基于接收函数的华南及邻区地壳结构研究

利用华南地块及邻区2007~2012年609个地震台站记录的约900个5.7级以上远震事件,获得各台站的接收函数,通过分析接收函数的形态变化了解各台站下方的地壳结构特征,然后再利用H-κ叠加搜索技术获得各台站下方的地壳厚度和波速比。结果显示,研究区的地壳结构表现为从沿海向内陆逐渐复杂的变化,地壳厚度也表现出由沿海向内陆、自南向北逐渐增厚的趋势;研究区内的广东、福建、浙江、上海、江西、广西、安徽南部、湖北中东部、湖南中东部和云南东南部地区主要表现为标准型接收函数,地壳相对稳定,地壳厚度一般在35 km以下;研究区内的湖北西部、湖南西部、贵州、云南东部及中北部地区主要表现为过渡型接收函数,对应地壳增厚变形的区域,该区地壳厚度从约35 km逐渐增厚到约45 km;研究区内的重庆、四川、陕西南部、甘肃南部和云南北部主要表现为复杂型接收函数,对应地壳剧烈增厚的区域,地壳厚度从45 km增厚到60~70 km。     

华南大陆东部赣闽地区地壳厚度与泊松比研究

通过收集江西省和福建省共58个固定台站记录到的2011-01～2012-12的远震数据,利用接收函数H-κ扫描叠加方法得到台站下方平均地壳厚度和波速比估计,并通过插值得到华南大陆东部赣闽地区整体的地壳厚度变化趋势以及泊松比分布情况。结果表明,研究区地壳厚度约为28～34 km,由内陆向沿海有起伏地逐渐减薄,赣南地区同福建沿海地区地壳厚度较薄,江西东部和福建西北部地壳较厚;泊松比约为0.21～0.28,由内陆向沿海逐渐增加,赣北地区泊松比值最低,低于0.23（波速比低于1.70）,沿海地区泊松比较高,可达0.28（波速比为1.83）。并探讨了造成地壳厚度和泊松比变化的构造因素。     

深地震测深揭示的济阳坳陷地壳结构特征

对穿过济阳坳陷的3条深地震测深剖面进行解释、对比分析显示,济阳坳陷地壳结构分为上、中、下3层,莫霍面深度在31 km左右,区域起伏变化不大,深浅部构造呈镜像对称关系。济阳坳陷内中地壳存在低速体发育,为其顶面滑脱层的发育以及滑脱构造的形成提供了必要条件,也导致上下地壳厚度的横向变化存在差异。惠民凹陷下方Pm震相之前出现P4震相表明,其莫霍面以壳幔过渡带形式存在;东营凹陷下方Pm震相尖锐,其莫霍面则表现为一级间断面性质,体现了不同凹陷深部壳幔作用的差异。结论表明,济阳坳陷地壳结构具有典型的华北地区地壳结构特征,上下地壳厚度横向变化差异与滑脱构造密切相关,而莫霍面性质差异与深部软流圈上涌以及下地壳小规模拆沉有关。     

滇西北三江并流地区地壳S波速度结构北大核心CSCD

对滇西北三江并流地区36个台站记录的远震波形数据进行处理,提取径向P波接收函数,基于中国地震科学实验场地区地壳剪切波速模型获取不同区域的初始模型,采用时间域线性反演方法和bootstrap重采样技术,反演各台站下方的S波速度结构。结果表明:1)研究区地壳S波速度结构整体以澜沧江断裂带和27.5°N为界,表现出明显的区域差异。在上地壳,S波速度在0~25 km深度范围内存在由地表向壳内延伸的低速层,但不同区域低速层厚度存在较大差异,27.5°N以北低速层较为发育,厚度在20~25 km之间;27.5°N以南,澜沧江断裂带东西两侧低速层厚度差异明显,断裂带以西在10~25 km之间,断裂带以东约4 km。2)在下地壳,S波速度在横向上以澜沧江断裂带和27.5°N为界,表现出NE与SW区域以相对低速为主,NW和SE区域以相对高速为主的分布特征;垂向上,怒江断裂带中南部和金沙江-红河断裂带北端附近局部区域25~45 km深度范围内存在低速体,与上地壳低速层相连。3)澜沧江断裂带为地壳厚度和S波速度变化的重要分界面,对滇西北三江并流地区的构造演化过程具有控制作用。     

浙江省深部地球物理研究新进展──屯溪—温州、诸暨—临海地学断面及区域重力研究成果

本文通过屯溪—温州、诸暨—临海两大剖面的重力、地磁、大地电磁的实测与研究。首次采用爆破地震、MT等当代物探新技术及综合物探等方法。横穿扬子、华南两微板块北东缘结合部，获取了地壳和上地慢结构的信息，指出浙江省域地壳呈5层结构，莫震面平均理深32km；发现了莫霍面附近的推覆析离构造。重新探讨了江山—绍兴等几条重要骨架断裂的位置与产状，确认了江山—绍兴、余姚—丽水断裂为超壳断裂。计算了剖面和浙东陆域区的火山岩厚度（一般在3km以内）；讨论了地壳深浅不同层次的主要推覆构造：在浙江区域地壳浅部存在江山—绍兴、江山廿八都—石浦、泰顺—黄岩3个推覆构造；证实浙江地壳深部构造总体框架为“两拗三隆”──浙北幔隆、萧山—常山鼻状幔隆、沿海幔隆、皖浙边界地幔坳陷及奉化—庆元幔坳陷等重要成果。为本区进一步开展地球科学研究，核电站等大型工程的选址，指导深部找矿提供了系统的综合物探资料，并对浙江一些基底构造进行延伸解释增强了结论的科学性。     

InSAR约束下2001年昆仑山MS 8.1地震震后粘弹性松弛效应

根据2001年昆仑山MS8.1地震震后2~6 a的InSAR形变场,采用震后粘弹性松弛模型进行模拟,使用半解析平面分层模型研究青藏高原昆仑山地震震区流变结构。Maxwell半空间粘弹性应力松弛模型模拟结果表明,最优的弹性上地壳厚度为15~20 km,莫霍面深度为70 km,该地区下地壳有效粘滞系数在（1~2.5）×1019 Pas之间,上地幔有效粘滞系数在（1~6.3）×1019 Pas之间。该结果与青藏高原玛尼震区的震后粘弹性松弛反演结果基本一致。     

辽宁及邻区S波速度结构反演

利用辽宁及邻区70台地震仪2012年噪声连续波形记录,基于背景噪声层析成像法获取研究区下方10~40 s的相速度结构。利用得到的基阶面波相速度频散曲线,通过马尔科夫链蒙特卡洛(MCMC)法反演研究区下方10~40 km深度处的三维S波速度结构。结果表明,研究区浅层及中上地壳的S波速度分布与地形地貌有较好的对应关系,高低速过渡带更易形成孕震区。中下地壳至上地幔顶部的S波速度结构更多受控于莫霍面的起伏状态及深大断裂。海城至大连最后延伸至辽东湾的区域下方30~40 km深度范围内一直存在一个“弧形”的低速异常体,推测该区域存在热物质上涌现象。纵剖面C-C′的辽阳至伊通段下方15 km处存在椭圆形低速体。     

利用HVSR法探测渭河盆地浅部构造

利用渭河盆地眉县至扶风段地震测线的连续地震背景噪声数据,基于噪声水平和垂直向谱比（HVSR）法,得到各台站HVSR曲线;再通过频率与深度的转换关系,获得测线下方近地表第四系沉积层结构埋深。结果显示,盆地第四系沉积层厚度呈U型分布,由盆地两侧向中间腹部逐渐变厚,两侧厚度为100~400 m,中部厚度为400~600 m;沉积层深度剖面在距测线起点25 km和33 km处明显表现出沉积界面间断跳跃特征,该变化与岐山-马召断裂和扶风-乾县断裂在空间位置上有较好的一致性。     

北部湾大陆边缘地壳结构特征

文章利用天然地震的PS转换波研究了北部湾陆缘地区的地壳结构特征.PS转换波测量表明:本区地壳内部存在4个明显的转换界面:PSC、PSG、PSM、PSM1,分别代表上地壳、中地壳底界以及Moho面(下地壳底界)和上地幔顶部的第一转换面.计算结果表明,本区上地壳厚约12 km,中地壳厚约9 km,下地壳厚约11 km,Moho面深约32 km.地壳厚度(或Moho面深度)由海向陆变厚(或变深),由内陆的灵山到海陆交界处的北海、合浦,Moho面深度(或地壳厚度)由34 km变为30 km左右.PS转换波测深结果还表明,本区内NE向钦防-灵山断裂、合浦-博白断裂以及NW向小董-合浦断裂向深部延至中地壳,属壳断裂性质.北部湾陆缘地壳性质上仍为陆壳,由陆向洋明显减薄,北部湾盆地发育于这一减薄陆壳的前缘,是由地壳进一步伸展减薄所形成的.     

北天山地区近期重力场及地壳密度变化特征研究

利用2014~2019年北天山地区流动重力资料,采用绝对重力控制进行经典平差计算,获取该地区重力场时空演化特征图像,并结合重力段差可视化方法,得到该地区重点构造部位物质迁移规律。采用紧凑反演方法进行北天山中段不同深度地壳密度模拟计算,结果表明,北天山中段地壳物质密度变化最佳深度为30~40 km,是地壳密度变化的正值区域,基本位于北天山北坡和准噶尔盆地南缘,表明该地区物质不断汇聚,或者表明地壳呈现下沉的趋势;而在北天山山体附近,物质密度变化为负值,表明山体物质处于亏损态势,或者山体受到构造应力的作用,使地壳处于不断隆升过程中。     

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张渤地震构造带中西段及邻区深部构造探测

利用穿过张渤地震构造带中西段及邻区的多条地震测深资料．详细研究了张渤地震构造带中西段及邻区的地壳深部速度结构与构造。结果表明,该区地壳深部速度结构与构造在纵向和横向上具有明显的不均一性。在三河-平谷8级震区、延庆-怀来盆地及张家口附近地区莫霍面埋深分别为35、39和42km,其地壳厚度由东至西逐渐增加。该区基底断裂发育。在其深部,根据地震波动力学及运动学特征和二维速度结构中的地震界面与速度等值线起伏变化推测,在大兴、延庆、涿鹿等地均存在深部断裂带,在深部断裂带一侧或两侧的上地壳存在6．0km／s左右的低速层（体）。     

Thermo-Rheological Structure and Passive Continental Margin Rifting in the Qiongdongnan Basin,South China Sea,China

To investigate the thermo-rheological structure and passive continental margin rifting in the Qiongdongnan Basin(QDNB),thermo-rheological models of two profiles across the western and eastern QDNB are presented.The continental shelf of western QDNB,having the lowest crustal extension factor,is recognized as the initial non-uniform extension crust model.This regime is referred to as the jelly sandwich-1(JS-1)regime,having a lower crustal ductile layer.The oceanward part of the western QDNB changes from the relatively strong JS-1 to the weak crème br?lée-1(CB-1)regime with a significantly thinned lower crust.However,the crustal extension in the eastern QDNB is significantly higher than that in the western QDNB,with conjugate faults extending deep into the lower crust.The central depression zone of the eastern QDNB is defined as the much stronger JS-2 regime,having a brittle deformation across the entire crust and upper mantle and characteristics of a cold and rigid oceanic crust.Unlike the widespread lower crustal high-velocity layers(HVLs)in the northern margin of the South China Sea,the HVLs are confined to the lower crustal base of the central depression zone of the QDNB.The HVLs of QDNB are the results of non-uniform extension with mantle underplating during the lower crustal-necking stage,which is facilitated by the lower crustal ductile layer and derived by mantle lat-eral flowing.The gigantic mantle low-velocity zone related to the Red River Fault should be a necessary factor for the east-west differential margin rifting process of QDNB,which may drive the lateral flowing in the mantle.     

江汉盆地东北缘现今地壳构造应力场及其发震构造

基于湖北省区域测震台网数字波形数据,利用震源机制解获取江汉盆地东北缘现今地壳构造应力场。结果表明,研究区内地壳受力源影响发生自NWW向SEE方向位移,使得皂市断裂和长江埠断裂在4~6 km深度范围内发生以走滑为主、兼少量逆冲的剪切破坏,震群活动与古近纪以来的断层活动有关。     

Crustal structure revealed by a deep seismic sounding profile of Baijing-Gaoming-Jinwan in the Pearl River Delta

The Pearl River Estuary area, located in the middle part of the southern China coastal seismic belt, has long been considered a potential source of strong earthquakes above magnitude 7.0. To scientifically assess the potential strong earthquake risk in this area, a three-dimensional artificial seismic sounding experiment, consisting of a receiving array and seabed seismograph, was performed to reveal the deep crustal structure in this region. We used artificial ship-borne air-gun excitation shots as sources, and fixed and mobile stations as receivers to record seismic data from May to August 2015. This paper presents results along a line from the western side of the Pearl River Estuary to the western side of the Baijing-Gaoming-Jinwan profile. A two-dimensional velocity structure was constructed using seismic travel-time tomography. The inversion results show that the Moho depth is 27 km in the coastal area and 30 km in the northwest of the Pearl River Estuary area, indicating that the crust thins from land to sea. Two structural discontinuities and multiple low-velocity anomalies appear in the crustal section. Inside both discontinuity zones, a low-velocity layer, with a minimum velocity of 6.05 km s~(-1), exists at a depth of about 15 km, and another, with a minimum velocity of 6.37 km s~(-1), exists at a depth of about 21.5 km between the middle and lower crust. These low velocities suggest that the discontinuities may consist of partly molten material. Earthquakes with magnitudes higher than 5.0 occurred in the low-velocity layer along the profile. The deep Kaiping-Enping fault, rooted in the crust, may be one of the most important channels for deep material upwelling and is related to tectonic movement since the Cretaceous in the Pearl River Delta tectonic rift basin.     

VARIATIONS IN CRUSTAL THICKNESS OF THE KANE TRANSFORM IN THE NORTH ATLANTIC OCEAN

A new approach was taken to investigate the crustal stucture of the Kane transform and its aseismic extension, using high quality bathymetry and gravity data. The gravity signatures associated with variations in crustal thickness of the transform were isolated from the observed free-air anomaly,was continued downward to the mean depth of the crust/mantle interface and converted on to the relief onthat surface. The crustal thickness of the transform was then calculated by subtracting seawater depth from the depth of the gravity-inferred crust/mantle interface. 3-D gravity investigation results indicate that the Kane transform and adjacent areas are associated with a crust thinner than normal oceanic crust. The transform trough is largely underlain by a crust less than 4.5kin thick and in the nodal basins the crust may be as thin as 3 kin. The crust beneath the fracture zone valley is 4 - 5.5 km thick. The rift valleys on the spreading segments are also characterized by thin crust (4 - 5 km thick). Thin oceanic crust extends to 20-30 km from the transform axis,except for some localized places such as the inside comerhighs adjoining the ridge-transform intersections. These gravity-inferred results match fairly well with limited published seismic results. Thinning of the crust is mainly attributable to a thin layer 3, which in turn may be explained by the combined effects of reduced magma supply at the ends of the spreading segments and tectonic activities in the region.     

济阳坳陷上地壳速度结构与地热相关性研究

济阳坳陷及周边地区位于华北板块东部,是板内伸展沉积构造。目前研究区水热型地热资源开发利用程度较高,但上地壳热源传导机制研究较少,济阳坳陷及周边地区的高分辨率三维地壳速度结构有助于探讨该区热源富集规律。利用双差层析成像方法,获得了研究区三维地壳的速度结构,通过与地温场特征比对分析,认为上地壳速度结构与深部热源传导规律密切相关。根据反演结果,发现聊考-齐广断裂西北0～5km深度存在大规模低速层,这与区域厚度较大的沉积地层有关;聊城东部、埕宁隆起等区域表现为明显的高速异常,隆起区地温增温率明显高于凹陷区,这与储层下部地层导热能力有关;东营地区10km以下速度普遍较高,下地壳热流值贡献稳定;燕山晚期以来鲁中南部隆起对研究区地壳的拖拽拉伸是济阳坳陷内地热田最直接的构造影响因素,形成的多组地堑构造是水热型沉积盆地地热田边界的重要控制因素。