The Red Sea-Gulf of Suez-Cairo-Alexandria Clysmic-Trend in northern Egypt is the main earthquake zone in the country,with a moderate-to-high seismic hazard and a history of significant earthquakes caused by rifting an...The Red Sea-Gulf of Suez-Cairo-Alexandria Clysmic-Trend in northern Egypt is the main earthquake zone in the country,with a moderate-to-high seismic hazard and a history of significant earthquakes caused by rifting and active faulting.To improve our understanding of the tectonic and seismic processes in this area,more comprehensive imaging of the crustal structure is required.This can be achieved by increasing the number of receiver functions(RFs)recorded by the seismic stations in northern Egypt and the southeastern Mediterranean.Data handling and processing should also be automated to increase process efficiency.In this study,we developed a capsule neural network for automated selection of RFs.The model was trained on a dataset containing RFs(both selected and unselected)from five broadband stations in northern Egypt.Stations SLM,SIWA,KOT,NBNS,and NKL are located in the unstable shelf region of Egypt,where limited knowledge of the deep crustal structure is available.The proposed capsule neural network achieved an average precision of 80%on the test set.The automated selection of RFs using a capsule neural network has the potential to significantly improve the efficiency and accuracy of RF analysis,as demonstrated by the stacking test.This could lead to a better understanding of crustal structure and tectonic processes in northern Egypt and the southeastern Mediterranean.展开更多
Lithospheric structure beneath the northeastern Qinghai-Xizang Plateau is of vital significance for studying the geodynamic processes of crustal thickening and expansion of the Qinghai-Xizang Plateau. We conducted a j...Lithospheric structure beneath the northeastern Qinghai-Xizang Plateau is of vital significance for studying the geodynamic processes of crustal thickening and expansion of the Qinghai-Xizang Plateau. We conducted a joint inversion of receiver functions and surface wave dispersions with P-wave velocity constraints using data from the Chin Array Ⅱ temporary stations deployed across the Qinghai-Xizang Plateau. Prior to joint inversion, we applied the H-κ-c method(Li JT et al., 2019) to the receiver function data in order to correct for the back-azimuthal variations in the arrival times of Ps phases and crustal multiples caused by crustal anisotropy and dipping interfaces. High-resolution images of vS, crustal thickness, and vP/vSstructures in the Qinghai-Xizang Plateau were simultaneously derived from the joint inversion. The seismic images reveal that crustal thickness decreases outward from the Qinghai-Xizang Plateau. The stable interiors of the Ordos and Alxa blocks exhibited higher velocities and lower crustal vP/vSratios. While, lower velocities and higher vP/vSratios were observed beneath the Qilian Orogen and Songpan-Ganzi terrane(SPGZ), which are geologically active and mechanically weak, especially in the mid-lower crust.Delamination or thermal erosion of the lithosphere triggered by hot asthenospheric flow contributes to the observed uppermost mantle low-velocity zones(LVZs) in the SPGZ. The crustal thickness, vS, and vP/vSratios suggest that whole lithospheric shortening is a plausible mechanism for crustal thickening in the Qinghai-Xizang Plateau, supporting the idea of coupled lithospheric-scale deformation in this region.展开更多
We collected high-quality teleseismic events recorded by 12 broadband seismographs deployed in the Anyuan Coal Mine and its adjacent areas in Pingxiang City,Jiangxi Province for nearly two years.The H-κ-c stacking me...We collected high-quality teleseismic events recorded by 12 broadband seismographs deployed in the Anyuan Coal Mine and its adjacent areas in Pingxiang City,Jiangxi Province for nearly two years.The H-κ-c stacking method was employed to obtain the crustal thickness and Poisson's ratio distribution,then the characteristics of crustal structure below the stations were obtained by using the time-domain linear inversion method.The crustal thickness in the Anyuan Coal Mine and its adjacent areas ranges from approximately 32~35 km,with an average thickness of 33 km,which is consistent with the crustal thickness results in South China from previous studies using the receiver function method.The average Poisson's ratio of the crustal bulk composition in the study area varies between 0.22 and 0.25,which is lower than the global value with a 0.27 average,indicating a predominantly intermediate-acidic or felsic crustal composition.There is a weak negative correlation between Poisson's ratio and crustal thickness estimates in the Anyuan Coal Mine and its adjacent areas,suggesting that the absence of mafic-ultramafic materials in the lower crust is associated with the process of crustal delamination.The velocity inversion results indicate that the crustal structure including three velocity discontinuity interfaces,with the first at a depth of approximately 1.5 km,the second at about 10~15 km,and the third being the Moho.The study also indicates that the results obtained by the H-κ-c stacking method are significantly better than those obtained by the H-κmethod,effectively reducing the standard deviation and dispersion of crustal thickness and vP/vSratio.展开更多
Using the seismic records of 83 temporary and 17 permanent broadband seismic stations deployed in Tangshan earthquake region and its adjacent areas(39°N–41.5°N,115.5°E–119.5°E),we conducted a non...Using the seismic records of 83 temporary and 17 permanent broadband seismic stations deployed in Tangshan earthquake region and its adjacent areas(39°N–41.5°N,115.5°E–119.5°E),we conducted a nonlinear joint inversion of receiver functions and surface wave dispersion.We obtained some detailed information about the Tangshan earthquake region and its adjacent areas,including sedimentary thickness,Moho depth,and crustal and upper mantle S-wave velocity.Meanwhile,we also obtained the vP/vS structure along two sections across the Tangshan region.The results show that:(1)the Moho depth ranges from 30 km to 38 km,and it becomes shallower from Yanshan uplift area to North China basin;(2)the thickness of sedimentary layer ranges from 0 km to 3 km,and it thickens from Yanshan uplift region to North China basin;(3)the S-wave velocity structure shows that the velocity distribution of the upper crust has obvious correlation with the surface geological structure,while the velocity characteristics of the middle and lower crust are opposite to that of the upper crust.Compared with the upper crust,the heterogeneity of the middle and lower crust is more obvious;(4)the discontinuity of Moho on the two sides of Tangshan fault suggests that Tangshan fault cut the whole crust,and the low vS and high vP/vS beneath the Tangshan earthquake region may reflect the invasion of mantle thermal material through Tangshan fault.展开更多
We analyzed a total of 37 427 receiver-function data recorded by national and regional broadband seismic networks of the China Earthquake Administration to study the mantle transition zone beneath eastern and central ...We analyzed a total of 37 427 receiver-function data recorded by national and regional broadband seismic networks of the China Earthquake Administration to study the mantle transition zone beneath eastern and central China. Significant topography on both the 410-km and 660-km discontinuities was clearly imaged in the 3D volume of CCP （common-conversion-point） stacked images that cover an area of 102.5°F-122.5°E and 22.0°N-42.0°N. 3D crustal and mantle velocity models were used in computing the Ps time moveouts to better image the absolute depths of the two discontinuities. We found that the 660-km discontinuity is depressed up to 25 km along the east coast of China, indicating the presence of the subducted Pacific slab in the region. More interestingly, a double 660-km was observed beneath the Huanghai Sea, which was not seen from the 410-km discontinuity. We found a strong and localized anomaly beneath the Quaternary Datong volcano located at the northeastern edge of the Ordos Plateau in North China. The 410-km is depressed by as much as 15 km beneath the volcano. If the amount of the depression is caused by unmodeled low velocity anomaly in the upper mantle, it requires either a strong （4%-8%） localized low velocity anomaly near the lithosphere-asthenosphere boundary or -1.5% low velocity column across the entire upper mantle above the 410-km. The latter could suggest a deep origin of the Datong volcano, although it was usually attributed to edge-driven convection by most of the literatures.展开更多
The Binchuan region is located in a seismically active area in northwestern Yunnan,China.The detailed crustal structure is important to understand the tectonic evolution and to assess the seismic hazard in the study a...The Binchuan region is located in a seismically active area in northwestern Yunnan,China.The detailed crustal structure is important to understand the tectonic evolution and to assess the seismic hazard in the study area.With a 2-D dense array deployed in this region,we use teleseismic receiver function traditional imaging methods,including the H-κand common-conversion-point stacking methods,to derive high-resolution crustal thickness and vP/vS ratio maps.Our results indicate that the crustal thickness increases from~40 km to~46 km in the south-north direction,and the average crustal thickness beneath the Binchuan basin is~42 km.Our results agree with previous results but have higher resolution due to dense interstation spacing.展开更多
The Tian Shan is a vast range that spans several countries in Asia.Understanding its evolutionary history may provide valuable insights into intracontinental orogenic dynamics.In this study,we explored the crustal cha...The Tian Shan is a vast range that spans several countries in Asia.Understanding its evolutionary history may provide valuable insights into intracontinental orogenic dynamics.In this study,we explored the crustal characteristics of the Tian Shan and their relationships to the tectonic evolution of the region.A new H-stacking method that combines the P receiver function and gravity anomalies was used to estimate the thickness and ratio of P-to S-wave velocities(Vp/Vs)for 91 broadband seismic stations in the central and western Tian Shan.Our results revealed significant lateral variations in crustal thickness and Vp/Vs.A—45-km-thick crust and an intermediate-high Vp/Vs(-1.74-1.84)were found in the Kazakh Shield and Tarim Basin,which we interpreted to indicate a mafic crystalline basement and lower crust.The central Tian Shan varied greatly in crustal thickness(40-64 km)and Vp/Vs ratio(1.65-2.00).which may be due to crustal shortening,mafic underplating,and crustal melting.In contrast,we observed a relatively thin crust(42-50 km)with an intermediate Vp/Vs ratio(-1.78)in the western Tian Shan.The differences in the crustal structures between the western and central Tian Shan imply that the Talas-Fergana Fault may be trans-lithospheric.展开更多
Yunnan Province is located on the southeastern margin of Tibet and represents an important marker in understanding the tectonic evolution of Tibetan Plateau. In this study, we calculated teleseismic P-wave receiver fu...Yunnan Province is located on the southeastern margin of Tibet and represents an important marker in understanding the tectonic evolution of Tibetan Plateau. In this study, we calculated teleseismic P-wave receiver functions at 49 permanent broadband seismic stations in Yunnan Province and estimated crustal thickness and the bulk crust ratios of P-wave to S-wave velocities using the H-κ method together with more detailed crustal structural profiles from the common conversion point stacking method. There is a significant transition of Moho interface and lower crustal composition along latitude 26°N in northwestern Yunnan. Decrease of crustal thickness with a concomitant increase of Poisson’s ratio occurs at station CUX. An interesting phenomenon is that a step-like Moho fashion is observed at several stations, which might correspond to local thermal activities, such as partial melt/lower crust delamination. Our results show changes in crustal properties appear to be associated with varieties in upper mantle structure and compositions. We propose the controlling factor of the dynamic processes below 26°N is the result of eastern forward subduction of the Indian Plate; the northern part is controlled by the redirected material flow from the SE Tibet.展开更多
The teleseismic receiver functions of digital seismic network of Ningxia and its adjacent area are calculated with two different Gauss filter factors. The accuracy and stability of the receiver functions are discussed...The teleseismic receiver functions of digital seismic network of Ningxia and its adjacent area are calculated with two different Gauss filter factors. The accuracy and stability of the receiver functions are discussed. The h-k stacking method is applied to estimate the crustal thickness and velocity ratio beneath seismic stations. The results indicate that there are sharp changes of crustal thickness and velocity ratio in the studied region. This region is located in the northeastern margin of Tibet, and also a junction of several first-grade blocks. The large contrast of crustal structure in this region is considered to be resulted from the interaction of these blocks. Our results are helpful to construct the completed model of the formation and evolution of the Tibet. Some local structures are also discussed combining with the geological faults.展开更多
The teleseismic receiver functions of 48 stations belonging to the CCDSN are used to invert the crustal structure beneath each station with the neighborhood algorithm. Thin layers with low velocity have been found ben...The teleseismic receiver functions of 48 stations belonging to the CCDSN are used to invert the crustal structure beneath each station with the neighborhood algorithm. Thin layers with low velocity have been found beneath eight stations with ＂abnormal＂ observed receiver functions. Unreasonable results of few stations have been adjusted lightly with the trial-and-error method. The final result indicates that the crust in the western China is relatively thicker than the eastern China. The crust thickness beneath the Tibetan plateau is very large, which reaches 84 km at the station LSA. Double-crust structure exists below the stations LSA and CAD in Tibet, which might imply the collision between the Indian and Eurasian plates. A pronounced low velocity zone in the lower crust beneath the station TNC of Yunnan province might relate to the high temperature or emergence of partially molten material caused by Quaternary volcano, magma and geothermal activities in this area. The Moho is a transitional zone made up of thin layers instead of simple sharp discontinuity beneath several stations. The Conrad discontinuity is clearly identified beneath 20 stations mainly in the southeastern China, whereas it is blurry beneath 14 stations and uncertain beneath remaining stations.展开更多
The crustal thicknesses and the Poisson’s ratios under the seismic stations can be calculated by receiver function method with H-κ stacking effectively. But the stacking results are affected to some extent by the av...The crustal thicknesses and the Poisson’s ratios under the seismic stations can be calculated by receiver function method with H-κ stacking effectively. But the stacking results are affected to some extent by the average crustal P-wave velocity. To eliminate this effect and get more accurate crustal structure along the Zhenkang-Luxi deep seismic sounding profile which lies in Yunnan Province, we calculate the receiver functions from the teleseismic events recorded by 11 temporary stations as well as 5 permanent ones along the profile and carry out the stacking with Vp obtained from the profile in this study. Our study shows that the crustal thicknesses along the Zhenkang-Luxi profile range from 34.8 km to 41.8 km with an average of 39 km. The crust is thicker in the middle part of the profile and thinner in both sides in general. Dramatic changes of crustal thickness about 3 km are detected across both the Lancangjiang fault and the Xiaojiang fault, which implies that these faults cut through the Moho. The lowest Poisson’s ratio under the stations is 0.22 and the highest is 0.27 with the mean of 0.25, which is lower than the global average value 0.27 in the continental crust. It suggests that most of the crust along the profile lacks mafic component, but contains more felsic substance. The low Poisson’s ratio also indicates that there is no satisfying condition for partial melting. We deduce that the material flow in the middle-lower crust in the southeastern margin of the Tibetan plateau may occur only in the north region of 24°N.展开更多
We conducted comprehensive receiver function analyses for a large amount of high-quality broadband teleseismic waveforms data recorded at 19 China National Digital Seismic Network （CNDSN） stations deployed in Northe...We conducted comprehensive receiver function analyses for a large amount of high-quality broadband teleseismic waveforms data recorded at 19 China National Digital Seismic Network （CNDSN） stations deployed in Northeast China. An advanced H-κ domain search method was adopted to accurately estimate the crustal thickness and vp/vs ratio. The crust has an average thickness of about 34.4 km. The thinnest crust occurs in the central region of Northeast China, while the thickest crust is beneath the Yanshan belt. The vp/vs ratio is relatively uniform with an average of about 1.733. The highest vp/vs ratio is found beneath the Changbaishan, likely associated with its volcanic activities. We found significant lateral heterogeneity beneath three stations CN2, MDJ, and MIH located along the Suolon suture from the back-zimuthal dependence of Moho depth. The velocity modeling from receiver functions indicated complicated Earth structure beneath these stations with large crust-mantle transition zone, noticeable velocity jump in upper mantle, and low velocity zone in middle crust. Dipping velocity interface in the crust with strike approximately parallel to the Suolon suture and down-dip to the south or southeast might explain the observed lateral heterogeneity.展开更多
The P receiver function includes P-to-SV converted phases and multiple reverberations of the discontinuities in the crust and mantle.The time of these phases is related to the crustal thickness and vp/vs ratio,and the...The P receiver function includes P-to-SV converted phases and multiple reverberations of the discontinuities in the crust and mantle.The time of these phases is related to the crustal thickness and vp/vs ratio,and the amplitude of these phases is mainly controlled by the velocity and density contrast of interfaces.By using H-κstacking method,this work estimated the crustal thickness and vP/vS ratio beneath the stations in the Guangdong province of South China.The velocity and density contrast(δβ-δρ)scanning stacking algorithm of the receiver function is applied to constrain the velocity and density contrast of the Moho in Guangdong province.This work analyzed the results of the crustal thickness,vp/vS ratio,and the velocity and density contrasts of Moho.The results indicate that the velocity contrast is higher beneath Yangjiang area in western Guangdong province and Nanao area in eastern Guangdong,which has a strong correlation with the distribution of geothermal springs in local areas and the characteristics of high heat flow.The velocity contrast of Moho has also a good correlation with the vP/vS ratio and the crustal thickness,which indicates that there is a strong material composition contrasts of the Moho in the study area.Velocity and density contrasts of Moho in some local area(such as western Guangdong)are somewhat consistent with the seismic activities.展开更多
A peeling linear inversion method is presented to study the upper mantle （from Moho to 800 km depth） velocity structures with receiver functions. The influences of the crustal and upper mantle velocity ratio error o...A peeling linear inversion method is presented to study the upper mantle （from Moho to 800 km depth） velocity structures with receiver functions. The influences of the crustal and upper mantle velocity ratio error on the inversion results are analyzed, and three valid measures are taken for its reduction. This method is tested with the IASP91 and the PREM models, and the upper mantle structures beneath the stations GTA, LZH, and AXX in northwestern China are then inverted. The results indicate that this inversion method is feasible to quantify upper mantle discontinuities, besides the discontinuities between 3hM （hM denotes the depth of Moho） and 5hM due to the interference of multiples from Moho. Smoothing is used to overcome possible false discontinuities from the multiples and ensure the stability of the inversion results, but the detailed information on the depth range between 3hM and 5hM is sacrificed.展开更多
Based on the observational data from 60 short-period stations deployed in the Jishishan M6.2 earthquake epicenter and adjacent regions(Gansu Province,2023),this study inverted the near-surface S-wave velocity structur...Based on the observational data from 60 short-period stations deployed in the Jishishan M6.2 earthquake epicenter and adjacent regions(Gansu Province,2023),this study inverted the near-surface S-wave velocity structure through teleseismic receiver function analysis by using the amplitude of direct P-wave.The results reveal that the epicentral area(Liugou Township and surroundings)exhibits markedly low S-wave velocities of 400-600 m/s,with a mean value of(500±50)m/s.In contrast,intermountain basins-Guanting Basin and Dahejia Basin-demonstrate significantly elevated velocities,exceeding the epicentral zone by 100-300 m/s,with values concentrated at 600-900 m/s.Notably,localized areas such as Jintian Village and Caotan Village maintain stable S-wave velocities of(700±30)m/s.The western margin tectonic belt of Jishishan displays distinctive velocity differentiation:A pronounced velocity gradient zone along the 35.8°N latitude boundary separates northern areas(<550 m/s)from southern regions(>750 m/s).These findings demonstrate significant spatial heterogeneity in shallow S-wave velocity structures,primarily controlled by three factors:(1)topographic-geomorphic units,(2)stratigraphic lithological contrasts,and(3)anthropogenic modifications.The persistent low-velocity anomalies(<600 m/s)in the epicentral zone and northern Yellow River T2 terrace likely correlate with Quaternary unconsolidated sediments,enhanced groundwater circulation,and bedrock weathering.These results provide critical geophysical constraints for understanding both the seismogenic environment of the Jishishan earthquake and its damage distribution patterns.Furthermore,they establish a foundational framework for regional seismic intensity evaluation,site amplification analysis,and secondary hazard risk assessment.展开更多
During Mesozoic to Cenozoic time, the large-scale tectono-magmatism had strongly modified the lithosphere beneath the southeastern continent of China, leaving the present-day lithosphere as a new one evolving from the...During Mesozoic to Cenozoic time, the large-scale tectono-magmatism had strongly modified the lithosphere beneath the southeastern continent of China, leaving the present-day lithosphere as a new one evolving from the ancient lithosphere that was largely removed and replaced. But this model proposed from geochemical and petrological research is urgently in need of support from seismic observational evidence. In this paper, based on the dataset recorded by the dense stations of two NE ori- ented broadband seismic profiles deployed in the coastal area of southeastern China （SE China）, both P-wave （P-RF） and S-wave （S-RF） receiver functions were isolated. We identified Pls phase converted from the Lithosphere-Asthenosphere Boundary （LAB） in P-RFs of individual stations. Migrated Pls phase indicated a depth of 60-70 km for LAB. Inver- sions/comparisons of P-RF （Pls phase） and S-RF （Sip phase） waveforms together with Ps and Sp imaging for the crust and up- per mantle structure further confirmed this result. P-RF and S-RF migrated images exhibit that a flat LAB is positioned at the depth of 60-70 km spreading along the profile, whereas a distinct structural change of lithospheric base appears at the Min River estuary. Both Ps and PpPs migrated images of P-RFs present an abrupt Moho drop across the Min River fault from south to north, which is consistent with previous result obtained from deep seismic sounding. By taking into consideration other ge- ological and geophysical features such as locally high anomalies of crustal Poisson＇s ratios and heat flow at the Min River es- tuary, we infer that the Min River fault penetrates down to the Moho and may, furthermore, interfere in the deeper lithospheric structure.展开更多
The North China Craton(NCC) is an important part of eastern China. Recent studies have shown that the eastern NCC(ENCC) has undergone significant lithospheric thinning and destruction since the late Mesozoic. Destruct...The North China Craton(NCC) is an important part of eastern China. Recent studies have shown that the eastern NCC(ENCC) has undergone significant lithospheric thinning and destruction since the late Mesozoic. Destruction of the cratonic lithosphere is necessarily accompanied by crustal deformation. Therefore, a detailed crustal deformation model can provide basic observational constraints for understanding the process and mechanisms of the destruction of the NCC. In this study, we estimated the crustal azimuthal anisotropy beneath 198 broadband stations in the NCC with a joint analysis of Ps waves converted at the Moho from radial and transverse receiver function data. We also performed a harmonic analysis to test the reliability of the measured anisotropy. We obtained robust crustal azimuthal anisotropy beneath 23 stations that are mostly located on the western margin of the Bohai Bay Basin, Yin-Yan orogenic belt, and Taihang Mountains, which reflects the crustal deformation characteristics in those regions. The crustal shear wave splitting time was found to range from 0.05 s to 0.68 s, with an average value of 0.23 s, which reveals a distinct crustal anisotropy in the Trans-North China Orogen(TNCO) and its adjacent areas. Our analysis of the results suggests that the strong NW-SE tectonic extension in the late Mesozoic and Cenozoic played an important role in crustal anisotropy in this region. In addition, the E-W trending crustal anisotropy on the margin of the Bohai Bay Basin indicates an effect of the ENE-WSW trending horizontal principal compressive stress. The crustal anisotropy in the Yin-Yan orogenic belt may be an imprint of the multiple-phase shortening of a dominant N-S direction from the early-to-middle Jurassic to the Early Cretaceous. Stations in the Taihang Mountains show large splitting times and well-aligned NW-SE fast directions that correlate with those measured from SKS splitting and that are possibly related to the lithospheric modification and magmatic underplating from the Late Mesozoic to Cenozoic in this area.展开更多
We use 15 seismic stations, crossing the Qinling orogen （QO）, Weihe graben （WG） and Ordos block （OB）, to study the crustal structures by receiver functions （RFs） methods. The results show quite a difference in...We use 15 seismic stations, crossing the Qinling orogen （QO）, Weihe graben （WG） and Ordos block （OB）, to study the crustal structures by receiver functions （RFs） methods. The results show quite a difference in crustal structures and materials of three tectonic units （orogenic belt, extentional basin and stable craton）. The average crustal thickness in the northern QO is 37.8 km, and Poisson ratio is 0.247, which indicates the increase of felsic materials in QO. In the southern OB, the average crustal thickness is 39.2 km and Poisson ratio is 0.265. Comparatively high value of Poisson ratio is related with old crystallized base in the lower crust and shallow sediments. The artificial RFs reveal that low-velocity and thick sediments have a significant ef fect on phases of the MohoroviEi6 discontinuity （Moho）. As a result, the Moho phases in WG are tangled. S-wave velocity （Vs） inversion shows that there are shallow sediment layers with 4-8 km＇s thickness and high velocity zones in the middle-lower crust in WG. Complex Moho structure and high velocity zone may have been induced by the activities of the Weihe faults series.展开更多
Landslides are recurrent geological phenomena on Earth that cause heavy casualties and property losses annually.In this study,we use the V_(p)-k stacking and nonlinear waveform inversion methods of high-frequency rece...Landslides are recurrent geological phenomena on Earth that cause heavy casualties and property losses annually.In this study,we use the V_(p)-k stacking and nonlinear waveform inversion methods of high-frequency receiver functions extracted from local earthquakes,to sequentially invert Poisson’s ratios and S-wave velocities of the Quaternary Xishancun landslide,which is composed of three segments,i.e.,h1,h2,and h3 from bottom to top.Our results show that Poisson’s ratio values are generally higher than 0.33 and that the S-wave velocities vary from 0.1 to 0.9 km s^(-1).High Poisson’s ratios(>0.44)are mainly distributed in the juncture regions between different segments,as well as the western edge of h2.These zones show significant variation in landslide thickness and are potentially hazardous areas.Low velocities of 0.05–0.2 km s^(-1)with thicknesses of 10–30m are widely observed in the lower layer of the landslide.The high Poisson’s ratios and low-velocity layer may be related to water-rich materials in these areas.Our study suggests that the high-frequency receiver functions from local earthquakes can be used to delineate geotechnical structures,which is valuable for landslide stability analysis and hazard mitigation.展开更多
In this study,high-resolution Moho depth and average crustal V_(p)/V_(s) ratio distributions in northeast China were obtained through joint inversion of receiver functions and gravity data.The new joint inversion meth...In this study,high-resolution Moho depth and average crustal V_(p)/V_(s) ratio distributions in northeast China were obtained through joint inversion of receiver functions and gravity data.The new joint inversion method comprehensively considers the complementary imaging strengths of the receiver functions in the vertical direction and the gravity data in the lateral direction.To a certain extent,it can reduce the adverse effects of the receiver function data caused by the sedimentary layers of the basin,the inclination of the Moho,and the structure heterogeneity below the station.In preprocessing the receiver function data,a regularized virtual station network was constructed using the teleseismic receiver function waveform reconstruction method to improve the overall spatial resolution.To filter the gravity data,the velocity structure-guided gravity filtering method and gravity upward continuation were used for the shallower region above the Moho and the deeper region below the lithosphere,respectively.The newly obtained model shows that the Moho depths of the Hailar Basin,Erlian Basin,Sanjiang Basin,and Bohai Bay Basin are slightly shallower than those of the surrounding areas,while the Moho depths of the Greater Xing’an Range,Lesser Xing’an Range,and Zhangguangcai Range are slightly deeper.Compared with previous results,the refined Moho depth distribution obtained in this study has a better correspondence with topographic relief and basin boundaries,and the contrast is more evident across the north-south gravity gradient lineament(NSGL).In the eastern part of the Songliao Basin,the Moho is relatively shallow,and there is a high V_(p)/V_(s) ratio,which may have been caused by the intrusion of hot mantle materials into the crust induced by lateral extension of the Songliao Basin.The high V_(p)/V_(s) ratio of the crust below the Changbaishan volcanic area implies the existence of partial melting in the crust caused by upwelling hot mantle materials.展开更多
文摘The Red Sea-Gulf of Suez-Cairo-Alexandria Clysmic-Trend in northern Egypt is the main earthquake zone in the country,with a moderate-to-high seismic hazard and a history of significant earthquakes caused by rifting and active faulting.To improve our understanding of the tectonic and seismic processes in this area,more comprehensive imaging of the crustal structure is required.This can be achieved by increasing the number of receiver functions(RFs)recorded by the seismic stations in northern Egypt and the southeastern Mediterranean.Data handling and processing should also be automated to increase process efficiency.In this study,we developed a capsule neural network for automated selection of RFs.The model was trained on a dataset containing RFs(both selected and unselected)from five broadband stations in northern Egypt.Stations SLM,SIWA,KOT,NBNS,and NKL are located in the unstable shelf region of Egypt,where limited knowledge of the deep crustal structure is available.The proposed capsule neural network achieved an average precision of 80%on the test set.The automated selection of RFs using a capsule neural network has the potential to significantly improve the efficiency and accuracy of RF analysis,as demonstrated by the stacking test.This could lead to a better understanding of crustal structure and tectonic processes in northern Egypt and the southeastern Mediterranean.
基金supported by the Natural Science Basic Research Program of Shaanxi(No.2023-JC-QN-0306)the Special Fund of the Institute of Geophysics,China Earthquake Administration(No.DQJB21B32)the National Natural Science Foundation of China(No.42174069).
文摘Lithospheric structure beneath the northeastern Qinghai-Xizang Plateau is of vital significance for studying the geodynamic processes of crustal thickening and expansion of the Qinghai-Xizang Plateau. We conducted a joint inversion of receiver functions and surface wave dispersions with P-wave velocity constraints using data from the Chin Array Ⅱ temporary stations deployed across the Qinghai-Xizang Plateau. Prior to joint inversion, we applied the H-κ-c method(Li JT et al., 2019) to the receiver function data in order to correct for the back-azimuthal variations in the arrival times of Ps phases and crustal multiples caused by crustal anisotropy and dipping interfaces. High-resolution images of vS, crustal thickness, and vP/vSstructures in the Qinghai-Xizang Plateau were simultaneously derived from the joint inversion. The seismic images reveal that crustal thickness decreases outward from the Qinghai-Xizang Plateau. The stable interiors of the Ordos and Alxa blocks exhibited higher velocities and lower crustal vP/vSratios. While, lower velocities and higher vP/vSratios were observed beneath the Qilian Orogen and Songpan-Ganzi terrane(SPGZ), which are geologically active and mechanically weak, especially in the mid-lower crust.Delamination or thermal erosion of the lithosphere triggered by hot asthenospheric flow contributes to the observed uppermost mantle low-velocity zones(LVZs) in the SPGZ. The crustal thickness, vS, and vP/vSratios suggest that whole lithospheric shortening is a plausible mechanism for crustal thickening in the Qinghai-Xizang Plateau, supporting the idea of coupled lithospheric-scale deformation in this region.
基金supported by the Spark Program of Earthquake Technology of CEA,China(XH20032)open Research Project from the State Key Laboratory of Nuclear Resources and Environment,East China University of Technology(2022NRE17)+1 种基金open Research Project from the State Key Laboratory of Geological Processes,Mineral Resources,China University of Geosciences(GPMR202114)the Graduate Student Innovation Fund of East China University of Technology(YC2022-s628)。
文摘We collected high-quality teleseismic events recorded by 12 broadband seismographs deployed in the Anyuan Coal Mine and its adjacent areas in Pingxiang City,Jiangxi Province for nearly two years.The H-κ-c stacking method was employed to obtain the crustal thickness and Poisson's ratio distribution,then the characteristics of crustal structure below the stations were obtained by using the time-domain linear inversion method.The crustal thickness in the Anyuan Coal Mine and its adjacent areas ranges from approximately 32~35 km,with an average thickness of 33 km,which is consistent with the crustal thickness results in South China from previous studies using the receiver function method.The average Poisson's ratio of the crustal bulk composition in the study area varies between 0.22 and 0.25,which is lower than the global value with a 0.27 average,indicating a predominantly intermediate-acidic or felsic crustal composition.There is a weak negative correlation between Poisson's ratio and crustal thickness estimates in the Anyuan Coal Mine and its adjacent areas,suggesting that the absence of mafic-ultramafic materials in the lower crust is associated with the process of crustal delamination.The velocity inversion results indicate that the crustal structure including three velocity discontinuity interfaces,with the first at a depth of approximately 1.5 km,the second at about 10~15 km,and the third being the Moho.The study also indicates that the results obtained by the H-κ-c stacking method are significantly better than those obtained by the H-κmethod,effectively reducing the standard deviation and dispersion of crustal thickness and vP/vSratio.
基金This research is supported by Spark Program of Earthquake Science(No.XH18065Y)National Natural Science Foundation of China(Nos.41774066 and 41604049)。
文摘Using the seismic records of 83 temporary and 17 permanent broadband seismic stations deployed in Tangshan earthquake region and its adjacent areas(39°N–41.5°N,115.5°E–119.5°E),we conducted a nonlinear joint inversion of receiver functions and surface wave dispersion.We obtained some detailed information about the Tangshan earthquake region and its adjacent areas,including sedimentary thickness,Moho depth,and crustal and upper mantle S-wave velocity.Meanwhile,we also obtained the vP/vS structure along two sections across the Tangshan region.The results show that:(1)the Moho depth ranges from 30 km to 38 km,and it becomes shallower from Yanshan uplift area to North China basin;(2)the thickness of sedimentary layer ranges from 0 km to 3 km,and it thickens from Yanshan uplift region to North China basin;(3)the S-wave velocity structure shows that the velocity distribution of the upper crust has obvious correlation with the surface geological structure,while the velocity characteristics of the middle and lower crust are opposite to that of the upper crust.Compared with the upper crust,the heterogeneity of the middle and lower crust is more obvious;(4)the discontinuity of Moho on the two sides of Tangshan fault suggests that Tangshan fault cut the whole crust,and the low vS and high vP/vS beneath the Tangshan earthquake region may reflect the invasion of mantle thermal material through Tangshan fault.
文摘We analyzed a total of 37 427 receiver-function data recorded by national and regional broadband seismic networks of the China Earthquake Administration to study the mantle transition zone beneath eastern and central China. Significant topography on both the 410-km and 660-km discontinuities was clearly imaged in the 3D volume of CCP （common-conversion-point） stacked images that cover an area of 102.5°F-122.5°E and 22.0°N-42.0°N. 3D crustal and mantle velocity models were used in computing the Ps time moveouts to better image the absolute depths of the two discontinuities. We found that the 660-km discontinuity is depressed up to 25 km along the east coast of China, indicating the presence of the subducted Pacific slab in the region. More interestingly, a double 660-km was observed beneath the Huanghai Sea, which was not seen from the 410-km discontinuity. We found a strong and localized anomaly beneath the Quaternary Datong volcano located at the northeastern edge of the Ordos Plateau in North China. The 410-km is depressed by as much as 15 km beneath the volcano. If the amount of the depression is caused by unmodeled low velocity anomaly in the upper mantle, it requires either a strong （4%-8%） localized low velocity anomaly near the lithosphere-asthenosphere boundary or -1.5% low velocity column across the entire upper mantle above the 410-km. The latter could suggest a deep origin of the Datong volcano, although it was usually attributed to edge-driven convection by most of the literatures.
基金supported by the National Key R&D Program of China(No.2018YFC1503400)China Earthquake Science Experiment Project,CEA(Nos.2018CSES0101,2018CSES0102 and 2019CSES0107)+2 种基金HKSAR Research Grant Council GRF(No.14305617)CUHK Direct Grant from Faculty of Science,National Natural Scientific Foundation of China(Nos.41974069 and 41790463)Chen Yong Academician Workstation of Yunnan Province in China(No.2014IC007)。
文摘The Binchuan region is located in a seismically active area in northwestern Yunnan,China.The detailed crustal structure is important to understand the tectonic evolution and to assess the seismic hazard in the study area.With a 2-D dense array deployed in this region,we use teleseismic receiver function traditional imaging methods,including the H-κand common-conversion-point stacking methods,to derive high-resolution crustal thickness and vP/vS ratio maps.Our results indicate that the crustal thickness increases from~40 km to~46 km in the south-north direction,and the average crustal thickness beneath the Binchuan basin is~42 km.Our results agree with previous results but have higher resolution due to dense interstation spacing.
基金supported by the National Science Foundation of China (Nos. U1839210, 41874097, 41474072, and 41874108)
文摘The Tian Shan is a vast range that spans several countries in Asia.Understanding its evolutionary history may provide valuable insights into intracontinental orogenic dynamics.In this study,we explored the crustal characteristics of the Tian Shan and their relationships to the tectonic evolution of the region.A new H-stacking method that combines the P receiver function and gravity anomalies was used to estimate the thickness and ratio of P-to S-wave velocities(Vp/Vs)for 91 broadband seismic stations in the central and western Tian Shan.Our results revealed significant lateral variations in crustal thickness and Vp/Vs.A—45-km-thick crust and an intermediate-high Vp/Vs(-1.74-1.84)were found in the Kazakh Shield and Tarim Basin,which we interpreted to indicate a mafic crystalline basement and lower crust.The central Tian Shan varied greatly in crustal thickness(40-64 km)and Vp/Vs ratio(1.65-2.00).which may be due to crustal shortening,mafic underplating,and crustal melting.In contrast,we observed a relatively thin crust(42-50 km)with an intermediate Vp/Vs ratio(-1.78)in the western Tian Shan.The differences in the crustal structures between the western and central Tian Shan imply that the Talas-Fergana Fault may be trans-lithospheric.
基金supported by the 973 Project of China(No.2013CB733303)the National Natural Science Foundation of China(No.41474093)
文摘Yunnan Province is located on the southeastern margin of Tibet and represents an important marker in understanding the tectonic evolution of Tibetan Plateau. In this study, we calculated teleseismic P-wave receiver functions at 49 permanent broadband seismic stations in Yunnan Province and estimated crustal thickness and the bulk crust ratios of P-wave to S-wave velocities using the H-κ method together with more detailed crustal structural profiles from the common conversion point stacking method. There is a significant transition of Moho interface and lower crustal composition along latitude 26°N in northwestern Yunnan. Decrease of crustal thickness with a concomitant increase of Poisson’s ratio occurs at station CUX. An interesting phenomenon is that a step-like Moho fashion is observed at several stations, which might correspond to local thermal activities, such as partial melt/lower crust delamination. Our results show changes in crustal properties appear to be associated with varieties in upper mantle structure and compositions. We propose the controlling factor of the dynamic processes below 26°N is the result of eastern forward subduction of the Indian Plate; the northern part is controlled by the redirected material flow from the SE Tibet.
基金supported by the basic research and development fund from Institute of Earthquake Science,China Earthquake Administration(grant No.2011IESLZ05)the National Natural Science Foundation of China(grant No.40904014)
文摘The teleseismic receiver functions of digital seismic network of Ningxia and its adjacent area are calculated with two different Gauss filter factors. The accuracy and stability of the receiver functions are discussed. The h-k stacking method is applied to estimate the crustal thickness and velocity ratio beneath seismic stations. The results indicate that there are sharp changes of crustal thickness and velocity ratio in the studied region. This region is located in the northeastern margin of Tibet, and also a junction of several first-grade blocks. The large contrast of crustal structure in this region is considered to be resulted from the interaction of these blocks. Our results are helpful to construct the completed model of the formation and evolution of the Tibet. Some local structures are also discussed combining with the geological faults.
基金supported by the basic research and development fund from Institute of Earthquake Science,China Earthquake Administration(grant No.2011IESLZ05)the National Natural Science Foundation of China(grant Nos.40374009and 40904014)
文摘The teleseismic receiver functions of 48 stations belonging to the CCDSN are used to invert the crustal structure beneath each station with the neighborhood algorithm. Thin layers with low velocity have been found beneath eight stations with ＂abnormal＂ observed receiver functions. Unreasonable results of few stations have been adjusted lightly with the trial-and-error method. The final result indicates that the crust in the western China is relatively thicker than the eastern China. The crust thickness beneath the Tibetan plateau is very large, which reaches 84 km at the station LSA. Double-crust structure exists below the stations LSA and CAD in Tibet, which might imply the collision between the Indian and Eurasian plates. A pronounced low velocity zone in the lower crust beneath the station TNC of Yunnan province might relate to the high temperature or emergence of partially molten material caused by Quaternary volcano, magma and geothermal activities in this area. The Moho is a transitional zone made up of thin layers instead of simple sharp discontinuity beneath several stations. The Conrad discontinuity is clearly identified beneath 20 stations mainly in the southeastern China, whereas it is blurry beneath 14 stations and uncertain beneath remaining stations.
基金supported by the Seismic Youth Funding of Geophysical Exploration Center,China Earthquake Administration (YFGEC2016003)the National Natural Science Foundation of China (41774070 and 41404049)
文摘The crustal thicknesses and the Poisson’s ratios under the seismic stations can be calculated by receiver function method with H-κ stacking effectively. But the stacking results are affected to some extent by the average crustal P-wave velocity. To eliminate this effect and get more accurate crustal structure along the Zhenkang-Luxi deep seismic sounding profile which lies in Yunnan Province, we calculate the receiver functions from the teleseismic events recorded by 11 temporary stations as well as 5 permanent ones along the profile and carry out the stacking with Vp obtained from the profile in this study. Our study shows that the crustal thicknesses along the Zhenkang-Luxi profile range from 34.8 km to 41.8 km with an average of 39 km. The crust is thicker in the middle part of the profile and thinner in both sides in general. Dramatic changes of crustal thickness about 3 km are detected across both the Lancangjiang fault and the Xiaojiang fault, which implies that these faults cut through the Moho. The lowest Poisson’s ratio under the stations is 0.22 and the highest is 0.27 with the mean of 0.25, which is lower than the global average value 0.27 in the continental crust. It suggests that most of the crust along the profile lacks mafic component, but contains more felsic substance. The low Poisson’s ratio also indicates that there is no satisfying condition for partial melting. We deduce that the material flow in the middle-lower crust in the southeastern margin of the Tibetan plateau may occur only in the north region of 24°N.
文摘We conducted comprehensive receiver function analyses for a large amount of high-quality broadband teleseismic waveforms data recorded at 19 China National Digital Seismic Network （CNDSN） stations deployed in Northeast China. An advanced H-κ domain search method was adopted to accurately estimate the crustal thickness and vp/vs ratio. The crust has an average thickness of about 34.4 km. The thinnest crust occurs in the central region of Northeast China, while the thickest crust is beneath the Yanshan belt. The vp/vs ratio is relatively uniform with an average of about 1.733. The highest vp/vs ratio is found beneath the Changbaishan, likely associated with its volcanic activities. We found significant lateral heterogeneity beneath three stations CN2, MDJ, and MIH located along the Suolon suture from the back-zimuthal dependence of Moho depth. The velocity modeling from receiver functions indicated complicated Earth structure beneath these stations with large crust-mantle transition zone, noticeable velocity jump in upper mantle, and low velocity zone in middle crust. Dipping velocity interface in the crust with strike approximately parallel to the Suolon suture and down-dip to the south or southeast might explain the observed lateral heterogeneity.
基金the National Key R&D Program of China(No.2017YFC1500100)National Natural Science Foundation of China(Nos.U1701641,41874052,41730211 and 41774049)+5 种基金Guangdong Province Introduced Innovative R&D Team(Nos.2017ZT07Z066 and 2016ZT06N331)Guangdong Science and Technology Plan Project(No.2017B030314082)Combination Project with Monitoring,Prediction and Scientific Research of Earthquake Technology,CEA(No.3JH-201901051)Seismic Regime Tracking Project of CEA(No.2020010111)Some figures were plotted with Generic Mapping Tools(Wessel and Smith,1995)The authors sincerely acknowledge the anonymous reviewers and journal editors for their help,support,checking and helpful comments to the manuscript.
文摘The P receiver function includes P-to-SV converted phases and multiple reverberations of the discontinuities in the crust and mantle.The time of these phases is related to the crustal thickness and vp/vs ratio,and the amplitude of these phases is mainly controlled by the velocity and density contrast of interfaces.By using H-κstacking method,this work estimated the crustal thickness and vP/vS ratio beneath the stations in the Guangdong province of South China.The velocity and density contrast(δβ-δρ)scanning stacking algorithm of the receiver function is applied to constrain the velocity and density contrast of the Moho in Guangdong province.This work analyzed the results of the crustal thickness,vp/vS ratio,and the velocity and density contrasts of Moho.The results indicate that the velocity contrast is higher beneath Yangjiang area in western Guangdong province and Nanao area in eastern Guangdong,which has a strong correlation with the distribution of geothermal springs in local areas and the characteristics of high heat flow.The velocity contrast of Moho has also a good correlation with the vP/vS ratio and the crustal thickness,which indicates that there is a strong material composition contrasts of the Moho in the study area.Velocity and density contrasts of Moho in some local area(such as western Guangdong)are somewhat consistent with the seismic activities.
基金supported by the basic research and development fund from Institute of Earthquake Science,China Earthquake Administration(grant No.2011IESLZ05)National Natural Science Foundation of China(grant Nos.40574024 and 40374009)
文摘A peeling linear inversion method is presented to study the upper mantle （from Moho to 800 km depth） velocity structures with receiver functions. The influences of the crustal and upper mantle velocity ratio error on the inversion results are analyzed, and three valid measures are taken for its reduction. This method is tested with the IASP91 and the PREM models, and the upper mantle structures beneath the stations GTA, LZH, and AXX in northwestern China are then inverted. The results indicate that this inversion method is feasible to quantify upper mantle discontinuities, besides the discontinuities between 3hM （hM denotes the depth of Moho） and 5hM due to the interference of multiples from Moho. Smoothing is used to overcome possible false discontinuities from the multiples and ensure the stability of the inversion results, but the detailed information on the depth range between 3hM and 5hM is sacrificed.
基金project is supported in part by Broadband Seismic 3D Array Detection(PhaseⅠ),Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(Grant No.2024ZD1000300)National Natural Science Foundation of China(42204061)Gansu Jishishan 6.2 magnitude earthquake scientific investigation(DQJB23Y45)program。
文摘Based on the observational data from 60 short-period stations deployed in the Jishishan M6.2 earthquake epicenter and adjacent regions(Gansu Province,2023),this study inverted the near-surface S-wave velocity structure through teleseismic receiver function analysis by using the amplitude of direct P-wave.The results reveal that the epicentral area(Liugou Township and surroundings)exhibits markedly low S-wave velocities of 400-600 m/s,with a mean value of(500±50)m/s.In contrast,intermountain basins-Guanting Basin and Dahejia Basin-demonstrate significantly elevated velocities,exceeding the epicentral zone by 100-300 m/s,with values concentrated at 600-900 m/s.Notably,localized areas such as Jintian Village and Caotan Village maintain stable S-wave velocities of(700±30)m/s.The western margin tectonic belt of Jishishan displays distinctive velocity differentiation:A pronounced velocity gradient zone along the 35.8°N latitude boundary separates northern areas(<550 m/s)from southern regions(>750 m/s).These findings demonstrate significant spatial heterogeneity in shallow S-wave velocity structures,primarily controlled by three factors:(1)topographic-geomorphic units,(2)stratigraphic lithological contrasts,and(3)anthropogenic modifications.The persistent low-velocity anomalies(<600 m/s)in the epicentral zone and northern Yellow River T2 terrace likely correlate with Quaternary unconsolidated sediments,enhanced groundwater circulation,and bedrock weathering.These results provide critical geophysical constraints for understanding both the seismogenic environment of the Jishishan earthquake and its damage distribution patterns.Furthermore,they establish a foundational framework for regional seismic intensity evaluation,site amplification analysis,and secondary hazard risk assessment.
基金supported by Sinoprobe02-03(Grant No.201011042)the National Natural Science Foundation of China(Grant No.41174081)
文摘During Mesozoic to Cenozoic time, the large-scale tectono-magmatism had strongly modified the lithosphere beneath the southeastern continent of China, leaving the present-day lithosphere as a new one evolving from the ancient lithosphere that was largely removed and replaced. But this model proposed from geochemical and petrological research is urgently in need of support from seismic observational evidence. In this paper, based on the dataset recorded by the dense stations of two NE ori- ented broadband seismic profiles deployed in the coastal area of southeastern China （SE China）, both P-wave （P-RF） and S-wave （S-RF） receiver functions were isolated. We identified Pls phase converted from the Lithosphere-Asthenosphere Boundary （LAB） in P-RFs of individual stations. Migrated Pls phase indicated a depth of 60-70 km for LAB. Inver- sions/comparisons of P-RF （Pls phase） and S-RF （Sip phase） waveforms together with Ps and Sp imaging for the crust and up- per mantle structure further confirmed this result. P-RF and S-RF migrated images exhibit that a flat LAB is positioned at the depth of 60-70 km spreading along the profile, whereas a distinct structural change of lithospheric base appears at the Min River estuary. Both Ps and PpPs migrated images of P-RFs present an abrupt Moho drop across the Min River fault from south to north, which is consistent with previous result obtained from deep seismic sounding. By taking into consideration other ge- ological and geophysical features such as locally high anomalies of crustal Poisson＇s ratios and heat flow at the Min River es- tuary, we infer that the Min River fault penetrates down to the Moho and may, furthermore, interfere in the deeper lithospheric structure.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41574034, 41688103, and 91414301)
文摘The North China Craton(NCC) is an important part of eastern China. Recent studies have shown that the eastern NCC(ENCC) has undergone significant lithospheric thinning and destruction since the late Mesozoic. Destruction of the cratonic lithosphere is necessarily accompanied by crustal deformation. Therefore, a detailed crustal deformation model can provide basic observational constraints for understanding the process and mechanisms of the destruction of the NCC. In this study, we estimated the crustal azimuthal anisotropy beneath 198 broadband stations in the NCC with a joint analysis of Ps waves converted at the Moho from radial and transverse receiver function data. We also performed a harmonic analysis to test the reliability of the measured anisotropy. We obtained robust crustal azimuthal anisotropy beneath 23 stations that are mostly located on the western margin of the Bohai Bay Basin, Yin-Yan orogenic belt, and Taihang Mountains, which reflects the crustal deformation characteristics in those regions. The crustal shear wave splitting time was found to range from 0.05 s to 0.68 s, with an average value of 0.23 s, which reveals a distinct crustal anisotropy in the Trans-North China Orogen(TNCO) and its adjacent areas. Our analysis of the results suggests that the strong NW-SE tectonic extension in the late Mesozoic and Cenozoic played an important role in crustal anisotropy in this region. In addition, the E-W trending crustal anisotropy on the margin of the Bohai Bay Basin indicates an effect of the ENE-WSW trending horizontal principal compressive stress. The crustal anisotropy in the Yin-Yan orogenic belt may be an imprint of the multiple-phase shortening of a dominant N-S direction from the early-to-middle Jurassic to the Early Cretaceous. Stations in the Taihang Mountains show large splitting times and well-aligned NW-SE fast directions that correlate with those measured from SKS splitting and that are possibly related to the lithospheric modification and magmatic underplating from the Late Mesozoic to Cenozoic in this area.
基金supported by National Natural Science Foundation of China(Grant Nos.41174038 and 40474017)
文摘We use 15 seismic stations, crossing the Qinling orogen （QO）, Weihe graben （WG） and Ordos block （OB）, to study the crustal structures by receiver functions （RFs） methods. The results show quite a difference in crustal structures and materials of three tectonic units （orogenic belt, extentional basin and stable craton）. The average crustal thickness in the northern QO is 37.8 km, and Poisson ratio is 0.247, which indicates the increase of felsic materials in QO. In the southern OB, the average crustal thickness is 39.2 km and Poisson ratio is 0.265. Comparatively high value of Poisson ratio is related with old crystallized base in the lower crust and shallow sediments. The artificial RFs reveal that low-velocity and thick sediments have a significant ef fect on phases of the MohoroviEi6 discontinuity （Moho）. As a result, the Moho phases in WG are tangled. S-wave velocity （Vs） inversion shows that there are shallow sediment layers with 4-8 km＇s thickness and high velocity zones in the middle-lower crust in WG. Complex Moho structure and high velocity zone may have been induced by the activities of the Weihe faults series.
基金supported by the Strategic Priority Research Program(B)of Chinese Academy of Sciences(Grant No.XDB41000000)the National Natural Science Foundation of China(Grant Nos.41604056,41661164035)。
文摘Landslides are recurrent geological phenomena on Earth that cause heavy casualties and property losses annually.In this study,we use the V_(p)-k stacking and nonlinear waveform inversion methods of high-frequency receiver functions extracted from local earthquakes,to sequentially invert Poisson’s ratios and S-wave velocities of the Quaternary Xishancun landslide,which is composed of three segments,i.e.,h1,h2,and h3 from bottom to top.Our results show that Poisson’s ratio values are generally higher than 0.33 and that the S-wave velocities vary from 0.1 to 0.9 km s^(-1).High Poisson’s ratios(>0.44)are mainly distributed in the juncture regions between different segments,as well as the western edge of h2.These zones show significant variation in landslide thickness and are potentially hazardous areas.Low velocities of 0.05–0.2 km s^(-1)with thicknesses of 10–30m are widely observed in the lower layer of the landslide.The high Poisson’s ratios and low-velocity layer may be related to water-rich materials in these areas.Our study suggests that the high-frequency receiver functions from local earthquakes can be used to delineate geotechnical structures,which is valuable for landslide stability analysis and hazard mitigation.
基金supported by the National Key R&D Program of China(Grant No.2022YFF0800701)the National Natural Science Foundation of China(Grant No.U1839205)。
文摘In this study,high-resolution Moho depth and average crustal V_(p)/V_(s) ratio distributions in northeast China were obtained through joint inversion of receiver functions and gravity data.The new joint inversion method comprehensively considers the complementary imaging strengths of the receiver functions in the vertical direction and the gravity data in the lateral direction.To a certain extent,it can reduce the adverse effects of the receiver function data caused by the sedimentary layers of the basin,the inclination of the Moho,and the structure heterogeneity below the station.In preprocessing the receiver function data,a regularized virtual station network was constructed using the teleseismic receiver function waveform reconstruction method to improve the overall spatial resolution.To filter the gravity data,the velocity structure-guided gravity filtering method and gravity upward continuation were used for the shallower region above the Moho and the deeper region below the lithosphere,respectively.The newly obtained model shows that the Moho depths of the Hailar Basin,Erlian Basin,Sanjiang Basin,and Bohai Bay Basin are slightly shallower than those of the surrounding areas,while the Moho depths of the Greater Xing’an Range,Lesser Xing’an Range,and Zhangguangcai Range are slightly deeper.Compared with previous results,the refined Moho depth distribution obtained in this study has a better correspondence with topographic relief and basin boundaries,and the contrast is more evident across the north-south gravity gradient lineament(NSGL).In the eastern part of the Songliao Basin,the Moho is relatively shallow,and there is a high V_(p)/V_(s) ratio,which may have been caused by the intrusion of hot mantle materials into the crust induced by lateral extension of the Songliao Basin.The high V_(p)/V_(s) ratio of the crust below the Changbaishan volcanic area implies the existence of partial melting in the crust caused by upwelling hot mantle materials.
