深地震探测揭示的华南地区莫霍面深度

从20世纪70年代以来, 在华南地区进行了大量的深地震探测研究。本文通过对华南地区的深地震探测研究的总结和梳理, 探讨了华南大陆及其邻近海域的莫霍面变化情况, 结果表明: 华南大陆莫霍面形态变化较大, 总体变化趋势是由西部向东部呈逐渐抬升; 华南大陆最深的莫霍面出现在攀西地区北缘, 最浅的莫霍面出现在衢州盆地, 两者差35 km; 华南地区周缘断裂均存在莫霍面错断; 华南加里东造山带莫霍面深度浅于台湾造山带; 东海边缘海与南海北缘地壳厚度明显不同。这些特征可能指示了不同区域所经历的岩石圈及地壳演化过程不同, 其中攀西地区的莫霍面较厚可能同青藏高原物质东流有关, 华南造山带的地壳减薄缘于后期遭受的伸展作用, 东海及南海的莫霍面深度反映了两者处于不同的陆缘位置, 前者为活动大陆边缘, 后者为被动大陆边缘。     

中国满洲里-绥芬河地学断面地震学研究

满洲里－绥芬河地学断面域地震学研究表明：沿断面可划分额尔古纳－大兴安岭、松辽盆地－张广才岭和佳木斯－兴凯三个波速块体;纵向上地壳分为三层,地壳厚度２９～３８ｋｍ;Ｐ波平均速度６．２５～６．４０ｋｍ／ｓ;松辽盆地沉积盖层较厚,基底面下方附近低角度断层发育;Ｍｏｈｏ面厚度１．５～５．０ｋｍ,内部结构复杂;上地幔低速层埋深差异较大,松嫩块体埋深最浅;深源地震频度高、强度大、震源深,浅源地震相对较少和较弱,震源多位于地壳中上部;地壳构造应力场主压应力优势方向为北东—南西。     

鹤岗矿区煤层气资源评估与开发前景预测

鹤岗矿区面积２５２ｋｍ＾２，有效井田面积为１００．２１ｋｍ＾２，含煤地层厚８００～１０００ｍ，共含煤４０层，含煤系数为４．３～９．３％，大于３．５ｍ的煤层占７５％，中厚煤层占１９．２％，其中可采煤层和局部可采煤层计３６层，总厚度为３８．６～８５．８ｍ，赋存深度均在１２００ｍ以内，煤炭资源量２５６５Ｍｔ，资源量密度为１０．１８Ｍｔ／ｋｍ＾２，煤层瓦斯含量为９．４～１５．５ｍ＾２／ｔ，平均为１３ｍ＾３     

长江三峡狮子口地区重力滑动构造研究

长江三峡工程坝址西南约１０ｋｍ的狮子口地区，发育一个长约８ｋｍ、宽约３ｋｍ的重力滑动构造系统。它由下伏系统、滑动系统和前缘推挤带构成，是一个典型的多层次滑褶型重力滑动构造。它形成时的温、压条件为１３０．５～１９３．７℃和１８０～２３０ＭＰａ；ｌ；形成深度约５～１０ｋｍ；总体岩层收缩量３２．２％；总滑移距离１０６０ｍ；活动时间上限１２７．６５士３８．２９万年。它是燕山运动期间南北向挤压体制下，在黄陵背斜东、西两侧应力屏蔽区内派生的近东西向拉伸构造应力场的产物。     

滇西无量山北缘弧形推覆构造

滇西无量山北缘弧形推覆构造是一个具有多重叠置结构的复杂推覆系统。原地系统为侏罗系和白垩系组成的北西西向弧形褶皱带。外来系统主要是上三叠统。总体上自南向北推覆，上盘向北北东方向推移距离１０ｋｍ。形成深度约５－１０ｋｍ，形成环境下超过绿片岩相。，大体生成于渐新世时期，约４０－２０Ｍａ之间。     

郯庐断裂带渤海段的深部构造特征──地壳厚度和居里面的研究结果

从居里等温面埋深和地壳厚度两方面论述郯庐断裂带渤海段的深部构造特征。根据航磁资料，运用三维磁性层反演方法，计算了研究海区居里面的深度；又根据布格重力异常资料，运用三维重力正、反演方法，计算了研究海区的地壳厚度。参考了地热和壳幔电性结构的有关数据，提出了对郯庐断裂渤海段深部构造特征的认识：①向东陡倾斜，这是居里面埋深和地壳厚度两个较为一致的结果；②分段性明显，显示了沿断裂带新生代以来地壳动力学特征是不同的。郯庐断裂在渤海可以分成三段，即渤海中段，居里面最浅（１３ｋｍ），地壳厚度最薄（２５ｋｍ），地壳运动以拉张为主；辽东湾段，居里面深度１６～１７ｋｍ，地壳厚度２８～３０ｋｍ；莱州湾段，居里面深度２０ｋｍ，地壳厚度３０～３２ｋｍ。     

东秦岭地区的地壳速度结构

对横穿秦岭东段的人工地震测深剖面进行二维射线追踪处理，得到了该剖面上的二维速度结构图。由此获知该地区的地壳呈多层结构。上层地壳的Ｐ波速度为４．０～５．５ｋｍ／ｓ；中层地壳中有低速层出现；下层地壳的速度变化不大，约为６．５～６．９ｋｍ／ｓ。在深部可能有三个错断莫霍面的断裂带。地壳中的速度出现分层的特点，可能是由大的推覆构造所致。     

岩石圈深部的水及其意义探讨

在对水的相图、典型地区的地温曲线、矿物的脱水行为及一些矿物和岩石的含水量等研究的基础上指出,以１５．５～２５．１ｋｍ深度为界,在该深度以上的岩石圈浅部水是液态,而在该深度以下的岩石圈深部水是气态,水以矿物的结构水形式被带入到１５．５～２５．１ｋｍ深度以下的岩石圈中,若矿物结构水完全脱出,在储冲带中水临界温度至矿物脱结构水的极限温度相对应的的区域内（如秦岭１５．５～６４．０ｋｍ）,平均含水量的０．５～１．０％,讨论了在岩石圈深部矿物脱水作用与局高压环境、高导低速带之间的成因联系。     

面波波形反演中的模拟退火法

采用求解非线性全局优化问题的模拟退火法作为反演手段,对面波波形进行反演,研究青藏高原地壳上地幔速度结构。通过青藏高原的面波波形振幔显示出在周期为２０ｓ和４０ｓ时存在两个极小值,这可能是由地壳中存在低速层引起的。而波波形反演得到的速度民证实了青藏高原在２０ｋｍ深度左右普遍存在低速层;喜马拉雅山造山带在６０ｋｍ深度附近了在一低速层,壳内低速层是青藏高原变形及隆升过程最重要的动力学边界条件之一。     

中国陆壳及其沉积层和上陆壳的化学元素丰度

中国陆壳的平均厚度为４７ｋｍ。其上地壳厚３１ｋｍ，沉积层厚５ｋｍ。质量分别为：中国陆壳１２．４３７×１０＾１＾７ｔ，上陆壳８．００５×１０＾１＾７ｔ，沉积层１．１４６×１０＾１＾７ｔ。上陆壳／下陆壳的质量比例为１．８：１。根据２２４６个岩石化学全分析资料和微量元素平均含量初充资料，求出了中国陆壳及其沉积和上陆壳的化学元素丰度。１３种常量元素的丰度总和，占中国陆壳质量的９９．６％，其余大量微量元素仅     

Lower-crust S-wave velocity beneath western Yunnan Province from waveform inversion of dense seismic observations

We use teleseismic body waveforms to explore S-wave layered velocity structures beneath 30 portable digital seismic stations deployed around western Yunnan Province. Results show that the Moho depth in this region is ∼40 km and decreases in general from north to south, consistent with previous geophysical studies. Associated with this lateral variation of the Moho depth, the lower crust above the Moho discontinuity has a 15–25 km thick zone with an S-wave velocity lower than that of the upper crust. This lower velocity zone might be interpreted as a lower crust weak channel, which may mechanically partially decouple the upper-crust deformation from the underlying mantle. Thus, the inverted S-wave velocity structure could provide new evidence for the lateral flow of lower crust in the build-up of the south-eastern Tibetan plateau.     

长江中下游成矿带及邻区地壳速度结构：来自利辛-宜兴宽角地震资料的约束

为了理解长江中下游地区在中生代成矿的深部动力学过程,Sinoprobe-03-02项目于2011年9月至10月,在跨宁芜矿集区和郯庐断裂带实施了从安徽利辛至江苏宜兴450km长的宽角反射/折射地震剖面。速度剖面结果显示,Moho面深度和地壳速度结构在郯庐断裂两侧东西方向存在明显的差异:(1)在东部扬子块体内部,地壳覆盖层厚3~5km,西部的合肥盆地下方,则达到4~7km。(2)剖面平均Moho面深度为30~32km左右,在郯庐断裂下方,Moho面深度在35km左右;在宁芜矿集区下方,Moho面整体深度偏浅,达30~31km左右,但局部范围内,Moho面深度至34km左右。(3)剖面的下地壳平均速度在6.5~6.6km/s左右,在宁芜矿集区下方,下地壳速度偏低,为6.4~6.5km/s左右。剖面上地幔顶部的速度结构平均在8.0~8.2km/s。在宁芜矿集区下方,速度偏低,为7.9~8.1km/s左右。(4)郯庐断裂带的下方,从地表开始,还存在20多千米长的低速异常带,一直延伸到Moho面附近。剖面的宁芜矿集区下方Moho面上隆、下地壳及上地幔的低速异常等壳幔结构特征,预示下地壳不以榴辉岩残体为主,支持燕山期地幔岩浆的上涌和侵入并成矿,是热上涌物质的源地。     

相位加权叠加方法在探测鄂尔多斯东南缘地壳结构中的应用

本文利用在鄂尔多斯东南缘地区宽频带流动地震台阵记录的远震数据,提取各台站的接收函数,并利用相位加权方 法进行单台多震叠加、H -κ叠加以及共转换点叠加,获得了研究区莫霍过渡带的深度及其变化趋势。研究结果显示,莫霍的 深度由鄂尔多斯块体往东南方向逐渐变浅,在不同区域莫霍具有不同的特征：鄂尔多斯的莫霍深度在42~38 km;渭河-山 西地堑的莫霍出现约3 km的上隆;熊耳-伏牛山的莫霍深度在35~33 km;河淮盆地的莫霍形态比较复杂。相位加权叠加方 法能有效地压制相关性不好的噪音,在部分受噪音及沉积层多次波干扰的台站记录中,对突出莫霍的转换波Ps震相有很大 的帮助。     

Lower lithospheric structure beneath the Trans-European Suture Zone from POLONAISE''97 seismic profiles

The large-scale POLONAISE'97 seismic experiment investigated the velocity structure of the lithosphere in the Trans-European Suture Zone (TESZ) region between the Precambrian East European Craton (EEC) and Palaeozoic Platform (PP). In the area of the Polish Basin, the P-wave velocity is very low (Vp <6.1 km/s) down to depths of 15–20 km, and the consolidated basement (Vp5.7–5.8 km/s) is 5–12 km deep. The thickness of the crust is 30 km beneath the Palaeozoic Platform, 40–45 km beneath the TESZ, and 40–50 km beneath the EEC. The compressional wave velocity of the sub-Moho mantle is >8.25 km/s in the Palaeozoic Platform and 8.1 km/s in the Precambrian Platform. Good quality record sections were obtained to the longest offsets of about 600 km from the shot points, with clear first arrivals and later phases of waves reflected/refracted in the lower lithosphere. Two-dimensional interpretation of the reversed system of travel times constrains a series of reflectors in the depth range of 50–90 km. A seismic reflector appears as a general feature at around 10 km depth below Moho in the area, independent of the actual depth to the Moho and sub-Moho seismic velocity. “Ringing reflections” are explained by relatively small-scale heterogeneities beneath the depth interval from 90 to 110 km. Qualitative interpretation of the observed wave field shows a differentiation of the reflectivity in the lower lithosphere. The seismic reflectivity of the uppermost mantle is stronger beneath the Palaeozoic Platform and TESZ than the East European Platform. The deepest interpreted seismic reflector with zone of high reflectivity may mark a change in upper mantle structure from an upper zone characterised by seismic scatterers of small vertical dimension to a lower zone with vertically larger seismic scatterers, possible caused by inclusions of partial melt.     

Structure of the crust and upper mantle beneath the central european rift system

The crustal structure of the central European rift system has been investigated by seismic methods with varying success. Only a few investigations deal with the upper-mantle structure. Beneath the Rhinegraben the Moho is elevated, with a minimum depth of 25 km. Below the flanks it is a first-order discontinuity, while within the graben it is replaced by a transition zone with the strongest velocity gradient at 20–22 km depth. An anomalously high velocity of up to 8.6 km/s seems to exist within the underlying upper mantle at 40–50 km depth. A similar structure is also found beneath the Limagnegraben and the young volcanic zones within the Massif Central of France, but the velocity within the upper mantle at 40–50 km depth seems to be slightly lower. Here, the total crustal thickness reaches only 25 km. The crystalline crust becomes extremely thin beneath the southern Rhônegraben, where the sediments reach a thickness of about 10 km while the Moho is found at 24 km depth. The pronounced crustal thinning does not continue along the entire graben system. North of the Rhinegraben in particular the typical graben structure is interrupted by the Rhenohercynian zone with a “normal” West-European crust of 30 km thickness evident beneath the north-trending Hessische Senke. A single-ended profile again indicates a graben-like crustal structure west of the Leinegraben north of the Rhenohercynian zone. No details are available for the North German Plain where the central European rift system disappears beneath a sedimentary sequence of more than 10 km thickness.     

Crustal velocity structure beneath the western Andes of Colombian using receiver-function inversion

Analysis of teleseismic records obtained in two broadband seismic stations of three components located on the Andean region of Colombia is presented in this work. The two stations are located at the Western Cordillera (WC), station BOL, and at the Central Cordillera (CC), station PBLA. The analysis of seismograms was performed by inversion of the receiver functions (RF) in order to obtain the crustal velocity structure beneath the receivers. The receiver function is a spectral ratio obtained from teleseismic earthquakes recorded by broadband seismic stations, which allows the calculation of the velocity structure beneath the receiver by removing source effects in the horizontal components of the seismic traces. Data stacking was performed in order to improve signal to noise ratio and then the data was inverted by using two optimization algorithms: a genetic algorithm (GA), and a simulated annealing algorithm (SA). The present work calculates the receiver functions using teleseismic earthquakes at epicentral distances (Δ) ranging between 30° and 90° and recorded at the two stations within the years 2007 and 2009.Delay times between P and PS waves converted at the Moho boundary were used to constrain the velocity structure. The receiver functions at the stations were generated from seismic events within a broad range of back azimuth. Data from gravity and magnetism were also used during the geophysical survey. The depth of the Moho boundary was found to be at 40 km in the WC beneath station BOL and at 43 km in the CC beneath station PBLA. The upper crust, with a thickness of 5 km, is characterized by a shear wave velocity of about 3.0 km s⁻¹; the shallower layers, at approximately 1.0 km, have shear wave velocities between 2.2 and 2.6 km s⁻¹, which corresponds to sediments overlying the upper crust. These observations support the hypothesis of a thickness of the crust at the root of the mountain range to be between 32 and 50 km. The calculated receiver functions were compared with artificial ones generated from the inversion of 48000 models of horizontal layers for each station using a GA and an SA that allowed a satisfactory coverage of all the sample space in order to avoid non-unique solutions. Beneath station BOL a moderate low-velocity zone (LVZ) was found, which was caused by accretionary processes of the ophiolite complex in the WC.     

多玛-德庆-达孜断面壳幔密度结构特征

利用人机交互重震联合反演的方法研究了多玛-德庆-达孜断面的二维壳幔横向密度结构特征。模拟结果显示,剖面下的地壳内部大部分存在低速层,念青唐古拉山两侧的德庆、羊八井附近存在两条深大正断层,切割并抬升了其下的中地壳低密度层,低密度层整体被向上抬升5～10 km,使得念青唐古拉山深部表现为一个地垒构造。念青唐古拉山位于莫霍面由浅变深的缓坡上,向东逐渐变深。软流圈在念青唐古拉山下形状发生变化,表现为“上凸”特征。     

Crustal shear-wave velocity structure beneath northeast India from teleseismic receiver function analysis

We investigated the seismic shear-wave velocity structure of the crust beneath nine broadband seismological stations of the Shillong–Mikir plateau and its adjoining region using teleseismic P-wave receiver function analysis. The inverted shear wave velocity models show ∼34–38 km thick crust beneath the Shillong Plateau which increases to ∼37–38 km beneath the Brahmaputra valley and ∼46–48 km beneath the Himalayan foredeep region. The gradual increase of crustal thickness from the Shillong Plateau to Himalayan foredeep region is consistent with the underthrusting of Indian Plate beyond the surface collision boundary. A strong azimuthal variation is observed beneath SHL station. The modeling of receiver functions of teleseismic earthquakes arriving the SHL station from NE backazimuth (BAZ) shows a high velocity zone within depth range 2–8 km along with a low velocity zone within ∼8–13 km. In contrast, inversion of receiver functions from SE BAZ shows high velocity zone in the upper crust within depth range ∼10–18 km and low velocity zone within ∼18–36 km. The critical examination of ray piercing points at the depth of Moho shows that the rays from SE BAZ pierce mostly the southeast part of the plateau near Dauki fault zone. This observation suggests the effect of underthrusting Bengal sediments and the underlying oceanic crust in the south of the plateau facilitated by the EW-NE striking Dauki fault dipping 30⁰ toward northwest.     

Moho depth variation beneath southwestern Japan revealed from the velocity structure based on receiver function inversion

The Philippine Sea plate is subducting under the Eurasian plate beneath the Chugoku-Shikoku region, southwestern Japan. We have constructed depth contours for the continental and oceanic Mohos derived from the velocity structure based on receiver function inversion. Receiver functions were calculated using teleseismic waveforms recorded by the high-density seismograph network in southwestern Japan. In order to determine crustal velocity structure, we first improved the linearized time-domain receiver function inversion method. The continental Moho is relatively shallow ( 30 km) at the coastline of the Sea of Japan and at the Seto Inland Sea, and becomes deeper–greater than 40 km–around 35°N and 133.8°E. Near the Seto Inland Sea, a low-velocity layer of thickness 10 km lies under the continental Moho. This low-velocity layer corresponds to the subducting oceanic crust of the Philippine Sea plate. The oceanic Moho continues to descend from south to northwest and exhibits complicated ridge and valley features. The oceanic Moho runs around 25 km beneath the Pacific coast and 45 km beneath the Seto Inland Sea, and it extends to at least to 34.5°N. The depth variation of the Moho discontinuities is in good qualitative agreement with the concept of isostasy. From the configurations of both the continental and oceanic Mohos, we demonstrate that the continental lower crust and the subducting oceanic crust overlap beneath the southern and central part of Shikoku and that a mantle wedge may exist beneath the western and eastern part of Shikoku. The southern edge of the overlapping region coincides with the downdip limit of the slip area of a megathrust earthquake.     

Mohorovičić discontinuity beneath Fennoscandia and adjacent parts of the Norwegian Sea and the North Sea

A preliminary contour map showing the Mohorovičić discontinuity (Moho) beneath Fennoscandia, adjacent parts of the Norwegian Sea and the North Sea has been compiled on the basis of published information from deep seismic soundings.The Moho contour map shows a 10 km thick crust beneath the investigated basin-region of the Norwegian Sea. It seems that the Vøring Plateau has at least in part a continental structure even if the Moho-depth is only 15 km. A shallow Moho (28–30 km) all along the Norwegian coast is a well established feature. A good correlation between the surface elevation of the mountain range running through Norway and parts of Sweden and the depth of the Moho is also well established. The Gulf of Bothnia is a region of a great Mono-depression.