From April, 2003 to September, 2004, a passive broadband seismic array consisting of 60 stations was deployed over the Tianshan orogenic belt by State Key Laboratory of Earthquake Dynamics, Institute of Geology, China...From April, 2003 to September, 2004, a passive broadband seismic array consisting of 60 stations was deployed over the Tianshan orogenic belt by State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration. Among them, 51 stations make up an about 500-km-long profile across the Tianshan Mountains from Kuytun to Kuqa. The receiver function profile and S-wave velocity structure of the crust and upper mantle down to 100 km deep are obtained by using the re-ceiver function method (Liu et al. 1996, 2000). The main results can be summarized as follows: (1) A clear mountain root does not exist beneath the Tianshan Mountains, and the crust-mantle boundaries underneath the stations mostly have transitional structures. This implies that the material differentia-tion between the crust and mantle is not yet accomplished and the orogenic process is still going on. (2) The crust beneath the Tianshan Mountains has laterally blocked structures in direction perpendicular to the mountain strike, and the crust-mantle boundary has a clear dislocation structure. Both of them correspond to each other. (3) The offsets of the Moho discontinuity are highly correlated to the tectonic borders on the surface and that corresponding to the frontal southern Tianshan fault reaches to 14 km. This manifests that large vertical divergent movement took place between different blocks. This sup-ports the discontinuous model of the Tianshan orogeny, and the Tarim block subduction is restricted only to the southern side of the South Tianshan. (4) Inside the upper and middle crust of the Tianshan Mountains exist several low-velocity bodies correlated with high seismicity located on the moun-tain-basin jointures on both sides of the mountain and between different blocks, and the low-velocity bodies on the mountain-basin jointures are inclined obviously to the mountain. This implies that the low-velocity bodies may be correlated closely to the thrust and subduction of the basins on both sides of the mountain, the spli展开更多
Ordos Block has undergone rapid uplift,and a series of rift basins have been formed around the block since the Cenozoic,but the formation mechanisms remain controversial.A high-resolution 3 D velocity structure of cru...Ordos Block has undergone rapid uplift,and a series of rift basins have been formed around the block since the Cenozoic,but the formation mechanisms remain controversial.A high-resolution 3 D velocity structure of crust and mantle is important for understanding the lithospheric deformation and deep dynamic process.A here we present a 3 D S-wave velocity structure of the crust and upper mantle in the Ordos Block and surrounding regions by joint inversion of receiver functions and surface wave data from a dense broadband seismic deployment.The lithosphere of the Ordos Block exhibits an obvious highvelocity anomaly.In the east and north of the Ordos and the southwestern part of the Tibetan Plateau,obvious low-velocity anomalies are detected in the upper mantle and extend into the Ordos.The lithosphere of the Ordos Block is thick in the center and thin at the edge,while the crust is relatively thin in the center and thick in the southwest and northeast.The crustal thickness of the tensional basin in the north is greater than that in the central Ordos.We suggest that the outward expansion of the mantle thermal materials in eastern Tibet and the upper mantle thermal upwelling in the eastern part of the North China Craton lead to the non-uniform lithospheric thinning,temperature rise and density reduction of the Ordos Block.The additional buoyancy and thermodynamic effects provided by them contributed to the continuous uplift of the Ordos Block since the Cenozoic.Influenced by the extrusion of Tibetan Plateau,the crustal thickening and rapid uplift occur in the southwestern and northern parts of the Ordos Block.The lithospheric structures of the Alxa and Ordos Blocks are different,and they may belong to different independent blocks before the Mesozoic.展开更多
Crustal thickness and composition are closely related to geology and tectonic evolution of the region.Studying the differences in the crustal thickness and composition of the South China Block(SCB)is important to gain...Crustal thickness and composition are closely related to geology and tectonic evolution of the region.Studying the differences in the crustal thickness and composition of the South China Block(SCB)is important to gain a comprehensive understanding of multi-phase amalgamation,breakup,reworking,and regional geodynamic processes.In this study,teleseismic data from 135 high-density portable broadband stations from Sino Probe were processed using Common Conversion Point(CCP)stacking and H-κstacking methods.The Moho depth and P-wave and S-wave velocity ratio(V_(p)/V_(s))were studied.Our results revealed several insights about the tectonic processes in the SCB.First,the crustal structure and V_(p)/V_(s)ratios of the Cathaysia Block,Jiangnan Orogenic Belt,and Yangtze Block were significantly different.The average depth of the Moho in the Cathaysia Block was approximately 31 km,and the V_(p)/V_(s)ratios increased from the inland area(1.66)to the coastal area(1.78),indicating the oceanward increase of mafic proportion in the lower crust,which is related to the influence of the Paleo-Pacific Plate westward subduction.Second,the crustal thickness of Jiangnan Orogenic Belt deepens from east ca.31 to the west ca.42 km and the V_(p)/V_(s)ratios varied from 1.75 to 1.64,illustrating a relatively felsic crust,which could have been related to the Mesozoic upper crustal thickening under compression followed by the lower crust removal under the extensional background.Third,the average crustal thickness of the Yangtze Block was 42 km,and the V_(p)/V_(s)ratios ranged from 1.64 to 1.84,presenting a positive correlation between the Moho depth and the V_(p)/V_(s)ratio,which is explained by the relatively thick mafic lower crust.Based on the variations in the crustal structure and V_(p)/V_(s)ratios of the profile,we inferred that the central part of the Jiangnan Orogenic Belt was bounded by the Jiangshan-Shaoxing-Hengyang in the east and the Jiujiang-Shitai-Jishou in the west.The small-scale Moho depth undulations at the intersection of 展开更多
A new method is developed to constrain S-wave velocity structures of the shallow crust based on frequencydependent amplitudes of direct P-waves in P-wave receiver functions(P-RFs). This method involves the following t...A new method is developed to constrain S-wave velocity structures of the shallow crust based on frequencydependent amplitudes of direct P-waves in P-wave receiver functions(P-RFs). This method involves the following two steps:first, the high-frequency approximate amplitude formula of direct P-waves in P-RFs of individual stations is used to fit the observed amplitude distribution against the ray parameters at different frequencies, and second, the S-wave velocity depth profile beneath each station is constrained according to an empirical correlation between frequency and depth. Unlike traditional inversion techniques, the newly developed method is not dependent on initial velocity models, and the lateral and vertical resolutions of the results are controlled by the interstation distance and the data frequency, respectively. The effectiveness of the method is verified by synthetic tests on various models. The method is then applied to teleseismic P-RF data from a NW-SEtrending linear seismic array extending from the northeastern Tibetan Plateau to the central Sichuan Basin to construct an S-wave velocity image of the shallow crust along the array. The imaged velocity structure is further analysed and compared with the regional geology. In particular, the structural differences of sedimentary basins in the cratonic area of the stable Sichuan Basin and tectonically active belts in northeastern Tibet are investigated. By combining our results with previous observations, the relationship between the surficial geology and deep processes in the study region is also discussed.展开更多
The Baikal rift is the most seismically active continental rift in the world and is significant for studying the dynamics of continental rifts, although its precise dynamic mechanisms remain controversial. We calculat...The Baikal rift is the most seismically active continental rift in the world and is significant for studying the dynamics of continental rifts, although its precise dynamic mechanisms remain controversial. We calculated receiver functions (1748) from Global Seismographic Network seismic stations TLY and ULN and stacked receiver functions in different bins. Here we present discontinuities at depths of 410km and 660km and thickness of the mantle transition zone (MTZ) beneath the study area. The MTZ structure shows an obvious thickening (292km) in the Baikal rift zone except for an area of limited thinning (230km), whereas it is basically normal (250km) beneath the Mongolian area, to the southeast of the Baikal rift. Combining these results with previous findings, we propose that the large-scale thickening beneath the Baikal rift zone is likely to be caused by the Mesozoic collision between the Siberian Platform and the Mongolia-North China Block or magmatic intrusion into the lower crust, which would result in crust and lithosphere thickening. Thus, the lower crust becomes eclogitized and consequently detached into the deep mantle because of negative buoyancy. The detachment not only induces asthenosphere upwelling but also accelerates mantle convection of water detached from the subducted slab, which would increase mantle melting, while both processes promote the development of the rift. Our preliminary results indicate that the detachment and the consequent hot upwelling have an important influence on the development of the Baikal rift, and a small-scale mantle upwelling indicated by the located thinning may have destroyed the lithosphere and promoted this development.展开更多
Tanlu fault zone(TLFZ)is the largest active fault zone in eastern China.It is characterized by complex tectonic evolution and multiple faults and marks the boundary between the North and South China blocks.An indepth ...Tanlu fault zone(TLFZ)is the largest active fault zone in eastern China.It is characterized by complex tectonic evolution and multiple faults and marks the boundary between the North and South China blocks.An indepth understanding of the distinct crustal structures of both parts of the TLFZ will provide valuable insights into the lithospheric and crustal thinning in eastern China,extensive magmatism since the Mesozoic,and formation mechanisms of metallogenic belts along the Yangtze River.In this study,a two-layer H-κstacking approach was adopted to estimate the thicknesses of the sediment and crystalline crust as well as the corresponding vP/vS ratios based on high-quality teleseismic P-wave receiver functions recorded by permanent and temporary stations in and around the TLFZ.The geological units in the study region were delineated,especially the crustal structures beneath extensive sedimentary basins on both sides of the TLFZ.The following conclusions can be drawn:(1)The crustal thickness in and around the TLFZ greatly varies depending on the segment.In the northern segment,the crust is relatively thin beneath the eastern part of the Songliao Basin,a broad uplift of the Moho can be observed,and the Moho descends from south to north.The crust below the central and southern segments becomes thinner from west to east.The thickness of the crust is less than 30 km toward the eastern side of the boundary between the Jiangsu and Anhui provinces,that is,significantly thinner than in other areas.In terms of the vP/vS ratios,high anomalies were detected in the central-southern segments of the TLFZ,indicating the upwelling of deep mantle magma via deep faults.(2)Positive isostatic gravity anomalies were observed in the eastern part of the northern segment of the TLFZ and in the eastern part of the Suwan segment.The crustal thickness is smaller than that obtained from the Airy model of isostasy.This suggests that the lower crust in this area may have experienced intensive transformation processes,which may be related to c展开更多
In this article, we analyze the characters of SV-component receiver function of teleseismic body waves and its advantages in mapping the S-wave velocity structure of crust in detail. Similar to radial receiver functio...In this article, we analyze the characters of SV-component receiver function of teleseismic body waves and its advantages in mapping the S-wave velocity structure of crust in detail. Similar to radial receiver function, SV-component receiver function can be obtained by directly deconvolving the P-component from the SV-component of teleseismic recordings. Our analyses indicate that the change of amplitude of SV-component receiver function against the change of epicentral distance is less than that of radial receiver function. Moreover, the waveform of SV-component receiver function is simpler than the radial receiver function and gives prominence to the PS converted phases that are the most sensitive to the shear wave velocity structure in the inversion. The synthetic tests show that the convergence of SV-component receiver function inversion is faster than that of the radial receiver function inversion. As an example, we investigate the S-wave velocity structure beneath HIA sta-tion by using the SV-component receiver function inversion method.展开更多
s Western Yunnan is located at the boundary of collision or underthrusting zone of Eurasian plate and is influenced by many times tectonic movements. With very complex geological environment and tectonic background, i...s Western Yunnan is located at the boundary of collision or underthrusting zone of Eurasian plate and is influenced by many times tectonic movements. With very complex geological environment and tectonic background, it is one of the seismically active areas. In the paper, the teleseismic records were selected from 16 national, local and mo-bile stations, including 4 very-wide-band mobile stations of PASSCAL. And nearly 2 000 receiver functions were extracted. Two measuring lines are 650 km and 450 km, respectively and across some major tectonic units in Western Yunnan. It is indicated that Nujiang might be a seam characterized by underthrusting. The western and eastern boundaries of Sichuan-Yunnan rhombus block, i.e., Honghe and Xiaojiang faults, might be an erection seam or collision belt. Panxi tectonic zone still has the characteristics of continental rift valley, that is, the surface is hollow and the upper mantle is upwarping. The tectonic situation in Western Yunnan is of certain regulation with the interlacing distribution of orogenic zone and seam. The crustal thickness decreases gradually from the north to the south and the S wave velocity is globally lower here.展开更多
基金the National Natural Science Foundation of China (Grant No.40234043)
文摘From April, 2003 to September, 2004, a passive broadband seismic array consisting of 60 stations was deployed over the Tianshan orogenic belt by State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration. Among them, 51 stations make up an about 500-km-long profile across the Tianshan Mountains from Kuytun to Kuqa. The receiver function profile and S-wave velocity structure of the crust and upper mantle down to 100 km deep are obtained by using the re-ceiver function method (Liu et al. 1996, 2000). The main results can be summarized as follows: (1) A clear mountain root does not exist beneath the Tianshan Mountains, and the crust-mantle boundaries underneath the stations mostly have transitional structures. This implies that the material differentia-tion between the crust and mantle is not yet accomplished and the orogenic process is still going on. (2) The crust beneath the Tianshan Mountains has laterally blocked structures in direction perpendicular to the mountain strike, and the crust-mantle boundary has a clear dislocation structure. Both of them correspond to each other. (3) The offsets of the Moho discontinuity are highly correlated to the tectonic borders on the surface and that corresponding to the frontal southern Tianshan fault reaches to 14 km. This manifests that large vertical divergent movement took place between different blocks. This sup-ports the discontinuous model of the Tianshan orogeny, and the Tarim block subduction is restricted only to the southern side of the South Tianshan. (4) Inside the upper and middle crust of the Tianshan Mountains exist several low-velocity bodies correlated with high seismicity located on the moun-tain-basin jointures on both sides of the mountain and between different blocks, and the low-velocity bodies on the mountain-basin jointures are inclined obviously to the mountain. This implies that the low-velocity bodies may be correlated closely to the thrust and subduction of the basins on both sides of the mountain, the spli
基金supported by the National Natural Science Foundation of China(Grant Nos.41774102,41804062 and 41804057)the Special Funds for Basic Scientific Research Business Fees of Institute of Geophysics,China Earthquake Administration(Grant Nos.DQJB20K41,DQJB16A03)。
文摘Ordos Block has undergone rapid uplift,and a series of rift basins have been formed around the block since the Cenozoic,but the formation mechanisms remain controversial.A high-resolution 3 D velocity structure of crust and mantle is important for understanding the lithospheric deformation and deep dynamic process.A here we present a 3 D S-wave velocity structure of the crust and upper mantle in the Ordos Block and surrounding regions by joint inversion of receiver functions and surface wave data from a dense broadband seismic deployment.The lithosphere of the Ordos Block exhibits an obvious highvelocity anomaly.In the east and north of the Ordos and the southwestern part of the Tibetan Plateau,obvious low-velocity anomalies are detected in the upper mantle and extend into the Ordos.The lithosphere of the Ordos Block is thick in the center and thin at the edge,while the crust is relatively thin in the center and thick in the southwest and northeast.The crustal thickness of the tensional basin in the north is greater than that in the central Ordos.We suggest that the outward expansion of the mantle thermal materials in eastern Tibet and the upper mantle thermal upwelling in the eastern part of the North China Craton lead to the non-uniform lithospheric thinning,temperature rise and density reduction of the Ordos Block.The additional buoyancy and thermodynamic effects provided by them contributed to the continuous uplift of the Ordos Block since the Cenozoic.Influenced by the extrusion of Tibetan Plateau,the crustal thickening and rapid uplift occur in the southwestern and northern parts of the Ordos Block.The lithospheric structures of the Alxa and Ordos Blocks are different,and they may belong to different independent blocks before the Mesozoic.
基金supported by the National Natural Science Foundation of China(Grant Nos.41630320,92062108)the China Geological Survey Project(Grant No.DD20190012)open fund from the Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resource,Institute of Geology,Chinese Academy of Geological Sciences(Grant No.J1901-16)。
文摘Crustal thickness and composition are closely related to geology and tectonic evolution of the region.Studying the differences in the crustal thickness and composition of the South China Block(SCB)is important to gain a comprehensive understanding of multi-phase amalgamation,breakup,reworking,and regional geodynamic processes.In this study,teleseismic data from 135 high-density portable broadband stations from Sino Probe were processed using Common Conversion Point(CCP)stacking and H-κstacking methods.The Moho depth and P-wave and S-wave velocity ratio(V_(p)/V_(s))were studied.Our results revealed several insights about the tectonic processes in the SCB.First,the crustal structure and V_(p)/V_(s)ratios of the Cathaysia Block,Jiangnan Orogenic Belt,and Yangtze Block were significantly different.The average depth of the Moho in the Cathaysia Block was approximately 31 km,and the V_(p)/V_(s)ratios increased from the inland area(1.66)to the coastal area(1.78),indicating the oceanward increase of mafic proportion in the lower crust,which is related to the influence of the Paleo-Pacific Plate westward subduction.Second,the crustal thickness of Jiangnan Orogenic Belt deepens from east ca.31 to the west ca.42 km and the V_(p)/V_(s)ratios varied from 1.75 to 1.64,illustrating a relatively felsic crust,which could have been related to the Mesozoic upper crustal thickening under compression followed by the lower crust removal under the extensional background.Third,the average crustal thickness of the Yangtze Block was 42 km,and the V_(p)/V_(s)ratios ranged from 1.64 to 1.84,presenting a positive correlation between the Moho depth and the V_(p)/V_(s)ratio,which is explained by the relatively thick mafic lower crust.Based on the variations in the crustal structure and V_(p)/V_(s)ratios of the profile,we inferred that the central part of the Jiangnan Orogenic Belt was bounded by the Jiangshan-Shaoxing-Hengyang in the east and the Jiujiang-Shitai-Jishou in the west.The small-scale Moho depth undulations at the intersection of
基金supported by the National Natural Science Foundation of China (Grant No. 41688103)the Strategic Priority Research Program (A) of the Chinese Academy of Sciences (Grant No. XDA20070302)+1 种基金the Independent Project of the State Key Laboratory of the Lithospheric Evolution, IGGCAS (SKL-Z201704-11712180)The field work for seismic data collection was financially supported by the Projects (Grant Nos. SinoProbe-02-03, 2011ZX05008-001)
文摘A new method is developed to constrain S-wave velocity structures of the shallow crust based on frequencydependent amplitudes of direct P-waves in P-wave receiver functions(P-RFs). This method involves the following two steps:first, the high-frequency approximate amplitude formula of direct P-waves in P-RFs of individual stations is used to fit the observed amplitude distribution against the ray parameters at different frequencies, and second, the S-wave velocity depth profile beneath each station is constrained according to an empirical correlation between frequency and depth. Unlike traditional inversion techniques, the newly developed method is not dependent on initial velocity models, and the lateral and vertical resolutions of the results are controlled by the interstation distance and the data frequency, respectively. The effectiveness of the method is verified by synthetic tests on various models. The method is then applied to teleseismic P-RF data from a NW-SEtrending linear seismic array extending from the northeastern Tibetan Plateau to the central Sichuan Basin to construct an S-wave velocity image of the shallow crust along the array. The imaged velocity structure is further analysed and compared with the regional geology. In particular, the structural differences of sedimentary basins in the cratonic area of the stable Sichuan Basin and tectonically active belts in northeastern Tibet are investigated. By combining our results with previous observations, the relationship between the surficial geology and deep processes in the study region is also discussed.
基金supported by National Natural Science Foundation of China(Grant Nos. 40974025 and 40721003)Innovative Research Group Science Foundation (Grant No. 41021063)National Key Project (Grant No.2008ZX05008-006)
文摘The Baikal rift is the most seismically active continental rift in the world and is significant for studying the dynamics of continental rifts, although its precise dynamic mechanisms remain controversial. We calculated receiver functions (1748) from Global Seismographic Network seismic stations TLY and ULN and stacked receiver functions in different bins. Here we present discontinuities at depths of 410km and 660km and thickness of the mantle transition zone (MTZ) beneath the study area. The MTZ structure shows an obvious thickening (292km) in the Baikal rift zone except for an area of limited thinning (230km), whereas it is basically normal (250km) beneath the Mongolian area, to the southeast of the Baikal rift. Combining these results with previous findings, we propose that the large-scale thickening beneath the Baikal rift zone is likely to be caused by the Mesozoic collision between the Siberian Platform and the Mongolia-North China Block or magmatic intrusion into the lower crust, which would result in crust and lithosphere thickening. Thus, the lower crust becomes eclogitized and consequently detached into the deep mantle because of negative buoyancy. The detachment not only induces asthenosphere upwelling but also accelerates mantle convection of water detached from the subducted slab, which would increase mantle melting, while both processes promote the development of the rift. Our preliminary results indicate that the detachment and the consequent hot upwelling have an important influence on the development of the Baikal rift, and a small-scale mantle upwelling indicated by the located thinning may have destroyed the lithosphere and promoted this development.
文摘Tanlu fault zone(TLFZ)is the largest active fault zone in eastern China.It is characterized by complex tectonic evolution and multiple faults and marks the boundary between the North and South China blocks.An indepth understanding of the distinct crustal structures of both parts of the TLFZ will provide valuable insights into the lithospheric and crustal thinning in eastern China,extensive magmatism since the Mesozoic,and formation mechanisms of metallogenic belts along the Yangtze River.In this study,a two-layer H-κstacking approach was adopted to estimate the thicknesses of the sediment and crystalline crust as well as the corresponding vP/vS ratios based on high-quality teleseismic P-wave receiver functions recorded by permanent and temporary stations in and around the TLFZ.The geological units in the study region were delineated,especially the crustal structures beneath extensive sedimentary basins on both sides of the TLFZ.The following conclusions can be drawn:(1)The crustal thickness in and around the TLFZ greatly varies depending on the segment.In the northern segment,the crust is relatively thin beneath the eastern part of the Songliao Basin,a broad uplift of the Moho can be observed,and the Moho descends from south to north.The crust below the central and southern segments becomes thinner from west to east.The thickness of the crust is less than 30 km toward the eastern side of the boundary between the Jiangsu and Anhui provinces,that is,significantly thinner than in other areas.In terms of the vP/vS ratios,high anomalies were detected in the central-southern segments of the TLFZ,indicating the upwelling of deep mantle magma via deep faults.(2)Positive isostatic gravity anomalies were observed in the eastern part of the northern segment of the TLFZ and in the eastern part of the Suwan segment.The crustal thickness is smaller than that obtained from the Airy model of isostasy.This suggests that the lower crust in this area may have experienced intensive transformation processes,which may be related to c
基金State Key Basic Research Development and Programming Project (G199804070201) State Natural Science Foundation (40074008).
文摘In this article, we analyze the characters of SV-component receiver function of teleseismic body waves and its advantages in mapping the S-wave velocity structure of crust in detail. Similar to radial receiver function, SV-component receiver function can be obtained by directly deconvolving the P-component from the SV-component of teleseismic recordings. Our analyses indicate that the change of amplitude of SV-component receiver function against the change of epicentral distance is less than that of radial receiver function. Moreover, the waveform of SV-component receiver function is simpler than the radial receiver function and gives prominence to the PS converted phases that are the most sensitive to the shear wave velocity structure in the inversion. The synthetic tests show that the convergence of SV-component receiver function inversion is faster than that of the radial receiver function inversion. As an example, we investigate the S-wave velocity structure beneath HIA sta-tion by using the SV-component receiver function inversion method.
文摘s Western Yunnan is located at the boundary of collision or underthrusting zone of Eurasian plate and is influenced by many times tectonic movements. With very complex geological environment and tectonic background, it is one of the seismically active areas. In the paper, the teleseismic records were selected from 16 national, local and mo-bile stations, including 4 very-wide-band mobile stations of PASSCAL. And nearly 2 000 receiver functions were extracted. Two measuring lines are 650 km and 450 km, respectively and across some major tectonic units in Western Yunnan. It is indicated that Nujiang might be a seam characterized by underthrusting. The western and eastern boundaries of Sichuan-Yunnan rhombus block, i.e., Honghe and Xiaojiang faults, might be an erection seam or collision belt. Panxi tectonic zone still has the characteristics of continental rift valley, that is, the surface is hollow and the upper mantle is upwarping. The tectonic situation in Western Yunnan is of certain regulation with the interlacing distribution of orogenic zone and seam. The crustal thickness decreases gradually from the north to the south and the S wave velocity is globally lower here.
