To clarify the complex crust-mantle deformation mechanisms adjacent to the Eastern Himalayan Syntaxis, this study investigates the deep structure of the Sanjiang Lateral Collision Zone (SLCZ), Southeastern Tibetan Plateau, using a dense linear broadband array. We employed a receiver function classification strategy based on piercingpoint locations, integrated with surface wave joint inversion and Common-Conversion-Point (CCP) migration. Our results reveal striking lateral variations in lithospheric structure. The Lancangjiang Fault (LCJF) is associated with a Moho depth offset exceeding 10 km, suggesting it penetrates into the uppermost mantle. In contrast, the Red River Fault appears to be confined within the crust along this profile. Additionally, a prominent low-velocity anomaly is identified in the uppermost mantle west of the LCJF. We interpret this feature as a potential signature of mantle upwelling, possibly linked to regional magmatic systems, which may actively modulate overlying crustal deformation. These findings imply that deep lithospheric discontinuities and mantle dynamics, rather than crustal channel flow alone, play a dominant role in the tectonic evolution of the region.

SUMMARY The ocean is the primary source of seismic ambient noise. Therefore, seismic recordings at seafloor stations should reveal noise characteristics more directly than land stations. However, due to a lack of broad-band seismic instrumentation, seafloor noise studies using seafloor stations have been inadequate compared to land-based instrumentation. In this study, we use seismic data collected at the South China Sea (SCS) seafloor by newly developed ocean bottom seismographs (OBSs) to analyze the ambient noise features in this marginal sea. The broad-band OBS, dubbed ‘Pankun’, has unique shielding to isolate its sensor from the influences of bottom currents. A side-by-side land test between the OBS sensor unit and a standalone seismometer showed that the self-noise caused by the gimbal and the pressure case is insignificant. The recordings on the SCS seafloor have distinct noise spectra. The double frequency microseisms (DFMs) have a single instead of double peak like that seen for Pacific stations. The peak appears in a lower period range (1–5 s) than in the global noise model, indicating that the primary source region for the DFM is the SCS itself. The high-frequency content of the DFM is attenuated more as it propagates from its source region (seafloor) to land stations. The single frequency microseism (SFM) peak on the spectrum is weak, reflecting that SFMs, generated in shallow water along the coast, have difficulties propagating back into the deep ocean due to the substantial increase in seafloor depth. A long-period Earth's hum signal is also identifiable on the vertical component at periods greater than 50 s, probably due to the anti-current design of the OBS. Although the seasonal sea state mainly affects the noise level, extreme events such as typhoons can produce short-term abnormally high DFMs in the basin. However, the DFM highs caused by such events exhibit complex patterns, depending on the wind speed, duration, and area covered by the events.

计算了滇西北地区的16个固定地震台和喜马拉雅台阵项目的103个流动台站(共119个地震台站)记录的238个5.8级以上的远震事件,从中挑选了5558个信噪比高、震相清晰的接收函数,采用人工读取震相到时的方法,获得了各个台站下方的地壳厚度和泊松比.结果显示:滇西北地区地壳厚度等值线呈ES向舌状突出,地壳厚度和泊松比横向变化明显.经拟合,研究区域内地壳厚度和海拔呈正相关线性特征,深大断裂对区域构造特征和深部动力环境起控制作用.澜沧江断裂和怒江断裂北部可能是青藏高原物质向川滇侧向挤出的通道,丽江-小金河断裂深部存在流变物质.

腾冲火山区是我国著名的新生代板块内部火山活动区,壳幔物质交换比较活跃,存在着再次喷发的可能.火山喷发造成腾冲地区68座火山口以及多个火山堰塞湖、火山口湖、恪碉堪塞瀑布和139处温泉等,使其成为一个著名的旅游地区.因此,腾冲火山结构的研究具有重要的科学意义和社会价值,受到科学界和旅游界的广泛关注和研究.本文首先归纳总结了火山区地质学,大地构造学,地球化学以及地球物理学的研究成果;其次,重点剖析和讨论了地震学方法对腾冲火山区壳幔结构的研究进展以及存在的争议;然后,我们进一步整合分析了近年来不同学者在地壳结构的相关成果,以及火山区一条南北向剖面下方的S波速度和地震活动性.结果表明腾冲火山区地壳厚度主要在33.8 km到40.9 km之间,Vp/Vs比主要在1.61到1.95范围内变化.腾冲火山区95％以上地震分布在深度15 km以上,马鞍山和老鬼坡火山口下方地震占据了所有地震的80％.地震既发生在低速区,也发生在高速区,同时也发生在高低速交界处.最后我们探讨了腾冲火山区壳幔结构的研究不足,并提出了相关展望.

利用程海断裂带附近27个数字地震台站远震波形资料,提取每一个台站的接收函数,计算出各台站莫霍面深度同时利用时间域线性反演方法,获得了各个台站下方的横波速度.结果显示:程海断裂带莫霍面深度从南部42 km增至北部的54 km,南部和北部莫霍面深度有明显的不同.从程海断裂带下方不同深度S波速度剖面可以看出,宾川及其北东部地区中下地壳存在明显的低速层,此低速层可能与还没有固结的热物质有关.而永胜南部地区,地壳中S波速度垂直变化剧烈,低速异常高速异常交替丛生,这可能是此区地震频发的主要原因.同时,本文对宽频带地震仪和短周期地震仪得到的接收函数进行了初步的对比分析.

We have studied the crust and uppermost mantle S-wave velocity structure beneath Japan Islands by using the teleseismic waveform data above Mw 6.0 recorded from January 2006 to February 2017 by 15 Hi-Net stations and the joint inversion technique of P- and S-wave receiver functions based on the Bayes theory. The results show that, beneath Japan Islands, the crust appear the characteristic of thinner in the south and east, and thicker in the north and west. The thinnest and thickest crust in the study region locate at station JSD (26km) and JGF(44km), respectively. The horizontal distribution of S-wave velocity in the study region are relatively complicated within upper and middle crust depth, while from the lower crust to the uppermost mantle depth, the velocity distribution is relatively uniform. The large earthquakes (above Mw 6.0) mainly took place at the edge of the high and low velocity zones.

利用宾川主动源项目16个地震台站2011年9月～2014年1月期间记录的5.8级以上远震波形资料,提取各台站下方的P波接收函数,并据此计算、分析宾川地区地壳厚度变化情况和泊松比分布特征.高空间分辨率的结果显示:宾川地区平均地壳厚为45.3 km,地壳厚度呈“北深南浅”、“西浅东深”的特征.地壳厚度最深的是小银甸,47.9 km,最浅的是排营台,42.1 km,两者相差5.8 km.程海断裂附近Moho面较深,红河断裂附近Moho面较浅;程海断裂附近地壳厚度变化较明显,红河断裂附近变化较缓.从泊松比的分布情况来看,研究区内泊松比分布是不均匀的,自南向北存在较大差异,呈“北低南高”的特征.红河断裂附近,泊松比属于中高(0.26≤σ≤0.29),程海断裂附近,泊松比较低(σ≤0.26).泊松比分布特征和地壳厚度相反,表明宾川地区的增厚方式主要由上地壳增厚所致.

芦山地震的发震构造迄今为止仍不明确.文中基于中国地震局地震预测研究所2008-2009年间布设于龙门山断裂带南段的流动地震台站观测剖面、芦山地震余震精定位结果等地球物理资料对深部构造单元进行了分析;同时基于阶地变形资料、遥感资料、区域地质资料等手段对地表构造变形进行了分析;综合两者建立芦山地震的构造变形模式并研究芦山地震的发震构造.初步认为由于断层面倾角的差异,芦山地震的构造变形模式和中北段与汶川地震有关的主要破裂段的变形模式有所不同.南段前山断裂近直立的断层面最终以对下盘的挤压作用为主,并在下盘地块内形成逆冲断层引发了芦山地震;而北段中央断裂陡倾的断层面使得仍然以上盘的逆冲作用为主.新生逆冲断层的上盘形成了1个活动背斜,第四纪以来该活动背斜之上的阶地面已经发生了显著的变形,该断层最新的1次活动导致了芦山地震的发生.大溪乡与太平镇之间向SE方向凸出的弧形断层段长期以来已经累积了巨大的位移量或构造变形量,是应变释放、构造运动都集中发生的段.芦山地震只是这种构造模式的长期演化过程中的1次地震事件,未来南段前山断裂下盘的这些新生活动逆冲断层仍然具有发生类似地震的危险性.

利用地震背景噪声提取台站间的面波频散信息,进而进行地下结构研究是目前地球物理学的研究热点之一.本文详细介绍了该方法的发展历程,并以流动台阵和固定地震台站数据为例给出了较为详细的噪声数据处理过程,重点阐述了如何利用地震背景噪声提取瑞利面波的频散曲线.此外,对基层科研人员如何更好地应用固定台站数据资料的技术细节问题给出了具体解决方案.

The Tibetan Plateau is expanding eastwards, but the modes of deformation are poorly understood. High-resolution seismic images from the region identify localized zones of weak crustal rocks as well as deep faults, implying that deformation occurs through a combination of crustal flow and movement of rigid blocks of crust.

S-receiver function is valuable for investigating the lithosphere velocity structure.Using synthetic seismogram technique,we have studied dynamic characteristics of S-receiver functions.Based on the Bayesian inversion theory and non-linear inversion technique of the complex spectral ratio of the P-receiver function,a joint P-and S-receiver function inversion technique is proposed in this study.Our results show that(1) epicenter distances are limited to 55°~80° for the S-receiver function inversion and the magnitude of events used in the inversion should be larger than 5.0 for a good enough signal to noise ratio;(2) the SLP conversion on the lithosphere-asthenosphere boundary(LAB) with gradient structure is weaker than that on the sharp LAB,and the sediment is in favor of the SLP conversion at LAB;(3) since the radial component of S-receiver functions is not a delta pulse,the multi-channel maximal likelihood deconvolution technique for three-component receiver function estimation not relying on the source equalization assumption is more suitable for estimating S-receiver function;(4) numerical tests demonstrate that when the deviation of initial model is within 20% from the true model,our method can well predict the model parameters of the crust and upper mantle down to 300 km depth;(5) observational data tests demonstrate that the resultant S-wave velocities at depth larger than 100 km are less well constrained.

From the broadband data recorded by the digital seismic network of Jiangsu Province in 2011,this paper selected two station groups Aand B(each has four stations).The two groups were under different ambient noise area and the average station distances were 44.6km and 30.5km,respectively.Firstly,by the sliding window cross-correlation technique,the offsets of the Green's function were measured by ambient noise cross correlation between station-pairs in the year 2011.Then,the singular value decomposition was applied to solve the over-determined equation ofΔDS i-S j and the coefficient matrices,so as to calculate clock errorΔSi for a single station.And the covariance matrix was introduced to estimate the error range of calculation results under different confidence level.The results showed that ignoring the obvious clock error(>3s),the average RMS of time errors for eight stations was about 0.421 5s,and on the 95%confidence level,the errors ranges for the two groups of stations were±0.454 4s and ±0.428 3,respectively.The average travel time residual was about 0.386s by adopting HYPOSAT to locate actual earthquakes in Jiangsu region during the period of 2010—2011.Therefore,both residuals are consistent in accuracy,suggesting it is reliable to estimate the time error for a single station based on Green's function by noise cross-correlation.

A temporal seismic array consisted of 297 broadband seismographs was deployed in Western Sichuan(100°～105°E,26°～32°N) in 2006,and the observation covered the great 2008 Wenchuan earthquake.We used the continuous three-component ambient noise data from January,2007 to October,2008,recorded at the 137 stations north of 29°N,to study the crust seismic velocity changes before and after the earthquake.For every single station,three autocorrelation functions(ACF) and three cross correlation functions(CCF) are calculated and stacked in 10 days for three components of noise data respectively.Then we estimated the relative velocity changes by measuring travel time shifts between the 50-day-moving-average stacks and the reference empirical correlation functions.We obtained the characteristic of spatial distribution of relative velocity changes caused by Wenchuan earthquake.Our results indicate that ACF analysis can get similar coseismic velocity changes pattern with the CCF method,and the distribution of coseismic velocity changes is closely correlated with the volumetric strain changes during the Wenchuan earthquake.We also found an area of velocity increase in the region where the Longmenshan Fault zone adjoins the Xianshuihe Fault zone.This area is consistent with the faults that the Coulomb stress increased by the occurrence of the Wenchuan earthquake as predicted by the source mechanism and surface deformation.We also found that the crustal velocity increase lasted for about 2 months and then decreased with ubiquitous stress release in the studying region.

A temporal seismic array consisted of 297 broadband seismographs was deployed in Western Sichuan (100 degrees similar to 105 degrees E, 26 degrees similar to 32 degrees N) in 2006, and the observation covered the great 2008 Wenchuan earthquake. We used the continuous three-component ambient noise data from January, 2007 to October, 2008, recorded at the 137 stations north of 29 degrees N, to study the crust seismic velocity changes before and after the earthquake. For every single station, three autocorrelation functions (ACF) and three cross correlation functions (CCF) are calculated and stacked in 10 days for three components of noise data respectively. Then we estimated the relative velocity changes by measuring travel time shifts between the 50-day-moving-average stacks and the reference empirical correlation functions. We obtained the characteristic of spatial distribution of relative velocity changes caused by Wenchuan earthquake. Our results indicate that ACF analysis can get similar coseismic velocity changes pattern with the CCF method, and the distribution of coseismic velocity changes is closely correlated with the volumetric strain changes during the Wenchuan earthquake. We also found an area of velocity increase in the region where the Longmenshan Fault zone adjoins the Xianshuihe Fault zone. This area is consistent with the faults that the Coulomb stress increased by the occurrence of the Wenchuan earthquake as predicted by the source mechanism and surface deformation. We also found that the crustal velocity increase lasted for about 2 months and then decreased with ubiquitous stress release in the studying region.

In this study, we present a method for the joint inversion of receiver function and ambient noise based on Bayesian inverse theory (Tarantola, 1987, 2005) In our method, the nonlinear inversion method of the complex spectrum ratio of receiver functions (Liu et al, 1996) has been extended to perform the joint inversion of the receiver function and ambient noise with global scanning of the crustal Poisson's ratio The forward problem of the Rayleigh-wave phase dispersion is solved in terms of a modified version of the fast generalized R/T method proposed by Pei et al (2008, 2009) Our numerical tests show that (1) the dependency of inversion results on initial models has been removed and the model's parameter is estimated reliably even in the case of using a vertically homogeneous model as the initial guess for the crust structure, (2) since the consistency of the frequency band of the receiver function with the phase dispersion obtained from ambient noise is much better than that with seismic surface waves, the S-wave velocity structure in depth of 0 similar to 80 km can be well estimated in terms of the Joint inversion of receiver function and ambient noise for the phase velocity dispersion in the period of 2 similar to 40 s, and the space resolution of the shallow structure nearby the surface can reach to 1 km, (3) global scanning of the Poisson's ratio is not only in favor of data interpretation of the receiver function and ambient noise, but also provides a reliable estimation of the crustal Poisson's ratio The joint inversion of receiver function and ambient noise recorded at Station KWC05 of the western Sichuan seismic array shows that the crustal thickness beneath the station reaches to 44 km and the crustal S-wave velocity structure manifests the high-speed upper crust and low-speed middle-lower crust in depth of 24 similar to 42 km The Poisson's ratio averaged over the crust is 0 262 and that over the low-velocity zone is 0 27

A transportable array with 297 broadband seismic stations was deployed in the western Sichuan (26 degrees N similar to 32 degrees N, 100 degrees E similar to 105 degrees E) in 2006 by the State Key Laboratory of Earthquake Dynamics,Institute of Geology, China Earthquake Administration. From the ambient noise data recorded at 156 stations of this array to the north of 29 degrees N from January to December of 2007, we have obtained the surface wave empirical Green's functions (EGF) using cross-correlation technique and measured the Rayleigh-wave phase velocity dispersion curves for all possible station pairs. These dispersion measurements were then used to invert for phase velocity maps of Rayleigh waves between periods 2 similar to 35 s. Our results manifest the significant discrepancies between the crustal structures of the Chuandian block, Songpan-Garze block and Sichuan basin, which can be summarized as follows. (1) The phase velocity maps at the short periods (2 similar to 8 s) are well-correlated with the surface geological feature, and the upper crust structures of the Chuandian block,Songpan-Garze block and Sichuan basin are well confined by the Longmen Shan faults and Xianshuihe faults, especially in the foreland of the Sichuan basin, where the significant low-velocity structure suggests that a thick sediment does exist; (2) The phase velocity maps at the intermediate periods (12 similar to 18 s) manifest that the middle and lower crust velocity structure of the Chuandian and Songpan-Garze block has apparent lateral heterogeneities, including low-velocity zones of different sizes, and the upper and middle crust beneath the Sichuan basin shows high velocity structure; (3) The phase velocity maps at the long periods (25 similar to 35 s) manifest that the Songpan-Garze block and Chuandian block have an evident low-velocity anomaly in the middle-lower crust,suggesting that the middle-lower crust of these two blocks is relatively weak, and the middle-lower crust of Sichuan basin has high-velocity anomaly, suggesting a mechanically strong middle-lower crust in the basin. In particular, the crustal velocity structure along the Longmen Shan faults has a high-velocity anomaly to the north and a low-velocity anomaly to the south of the hypocenter of the Wenchuan earthquake.

In this study we use the nonlinear inversion method of receiver functions to investigate the S-wave velocity structure of the crust and upper mantle beneath the capital circle region from teleselsmic broadband waveform data recorded at 40 movable stations deployed over the Tangshan earthquake region in 2002 similar to 2003 by the Laboratory of Lithospheric Seismic Array, Institute of Geology, China Earthquake Administration and recorded at 33 permanent stations of the Digital Seismic Network in the Capital Circle. Based on these results, combining the S-wave velocity structures of the crust and upper mantle beneath 15 moveable broadband seismic stations over the Yanhual basin by Liu et al. (1997), we present the S-wave velocity distribution along the profiles with different azimuths and horizontal distributions at different depths over the region of 39 degrees similar to 41 degrees N and 114 degrees similar to 119.5 degrees E. Our results show the crustal velocity structure with spatial resolution higher than former studies due to using the data recorded by permanent and movable stations simultaneously. Our results show: (1) the S-wave velocity structure of the crust and upper mantle down to 60 km deep beneath our research area, especially to the east of the Yanhual basin, is quite complicated. The crust at depth of 10 similar to 20 km has an interlaced structure of alternating high- and low-velocity anomalies. The upper and middle crust is dominated by the NE-direction high-velocity anomalous region parallel with the Zhangjiakou-Bohai seismic zone as well as the belt across the Tangshan earthquake region, while the lower crust is dominated by the uplift of the upper mantle beneath the Yanhuai, Sanhe and Tangshan region. (2) beneath our research region exist several S-wave low velocity bodies in the crust, which are mainly distributed in the Tangshan, Sanhe, Yanhuai region, accompanied by the uplift of the crust-mantle boundary and lateral variations of the upper mantle velocity structure. (3) the fault system on the surface is well correlated with the crustal velocity structure, suggesting that the different crustal blocks are dominated by the faults. Among them, the Baodi fault, Xianghe fault, and Tangshan fault are through the crust. (4) large earthquakes in the capital circle region are related closely to the low velocity bodies in the crust and the velocity structure at the top of the upper mantle. As for the genesis of the Tangshan earthquake, it will not be sufficient only considering the horizontal stress field caused by the plate tectonics and it becomes also important to pay much attention to the vertical crustal deformation caused by the upper mantle uplift as well as the thermal effects caused by the upper mantle material intrusion.

On 12th of May, 20081 a devastating M(S)8.0 event shocking the global world occurred in the Wenchuan region of Sichuan province. Historically, the same kind of earthquakes is very rare inside of the continent. The study on the tectonic environment of this event is crucial for understanding its genesis. From the teleseismic waveform data recorded by the dense large-scale movable seismic array in the western Sichuan by the State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration (CEA), we investigate the S-wave velocity structure of the crust and upper mantle within the depth range of 120 km and averaged Poisson's ratio over the crust beneath 19 stations distributed along the profile of 31 degrees N by using the non-linear receiver function inversion technique. This profile is about 420 km long and crosses the main shock area.Our results show the differences of the crustal structure among the blocks of Chuandian Songpan-Garze and Sichuan basin. Their main features can be summarized as follows: (1) the crust-mantle boundary in the foreland of the Sichuan basin declines westward and has been deformed obviously; The crustal thickness has lateral variations of 46 similar to 52 km; the velocity of middle and lower crust has lateral variations; the Poisson's ratio averaged over the crust reaches up to 0.28 similar to 0.31; however. the crust is hard nearby the Longmen Shan faults, where the Poisson's ratio averaged over the crust is only 0.2; (2) In the Songpan-Garze block. from the West to the east, the crustal thickness becomes thinner from 60 km to 52 km; in the depth range of 14 similar to 50 km exists a wedged low-velocity zone with the S-wave velocity of 2.75 similar to 3.15 km/s, se thickness decreases from similar to 30 km in the western side to similar to 15 km in the eastern side; the whose Poisson's ratio averaged over the crust containing the low-velocity zone reaches up to 0.29 similar to 0.31; (3)the crustal structure of the Chuandian block looks simple to the west of the XianShuibe faults and the crustal thickness reaches to 58 km; but a high-velocity layer with thickness of similar to 10 km exists in the depth of 26 km; the Poisson's ratio averaged over the crust is similar to 0.25; (4) within the crust beneath the Wenchuan earthquake region exists a high-velocity structure of similar to 4.0 km/s at the depth of 12 similar to 23 km. and below it exists a low-velocity structure. where the Poisson's ratio aged over the crust is 0.31 similar to 0.32; the aftershocks of the Wenchuan earthquake are mainly aver, distributed in the region of the upper crust with high-velocity structure.Our results manifest that the Songpan-Garze block has a soft and weakened crust. and the westward subduction of the Sichuan basin does not exist. It could be inferred that under the long-term pressure eastward from the Tibetan plateau, the Songpan-Garze block obstructed by the Sichuan basin has been deformed greatly and a large energy of deformation has been accumulated inside before the Wenchuan earthquake and that the upper crust decoupled with the lower crust at the top boundary of the low-velocity zone leads to the listric thrust of the upper crust. The rigid upper crust with high-velocity underneath the Wenchuan earthquake and its adjacent region as well as the obstruction of the Sichuan basin make it possible to accumulate high stress with low strain rate. The vast strain energy accumulated In the long-term deformation within the Songpan-Garze block should be the dynamic source of the Wenchuan great earthquake.

The 3D P-wave velocity structure of the crust and upper mantle within the depth range of 400 km was obtained by using teleseismic traveltimes data recorded by West Sichuan Seismic Array distributed in Longmenshan region and non-linear tomography inversion technique. For adapting to the complicated structure, the fast marching traveltime calculation method and Tarantola's inversion method was used. Our results show the tectonic differences of the crustal and upper-mantle structure among the blocks of Chuandian, Songpan-Garze and Sichuan basin. Our results show that: 1) the crustal structure of the study area correlates with the surface geological features. The Sichuan basin is imaged as a high-velocity feature, while the Songpan-Garze and Chuandian black as low-velocity feature. The lithosphere thickness of Sichuan basin has lateral variations from 250 km in south part to 100 km in north part. There exist upwelling features under Songpan-Garze block. 2) Sichuan basin vertically contacts With Chuandian block, but the thickness of Sichuan basin front in Longmenshan area decreases from east to west with the feature of Songpan-Garze block incursion into Sichuan basin at upper mantle. This feature shows the difference in dynamic mechanism between Sichuan basin with Chuandian block and Sichuan with Songpan-Garze block. 3) The Longmen Shan faults belt is divided into two parts at Yingxiu: the south part and north part. The great Wenchuan earthquake and aftershocks distribute in the north part of Longmen Shan faults. The eastward extrusion of Tibetan plateau and upper mantle upwelling caused the uplifting of Songpan-Garze block. Because Yingxiu is located in the south edge of north part of Longmenshan faults belt, it's possible to accumulate high stress. This should be the deep dynamic background of the Wenchuan earthquake. Based on our results, the velocity structure does not support the subduction of the Sichuan basin downward and channel flow.