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
A method for reconstructing crustal velocity structure using the optimization of stacking receiver function amplitude in the depth domain,named common conversion amplitude(CCA)inversion,is presented.The conversion amp...A method for reconstructing crustal velocity structure using the optimization of stacking receiver function amplitude in the depth domain,named common conversion amplitude(CCA)inversion,is presented.The conversion amplitude in the depth domain,which represents the impedance change in the medium,is obtained by assigning the receiver function amplitude to the corresponding conversion position where the P-to-S conversion occurred.Utilizing the conversion amplitude variation with depth as an optimization objective,imposing reliable prior constraints on the structural model frame and velocity range,and adopting a stepwise search inversion technique,this method efficiently weakens the tendency of easily falling into the local extremum in conventional receiver function inversion.Synthetic tests show that the CCA inversion can reconstruct complex crustal velocity structures well and is especially suitable for revealing crustal evolution by estimating diverse velocity distributions.Its performance in reconstructing crustal structure is superior to that of the conventional receiver function imaging method.展开更多
Teleseismic events have been selected from a database of earthquakes with three components which were recorded between February 2005 and January 2007 by five seismic stations across the Garoua rift region which consti...Teleseismic events have been selected from a database of earthquakes with three components which were recorded between February 2005 and January 2007 by five seismic stations across the Garoua rift region which constitutes a part of the Cameroon Volcanic Line (CVL). The iterative time deconvolution performed by [1] applied on these teleseismic events, permitted us to obtain P-receiver functions. The latter were subsequently inverted in order to obtain S-wave velocity models with respect to depth which were then associated to the synthetic receiver functions. This made it possible to explain the behavior of the wave and the medium through which they traveled. The main results obtained indicate that: (1) The lithosphere appears to be thin in its crustal part with a mean Moho depth of 28 km and S wave velocity of 3.7 km/s. (2) In its mantle part, the lithosphere is thick in nature having a thickness that varies between 42 km and 67.2 km. The greatest depth is noticed towards the center located around Garoua while the least depth corresponds to a location around Yagoua in the North. The Low velocity zone which makes it possible to determine the depth of the lithosphere was seen to have a thickness which varies between 42 km and 118.8 km. (3) The synthetic receiver functions associated to shear velocity models reveal that, on one hand the wave has really undergone a conversion and multiple conversions such that the existing Ps phase and subsequent reverberations PpPs and PpSs have mean times of 3.7 s, 11 s and 17.6 s respectively. On the other hand, they reveal an attenuation shown by the decrease in the amplitude of the aforementioned phases along a South-North direction in the Garoua rift.展开更多
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.
基金financially supported by the National Natural Science Foundation of China(Grant 91755214).
文摘A method for reconstructing crustal velocity structure using the optimization of stacking receiver function amplitude in the depth domain,named common conversion amplitude(CCA)inversion,is presented.The conversion amplitude in the depth domain,which represents the impedance change in the medium,is obtained by assigning the receiver function amplitude to the corresponding conversion position where the P-to-S conversion occurred.Utilizing the conversion amplitude variation with depth as an optimization objective,imposing reliable prior constraints on the structural model frame and velocity range,and adopting a stepwise search inversion technique,this method efficiently weakens the tendency of easily falling into the local extremum in conventional receiver function inversion.Synthetic tests show that the CCA inversion can reconstruct complex crustal velocity structures well and is especially suitable for revealing crustal evolution by estimating diverse velocity distributions.Its performance in reconstructing crustal structure is superior to that of the conventional receiver function imaging method.
文摘Teleseismic events have been selected from a database of earthquakes with three components which were recorded between February 2005 and January 2007 by five seismic stations across the Garoua rift region which constitutes a part of the Cameroon Volcanic Line (CVL). The iterative time deconvolution performed by [1] applied on these teleseismic events, permitted us to obtain P-receiver functions. The latter were subsequently inverted in order to obtain S-wave velocity models with respect to depth which were then associated to the synthetic receiver functions. This made it possible to explain the behavior of the wave and the medium through which they traveled. The main results obtained indicate that: (1) The lithosphere appears to be thin in its crustal part with a mean Moho depth of 28 km and S wave velocity of 3.7 km/s. (2) In its mantle part, the lithosphere is thick in nature having a thickness that varies between 42 km and 67.2 km. The greatest depth is noticed towards the center located around Garoua while the least depth corresponds to a location around Yagoua in the North. The Low velocity zone which makes it possible to determine the depth of the lithosphere was seen to have a thickness which varies between 42 km and 118.8 km. (3) The synthetic receiver functions associated to shear velocity models reveal that, on one hand the wave has really undergone a conversion and multiple conversions such that the existing Ps phase and subsequent reverberations PpPs and PpSs have mean times of 3.7 s, 11 s and 17.6 s respectively. On the other hand, they reveal an attenuation shown by the decrease in the amplitude of the aforementioned phases along a South-North direction in the Garoua rift.
