Authors: Xiaobo Tian, Javed Iqbal, Xiaofeng Liang, Tao Xu, Yun Chen, Yigang XuAbstract:Abstract The Emeishan Large Igneous Province (ELIP) in southwest China represents the erosional remnant of a vast basalt field emplaced during the Permian Period. Spanning 0.25 million km2, the ELIP occupies a relatively small area relative to other Large Igneous Provinces (LIPs) such as the Siberian Traps and Ontong Java Plateau. The original volume of an ancient LIP can be constrained from estimates of its intrusive component. We used virtual Deep Seismic Sounding (VDSS) to detect the boundary between the crust and the upper mantle (Moho) beneath the ELIP. A strong set of reflections from depths of 60–70 km indicate an unusually thick crust having a P-wave velocity of 7.0–7.4 km/s located beneath the inner zone of the ELIP. A high-velocity lower crustal body (HVLCB) of this thickness may have been formed by ponding magmas derived from the Emeishan mantle plume and associated fractionated materials. Combined images of crustal structure allow re-estimation of Emeishan magmatic volume. With a total estimated volume of 1.76–3.2 × 106 km3, the ELIP appears to have been a typical sized plume-generated LIP relative to other global examples.
Youguo Deng - One of the best experts on this subject based on the ideXlab platform.
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crustal p wave velocity structure beneath the se margin of the tibetan plateau from Deep Seismic Sounding results
Tectonophysics, 2019Co-Authors: Walter D Mooney, Tao Xu, Fuyun Wang, Yonghong Duan, Xiaofeng Tian, Youguo DengAbstract:Abstract The crust and uppermost mantle beneath the southeastern (SE) margin of Tibetan Plateau record the lateral expansion of Tibet and far-field effects from the ongoing continental collision and convergence. In order to obtain constraints on the Deep structure and the eastward expansion of the plateau, we synthesized Deep Seismic Sounding (DSS) results in this region and constructed the P wave velocity models for each terrane. The principal characteristics of the crustal velocity model and tectonic significance are: (1) Crustal thickness decreases from 53 km beneath the Songpan-Ganzi terrane (SGT) to 34 km in the south direction beneath Simao terrane (SMT), and 42 km in the east direction beneath Chengdu area. The crust is dominantly felsic in upper crust, with a small percentage of mafic composition in the lower crust. (2) The crustal structure is very heterogeneous in this region. The Indochina Block is characterized by low Seismic velocities in the upper crust, while the west Yangtze terrane (WYZT) and SGT show higher velocities in the upper crust. The lower crust beneath WYZT is relatively thicker than other terranes. (3) We deduce that the high velocity in the upper crust and relatively thick lower crust beneath the SGT and WYZT can be associated with magmatic processes that generated the Emeishan flood basalts which may have been triggered by rifting or mantle plume. The lateral variations of the crustal thickness in SE Tibet may be due to lower crustal flow from the Tibetan Plateau to the SE direction after blocked by the cold and rigid Yangtze craton in the east direction.
