An explosive seismic sounding profile across the transition zone between west Kunlun Mts. and Tarim Basin

The explosive seismic sounding profile across the transition zone from the west Kunlun Mts. to the Tarim Basin revealed the complex deep structure formed by continent-continent collision on the northern margin of the Tibetan Plateau. The profile shows that the attitude of the Moho is in agreement with that of the crystalline basement in the Tarim Basin and the whole crust dips as a thick slate southwards with an angle from 5° to 7°. Meanwhile, the Moho depth increases from 40 km to 57 km within a distance of 150 km in the southern Tarim region, depicting the subduction of the crust of this region towards the west Kunlun Mts. The crust of the northern slope of the west Kunlun Mts. shows an evident compressed and shortened feature, that is, the basement is uplifted, the interface dips northwards and the Moho rises abruptly to become flat, so that the lower crust is as thick as 20 km.     

FAULT GEOMETRY DEFINED BY MULTIPLE REMOTE SENSING IMAGES INTERPRETATION AND FIELD VERIFICATION: A CASE STUDY FROM SOUTHERN GUANGGAISHAN- DIESHAN FAULT,WESTERN QINLING

The NE margin of Tibetan plateau outspreads northeastward in late Cenozoic. The west Qinling locates at intervening zone among Tibetan plateau, Sichuan Basin and Ordos block, and is bounded by East Kunlun Fault in the southwest, the north margin of West Qinling Fault in the northeast, and the Longmen Shan Fault in the southeast. The west Qinling has been experiencing intense tectonic deformation since late Cenozoic, accompanying by uplift of mountains, downward incision of rivers, frequent moderate-strong earthquakes, vertical and horizontal motion of secondary faults, and so on. A series of "V-shape" faults are developed in the transfer zone between East Kunlun Fault and north margin of West Qinling Fault. The NWW-NW striking faults include Tazang Fault, Bailongjiang Fault, Guanggai Shan-Die Shan Fault, and Lintan-Dangchang Fault; EW-NEE-NE striking faults include Ha'nan-Qingshanwan-Daoqizi Fault, Wudu-Kangxian Fault, Liangdang-Jiangluo Fault, and Lixian-Luojiapu Fault. Among them, the Southern Guanggai Shan-Die Shan Fault (SGDF)is one of the principle branch which accommodates strain partitioning between the East Kunlun Fault and the north margin of west Qinling Fault. Although some works have been done and published, the geometry of SGDF is still obscure due to forest cover, bad traffic, natural and manmade reworks. In this paper, we collected remote sensing images with various resolutions, categories, imaging time. The selected images include composite map of Landsat image (resolution is 28.5m among 1984-1997, and 14.5m among 1999-2003), Landsat-8 OLI image (15/30m), Gaofen-1 (2m/8m), Pleiades (0.5m/2m), DEM (~25m)and Google Earth image (submeter resolution). After that, we reinforced tectonic information of those images by Envi5.2 software, then we interpreted SGDF from those images. As indoor interpretation fulfilled, we testified indoor interpretation results through geomorphological and geological investigation. Finally, we got fault distribution of SGDF. Conclusions are as follows:First, remote sensing image selection and management is crucial to indoor interpretation, and image resolution is the only factor we commonly consider before, however, things have changed in places where there is complex weather and dense vegetation. Image categories, imaging time and bands selected for compositing in pretreatment and etc. should all be taken into consideration for better interpretation. Second, SGDF distributes from Lazikou town in the west, extending through Pingding town, Zhou County, Huama town, then terminating at Majie town of Wudu district in the east, the striking direction is mainly NWW, and it could be roughly divided into 3 segments:Lazikou-Heiyusi segment, Pingding-Huama segment, and Huama-Majie segment, with their length amounting to 47km, 32.5km, 47km, respectively. The arrangement pattern between Lazikou-Heiyusi segment and Pingding-Huama segment is right-stepping, and the arrangement pattern is left-stepping bending between Pingding-Huama segment and Huama-Majie segment. Third, SGDF controlled magnificent macro-topography, such as fault cliff, fault facet, which often constitute the boundary of intermontane basins or erosional surfaces to west of Minjiang River. Micro-geomorphic expressions were severely eroded and less preserved, including fault scarps, fault troughs, sinistral offset gullies and geomorphic surfaces. Finally, SGDF mainly expresses left-lateral dominated motion, only some short branch faults with diverting striking direction exhibit vertical dominated motion. The left-lateral dominated component with little vertical motion of SGDF is consistent with regional NWW-striking faults as Tazang Fault, Bailongjiang Fault and Lintan-Dangchang Fault, also in coincidence with regional boundary faults such as east Kunlun Fault and north margin of west Qinling Fault, illustrating regional deformation field is successive in west Qinling, and NWW striking faults show good inheritance and transitivity on differential slip rate between east Kunlun Fault and west Qinling Fault. The geometry of SGDF makes quantitative studies possible, and also provides scientific basis for keeping construction away from fault traces.     

西昆仑造山带下岩石圈地幔速度结构

在已完成的新疆地学断面研究计划实施中曾在西昆仑山前布置了14个宽频带地震台站.利用记录到的远震P波初至和层析成像方法，研究了西昆仑造山带下的岩石圈地幔结构特征.在已有地震学证据基础上，层析成像结果显示，西昆仑造山带下的高速岩石圈地幔可能是印度岩石圈地幔的俯冲前缘.沿东经80°深度剖面图像显示，在西昆仑造山带下的150～300km处，高速异常的岩石圈地幔前锋与低速异常的塔里木块体岩石圈地幔发生了面对面碰撞.     

THE TECTONIC ACTIVITY CHARACTERISTICS OF AWANCANG FAULT IN THE LATE QUATERNARY,THE SUB-STRAND OF THE EASTERN KUNLUN FAULT

It is well known that the slip rate of Kunlun Fault descends at the east segment, but little known about the Awancang Fault and its role in strain partitioning with Kunlun Fault. Whether the sub-strand(Awancang Fault) can rupture simultaneously with Kunlun Fault remains unknown. Based on field investigations, aerial-photo morphological analysis, topographic surveys and ¹⁴C dating of alluvial surfaces, we used displaced terrace risers to estimate geological slip rates along the Awancang Fault, which lies on the western margin of the Ruoergai Basin and the eastern edge of the Tibetan plateau, the results indicate that the slip rate is 3mm/a in the middle Holocene, similar to the reduced value of the Kunlun Fault. The fault consists of two segments with strike N50° W, located at distance about 16km, and converged to single stand to the SE direction. Our results demonstrate that the Awancang fault zone is predominantly left-lateral with a small amount of northeast-verging thrust component. The slip rates decrease sharply about 4mm/a from west to east between the intersection zone of the Awancang Fault and Kunlun Fault. Together with our previous trenching results on the Kunlun Fault, the comparison with slip rates at the Kunlun fault zone suggests that the Awancang fault zone has an important role in strain partitioning for east extension of Kunlun Fault in eastern Tibet. At the same time, the 15km long surface rupture zone of the southeast segment was found at the Awancang Fault. By dating the latest faulted geomorphologic surface, the last event may be since the 1766±54 Cal a BP. Through analysis of the trench, there are four paleoearthquake events identified recurring in situ on the Awancang Fault and the latest event is since (850±30)a BP. The slip rate of the Awancang Fault is almost equivalent to the descending value of the eastern part of the east Kunlun Fault, which can well explain the slip rate decreasing of the eastern part of the east Kunlun Fault(the Maqin-Maqu segment)and the characteristics of the structure dynamics of the eastern edge of the Tibet Plateau. The falling slip rate gradient of the eastern Kunlun Fault corresponds to the geometric characteristic. It is the Awancang Fault, the strand of the East Kunlun Fault that accommodates the strain distribution of the eastward extension of the east Kunlun Fault. This study is helpful to seismic hazard assessment and understanding the deformation mechanism in eastern Tibet.     

ELECTRICAL STRUCTURE OF THE 2017 MS7.0 JIUZHAIGOU EARTHQUAKE REGION AND THE EASTERN TERMINUS OF THE EAST KUNLUN FAULT

The East Kunlun Fault is a giant fault in northern Tibetan, extending eastward and a boundary between the Songpan-Ganzi block and the West Qinling orogenic zone. The East Kunlun Fault branches out into a horsetail structure which is formed by several branch faults. The 2017 Jiuzhaigou M_S7.0 earthquake occurred in the horsetail structure of the East Kunlun Fault and caused huge casualties. As one of several major faults that regulate the expansion of the Tibetan plateau, the complexity of the deep extension geometry of the East Kunlun Fault has also attracted a large number of geophysical exploration studies in this area, but only a few are across the Jiuzhaigou earthquake region. Changes in pressure or slip caused by the fluid can cause changes in fault activity. The presence of fluid can cause the conductivity of the rock mass inside the fault zone to increase significantly. MT method is the most sensitive geophysical method to reflect the conductivity of the rock mass. Thus MT is often used to study the segmented structure of active fault zones. In recent years MT exploration has been carried out in several earthquake regions and the results suggest that the location of main shock and aftershocks are controlled by the resistivity structure. In order to study the deep extension characteristics of the East Kunlun Fault and the distribution of the medium properties within the fault zone, we carried out a MT exploration study across the Tazang section of the East Kunlun Fault in 2016. The profile in this study crosses the Jiuzhaigou earthquake region. Other two MT profiles that cross the Maqu section of East Kunlun Fault performed by previous researches are also collected. Phase tensor decomposition is used in this paper to analyze the dimensionality and the change in resistivity with depth. The structure of Songpan-Ganzi block is simple from deep to shallow. The structure of West Qinlin orogenic zone is complex in the east and simple in the west. The structure near the East Kunlun Fault is complex. We use 3D inversion to image the three MT profiles and obtained 3D electrical structure along three profiles. The root-mean-square misfit of inversions is 2.60 and 2.70. Our results reveal that in the tightened northwest part of the horsetail structure, the East Kunlun Fault, the Bailongjiang Fault, and the Guanggaishan-Dieshan Fault are electrical boundaries that dip to the southwest. The three faults combine in the mid-lower crust to form a "flower structure" that expands from south to north. In the southeastward spreading part of the horsetail structure, the north section of the Huya Fault is an electrical boundary that extends deep. The Tazang Fault has obvious smaller scale than the Huya Fault. The Minjiang Fault is an electrical boundary in the upper crust. The Huya Fault and the Tazang Fault form a one-side flower structure. The Bailongjiang and the Guanggaishan-Dieshan Fault form a "flower structure" that expands from south to north too. The two "flower structures" combine in the high conductivity layer of mid-lower crust. In Songpan-Ganzi block, there is a three-layer structure where the second layer is a high conductivity layer. In the West Qinling orogenic zone, there is a similar structure with the Songpan-Ganzi block, but the high conductivity layer in the West Qinling orogenic zone is shallower than the high conductivity layer in the Songpan-Ganzi block. The hypocenter of 2017 M_S7.0 Jiuzhaigou earthquake is between the high and low resistivity bodies at the shallow northeastern boundary of the high conductivity layer. The low resistivity body is prone to move and deform. The high resistivity body blocked the movement of low resistivity body. Such a structure and the movement mode cause the uplift near the East Kunlun Fault. The electrical structure and rheological structure of Jiuzhaigou earthquake region suggest that the focal depth of the earthquake is less than 11km. The Huya Fault extends deeper than the Tazang Fault. The seismogenic fault of the 2017 Jiuzhaigou earthquake is the Huya Fault. The high conductivity layer is deep in the southwest and shallow in the northeast, which indicates that the northeast movement of Tibetan plateau is the cause of the 2017 Jiuzhaigou earthquake.     

青藏高原东北缘—鄂尔多斯地块地壳上地幔S波速度结构

1999～2000年从青海玛沁到陕西榆林，横跨青藏高原东北缘和鄂尔多斯布设了一条由47台宽频带数字地震仪组成的长约1000km的流动地震台阵观测剖面.利用记录到的远震体波波形资料和接收函数方法获得了剖面下0～100km深度的地壳和上地幔S波速度结构.结果表明，沿观测剖面地壳结构显示了明显的分块特征; 地壳厚度自东向西由40km增加到64km左右；在海原地震带下方和西秦岭断裂以西到日月山断裂之间的区域Moho间断面结构复杂；在1920年海原震区及其西侧，上地壳存在明显的低速层，在该地区的绝大部分地震分布在该低速层东边界偏向高速区一侧；祁连山东缘Moho面有约4km的深度间断，壳内向西逐渐减薄的低速层内有大量微震发生，沿祁连山的逆冲加走滑的构造运动在深度上已经穿透了Moho面；在玛沁断裂和日月山断裂之间，上地壳存在厚度很大的低速层，同时该区域下地壳也明显加厚.研究结果表明，青藏高原东北缘与鄂尔多斯地块之间的过渡带地壳变形强烈，地壳结构较为破碎，这与该地区地震频发相一致.     

青藏高原东北缘岩石圈厚度与上地幔各向异性

利用青海地震台网和甘肃地震台网2007-2009年记录的远震波形资料,提取S波接收函数和SKS分裂参数,得到了青藏高原东北缘的三维岩石圈厚度分布和上地幔各向异性特征.S波接收函数结果表明:昆仑-阿尼玛卿缝合带以南的松潘-甘孜地块东北缘和西秦岭造山带下方岩石圈较薄,厚度为125~135 km;昆仑-阿尼玛卿缝合带以北具有较厚的岩石圈,在昆仑和祁连地块下方岩石圈厚达145~175 km,并向柴达木盆地(175~190 km)和克拉通(鄂尔多斯南部约为170 km、阿拉善南缘约为200 km)下方增厚.上地幔各向异性结果显示:东北缘地区的SKS快波偏振方向为NW-SE向,与前人得到的昆仑断裂带南侧的快波方向存在较大差异,南侧自高原内部呈顺时针旋转,表明昆仑断裂带可能为上地幔变形的转换带.SKS快、慢波延迟时间为0.8~1.9 s,且在昆仑-阿尼玛卿缝合带以北,延迟时间与岩石圈厚度呈正相关关系,推断该区各向异性主要来源于地幔盖层的初期伸展变形.     

台湾-阿尔泰地学断面阿尔金-龙门山剖面的地壳纵波速度结构

通过分析阿尔金—龙门山地学断面的地震资料,建立了该剖面的地壳纵波速度结构。研究结果表明,阿尔金北侧的塔里木盆地地区莫霍面为50km,而在其南侧的祁连地块莫霍面突然加深至73km,在柴达木盆地莫霍面又抬升至58km左右,然后,在松潘甘孜地块莫霍面降至70km,并呈现为台阶状向龙门山方向抬升到60km左右,最低速层,而在其南部地区则没有低速层出现,推测低速层为地壳中部的局部熔融物质,阿尔金—龙门山剖面上的两个莫霍面坳陷区分别与祁连地块和松潘—甘孜地块上的两个莫霍面坳陷区相对应,指示出这个两个地块具有较深的山根,青藏高原北部的巨厚地壳很可能是由于中生代以来发生的印度板块与亚洲板块碰撞时受到来自东西及南北方向的挤压,使地壳缩短所致。     

东昆仑活动断裂带东段全新世滑动速率研究

文中通过对东昆仑活动断裂带托索湖至玛曲段的实际野外测量,获得了该段上的1组断裂位错实测数据和14C及TL测年样品。通过室内分析研究,发现大体以阿尼玛卿山玛积主峰为界,东昆仑活动断裂带托索湖至玛曲段可再分为花石峡段和玛沁段2个在几何上不连续的段落,花石峡段的全新世水平滑动速率(115±11)mm/a明显高于玛沁段(70±06)mm/a。此外,由于断裂而引起的断裂两侧的差异垂直隆升速率,花石峡段自4kaBP以来约为(21±03)mm/a,玛沁段自10kaBP以来约为055mm/a。这种差异垂直隆升速率的明显变化,一方面反映了东昆仑活动断裂带不同段落上活动的差异,另一方面也可能反映了研究区内全新世以来的快速隆升     

The Zoige fifteenth-century 7.2 earthquake ruptures on the Eastern Kunlun Fault,China

Journal of Seismology - The Kunlun Fault System (KFS), situated on the northern border of the Bayan Har block, central-eastern Tibetan Plateau, is among the most important active regional transform...     

Analysis of the lithospheric magnetic anomalies and tectonics in continental China and the adjacent regions using CHAMP satellite data

In this paper, the CHAMP satellite data from the last decade are used to map the lithospheric magnetic field in continental China at altitudes of 300 and 400 km using the spline function model technique. The results show that our model has higher amplitude than the spherical harmonic magnetic field model MF7. The resulting lithospheric anomaly distribution of continental China agrees with the geotectonic structure and crustal thermal structure. The magnetic anomaly distribution clearly indicates extrusion of the Tibetan Plateau towards the northeast and northwest directions. Northward movement is impeded by the relative rigid Tarim Basin featured with positive magnetic anomalies. The positive magnetic anomalies in Tarim basin extend to the northern Tibetan Plateau, suggesting that the southern part of Tarim Basin underthrusted the northern Tibetan Plateau.     

利用远震P波层析成像研究巴颜喀拉地块东缘及邻区的深部结构

为了揭示巴颜喀拉地块东缘及邻区的壳幔速度结构差异,获取2017年九寨沟M_S7.0地震的深部构造背景,本文收集了2009年5月至2016年8月期间四川及邻区数字测震台网的203个地震台站所记录到的远震P波走时数据,应用有限频体波走时层析成像方法,反演得到了巴颜喀拉地块东缘及邻区50—600 km深度范围内的三维壳幔P波速度结构。反演结果表明:巴颜喀拉地块东缘及邻区的壳幔速度结构具有明显的横向不均匀性和分区特征,松潘—甘孜地槽褶皱系、西秦岭和祁连山褶皱系的整体速度异常较低,研究区东部具有克拉通性质的四川盆地西北缘和鄂尔多斯地块南缘则呈明显的高速异常。上地幔P波速度结构特征差异表明松潘—甘孜地块的抬升可能与地幔上涌有关,巴颜喀拉地块东缘九寨沟震区及周边50—250 km深度范围内的上地幔存在低速异常,在400—600 km地幔过渡带深度范围内表现为明显的高速异常特征。巴颜喀拉地块向东南方向运移受到东部高速、高强度的扬子克拉通地块对青藏高原物质东向挤出的强烈阻挡,而九寨沟震区处于松潘—甘孜地块重要的北东边界断裂交会处附近,应力容易在此集中,这些因素均可能是东昆仑断裂塔藏段与岷江断裂北段交会处附近发生九寨沟M_S7.0地震的深部动力学背景。      

2014年2月12日新疆于田Ms7．3地震发震构造初步研究

2014年2月12日新疆和田地区于田县Ms7．3地震发生在塔里木盆地的南边,昆仑山区海拔4500m左右地带,青藏高原边界的阿尔金断裂带。阿尔金断裂带属于大陆内巨型断裂带,绵延1600km,此次地震位于阿尔金断裂带的西南段,震区内断裂带呈放射状,由多条断裂构成,规模较大,根据震源机制解得到本次地震为左旋走滑破裂形式。结合GF-1高分辨卫星数据,对比震前、后影像,在硝尔库勒盆地南缘断裂带发现一系列新的地表破裂带。     

2001年11月14日新疆青海交界东昆仑山8.1级地震构造背景初探

2 0 0 1年 11月 14日中国新疆青海交界昆仑山中的 8.1级地震发生在东昆仑断裂的西段。这是一条大型活动块体边界断裂。青藏高原东北部向东逃逸而产生左旋剪切运动使该断裂成为一条青藏高原北部强震密集带。这次地震震中在北西西向东昆仑断裂与北东东向次级断裂的交汇部位 ,破裂表现为自西向东单向扩展的特点     

青藏高原及邻近区域的S波三维速度结构

本文收集了WWSSN台网和我国台网中13个地震台站的长周期地震记录,用140条10-90s瑞利波频散曲线和作者提出的Tarantola-Backus面波频散层析成象方法,作了青藏高原及邻区的速度反演,得出该地区岩石层速度结构的三维图象.结果表明,1.在10-110km深度范围内,速度结构出现与大地构造特征相关的分区性,显示出四个构造单元:青藏块体、柴达木-巴颜喀拉-三江块体、塔里木块体和印度块体.2.高原内部,深度为10-70km内速度较低,莫霍界面呈不对称盆形分布,藏北那曲附近地壳厚度超过70km,高原边缘壳厚为45-50km,90-110km为高速异常,表明高原内部存在上地幔盖层.3.高原北部的班公湖断裂和东部的三江断裂系是该区重要的分界线,是岩石层结构存在明显差异的重要接触部位,可能是冈瓦纳古陆与欧亚古陆的缝合带.4.柴达木-巴颜喀拉-三江块体内部速度分布不均匀,地壳厚度由北向南从45km加深到60km;在深度90-110km存在一低速层.5.塔里木地块内速度随深度均匀增加,从地壳到上地幔110km内没有发现低速层.地壳厚度约50km.     

青藏高原S波和泊松比的层析成像

本研究使用中国数字地震台网（CDSN）（2009—2016）走时数据开展青藏高原地壳地震波速度三维层析成像研究,获得分辨率达到1°×1°×20 km的青藏高原地壳S波三维速度结构和泊松比分布.结果表明,分布在可可西里和羌塘北部的高钾质和钾质火山岩带,其上地壳到下地壳都存在S波波速扰动负异常和高泊松比.说明第三纪青藏高原隆升过程中,由于大陆碰撞使三叠纪的东昆仑缝合带重新破裂,造成大量壳幔混合熔融物质上涌和火山喷发,进而揭示了青藏高原北部新生代火山岩的存在与青藏高原的形成和隆升密切相关;青藏高原新生代裂谷位于中下地壳S波速度扰动负异常带的两侧,裂谷带之下的中下地壳泊松比减小到0.22以下.裂谷带之下中下地壳的S波速异常分布和泊松比值可以推断青藏高原新生代裂谷深达中地壳底部,这个推论与密度扰动三维成像的相关结论一致.青藏高原S波速度和泊松比在下地壳至壳幔边界随深度产生急剧变化,说明地壳内部发生了大规模的层间拆离和水平剪切;青藏高原东构造结之下泊松比高达0.29~0.33,S波速度扰动为负异常,推断东构造结下方地壳主要由坚硬的蛇纹石化橄榄岩组成;青藏高原中下地壳S波速负异常区范围大面积扩大,地壳底部几乎被S波速低值区全部覆盖.下地壳S波异常分布特点可能反映下地壳管道流的影响.     

阿尔金断裂带西段车尔臣河以西晚第四纪以来的滑动速率研究

通过分析阿尔金断裂带西段车尔臣河出山口以西 85°～ 86°E的高精度SPOT卫星影像 ,结合野外考察和年代学研究 ,对阿尔金断裂带西段 3个典型走滑断层的断错地貌进行了研究。在库拉木拉克 ,阿尔金断裂带西段自 (6 0 2± 0 4 7)kaBP以来的左旋滑动速率为 (11 6± 2 6 )mm/a ,自 (15 6 7± 1 19)kaBP以来的左旋滑动速率为 (9 6± 2 6 )mm/a ;阿羌牧场附近 ,自 (2 0 6± 0 16 )kaBP以来的左旋滑动速率为 (12 1± 1 9)mm/a ;达拉库岸萨依附近 ,自 (4 91± 0 39)kaBP以来的左旋滑动速率为(12 2± 3 0 )mm/a。由此得到阿尔金断裂带全新世以来的平均滑动速率约为 (11 4± 2 5 )mm/a。以阿尔金断裂带走向N75°E计算 ,阿尔金断裂带西段左旋走滑所吸收的青藏高原SN向缩短速率为 (3 0±0 6 )mm/a     

应用非连续性模型模拟断层活动对青藏高原应力应变场的影响

在青藏高原的运动变形过程中，断层活动起着至关重要的作用.本文利用有限元数值模拟的方法，分别计算了在GPS做边界约束下青藏高原及周边区域的连续体模型和含断层的不连续体模型的运动状态和应力场分布.从连续性模型和非连续体模型的差异发现，断层存在与否很大程度上影响了青藏高原现代运动场的分布.主要体现在，断层的滑移运动（1）增加了青藏高原东西两侧的拉张趋势；（2）加大了青藏高原物质东移的速度；（3）改变了塔里木和柴达木盆地的运动状态.模拟结果显示，非连续模型的运动场分布与GPS观测结果吻合程度大大高于连续体模型结果，表明断层活动在青藏高原的运动学和动力学过程中起着重要的作用，在研究青藏高原的动力学机制中，必须考虑断层作用的影响.     

对1937年托索湖7.5级地震若干问题的探讨

1937年托索湖7.5级地震发生在东昆仑活动断裂带的东段,前人曾对该地震组织过4次不同程度的考察,并得出了4种不同的结果。带着上述问题对该地震地表破裂带重新进行了实地考察、测量和综合研究,然后对该地震地表破裂带的西端点、最大左旋水平位移量、最大垂直位移量、宏观震中等问题进行了重新厘定,认为1937年托索湖7.5级地震地表破裂带西端点在阿拉克湖以西,长度至少为240km,最大左旋水平位移量为8m,垂直位移量为3.5m,宏观震中在三岔口一带     

青藏高原及邻近地区地壳与上地幔剪切波三维速度结构

本文利用30个基准台所记录的238条长周期面波资料,经过适配滤波和分格频散反演,得到中国大陆及邻区147个分格10-105s的纯路径频散,进而反演出青藏高原及邻近地区深至170km的剪切波三维速度结构.研究表明,青藏高原中西部地区和东部地区的地壳平均厚度分别为70±7km和65±7km,地壳平均剪切波速度分别为3.55和3.62km/s,上地幔顶盖平均速度分别为4.63和4.61km/s; 岩石层厚度均为120±10km;东部地区下地壳内30-40km深度处普遍存在低速层;青藏高原及其东侧的上地幔低速层内有横贯东西且明显向上隆起的低速腔.滇西缅北地区的地壳厚45±5km,上地壳及下地壳内都有低速层;上地幔顶盖的速度为4.42km/s,比青藏高原本体及恒河平原都低.恒河平原地壳厚34±2km,速度平均为3.45km/s;上地幔顶盖厚86±10km,速度平均为4.63km/s,顶盖内55-83km深处有一个低速夹层.