http://www.sciencedirect.com/science/article/pii/S1674987113001369

The 3-D P- and S-wave velocity models of the upper crust beneath Southwest Iberia are determined by inverting arrival time data from local earthquakes using a seismic tomo~raphy method. We used a total of 3085 P- and 2780 S-wave high quality arrival times from 886 local earthquakes recorded by a per- manent seismic network, which is operated by the Institute of Meteorology （IM）, Lisbon, Portugal. The computed P- and S-wave velocities are used to determine the 3-D distributions of Vp/Vs ratio. The 3-D velocity and Vp/Vs ratio images display clear lateral heterogeneities in the study area. Significant veloc- ity variations up to ~6% are revealed in the upper crust beneath Southwest lberia, At 4 km depth, both P- and S-wave velocity take average to high values relative to the initial velocity model, while at 12 km, low P-wave velocities are clearly visible along the coast and in the southern parts. High S-wave velocities at 12 km depth are imaged in the central parts, and average values along the coast; although some scattered patches of low and high S-wave velocities are also revealed. The Vp/Vs rztio is generally high at depths of 4 and 12 km along the coastal parts with some regions of high Vp/Vs ratio in the north at 4 km depth, and low Vp/Vs ratio in the central southern parts at a depth of 12 km, The imaged low velocity and high Vp/Vs ratios are related to the thick saturated and unconsolidated sediments covering the region; whereas the high velocity regions are generally associated with the Mesozoic basement rocks.     

准噶尔盆地东部构造特征及演化定量分析

准噶尔盆地东部地区经历了多期次的构造运动,其构造特征和形成演化机制对该地区的油气勘探和开发具有十分重要的指导意义。运用高分辨率的二维、三维地震、测井数据,优选十条地质格架剖面开展精细构造解释,刻画出不同构造单元的地质结构特征,建立了跨各个构造单元的地质解译模型。在精细构造解译的基础上,基于平衡剖面恢复原理,通过Midland Valley的3D MOVE功能模块对10条地质格架剖面进行构造恢复,并对其各地质时期构造缩短量和缩短速率进行定量表征。准噶尔东部地区缩短量及缩短速率统计分析表明,在东西方向上,三叠纪至侏罗纪缩短量（4.60~11.28 km）及缩短速率最大（0.12~0.20 mm/a）,这一时期准东地区经历了强烈的东西向挤压构造变形;在南北方向上,二叠纪和新近纪末期缩短量（2.56~8.93 km、0.54~6.90 km）及缩短速率最大（0.05~0.15 mm/a、0.02~0.19 mm/a）,这两个时期准东地区经历了强烈的南北向挤压构造变形。      

Crustal and upper mantle seismic structure of the Australian Plate, South Island, New Zealand

Seismic reflection and refraction data were collected west of New Zealand's South Island parallel to the Pacific–Australian Plate boundary. The obliquely convergent plate boundary is marked at the surface by the Alpine Fault, which juxtaposes continental crust of each plate. The data are used to study the crustal and uppermost mantle structure and provide a link between other seismic transects which cross the plate boundary. Arrival times of wide-angle reflected and refracted events from 13 recording stations are used to construct a 380-km long crustal velocity model. The model shows that, beneath a 2–4-km thick sedimentary veneer, the crust consists of two layers. The upper layer velocities increase from 5.4–5.9 km/s at the top of the layer to 6.3 km/s at the base of the layer. The base of the layer is mainly about 20 km deep but deepens to 25 km at its southern end. The lower layer velocities range from 6.3 to 7.1 km/s, and are commonly around 6.5 km/s at the top of the layer and 6.7 km/s at the base. Beneath the lower layer, the model has velocities of 8.2–8.5 km/s, typical of mantle material. The Mohorovicic discontinuity (Moho) therefore lies at the base of the second layer. It is at a depth of around 30 km but shallows over the south–central third of the profile to about 26 km, possibly associated with a southwest dipping detachment fault. The high, variable sub-Moho velocities of 8.2 km/s to 8.5 km/s are inferred to result from strong upper mantle anisotropy. Multichannel seismic reflection data cover about 220 km of the southern part of the modelled section. Beneath the well-layered Oligocene to recent sedimentary section, the crustal section is broadly divided into two zones, which correspond to the two layers of the velocity model. The upper layer (down to about 7–9 s two-way travel time) has few reflections. The lower layer (down to about 11 s two-way time) contains many strong, subparallel reflections. The base of this reflective zone is the Moho. Bi-vergent dipping reflective zones within this lower crustal layer are interpreted as interwedging structures common in areas of crustal shortening. These structures and the strong northeast dipping reflections beneath the Moho towards the north end of the (MCS) line are interpreted to be caused by Paleozoic north-dipping subduction and terrane collision at the margin of Gondwana. Deeper mantle reflections with variable dip are observed on the wide-angle gathers. Travel-time modelling of these events by ray-tracing through the established velocity model indicates depths of 50–110 km for these events. They show little coherence in dip and may be caused side-swipe from the adjacent crustal root under the Southern Alps or from the upper mantle density anomalies inferred from teleseismic data under the crustal root.     

3-D GRACE gravity model for the 2011 Japan earthquake

The GRACE mission has contributed to the seismic characterization of major earthquakes in offshore regions of the world. Here, we isolate satellite gravity signal (μGal range) for the Japan Earthquake of 2011 using a difference method. Contrary to the existing gravity models, we propose a unit vertical pyramid based five-layer 3-D thrust fault model, which extends to the hypocenter and honors the ocean water layer and sea floor upheaval also. Our model partly uses existing seismological information (hypocenter depth of 32 km, rupture length of 300 km and vertical slip of 4 m), provides a snapshot of episodic subduction of the Pacific Plate below the Atlantic Plate and its gravity response closely matches the observed gravity (RMS error of 3.4012×10^?13μGal), fully accounting for co-seismic mass redistribution including sea surface deformation. Our inferred rupture length, rupture velocity, average seismic moment magnitude and momentum, respectively, are 300 km, 4.49 km/s, 1.152×10²¹?1.8816×10²¹ N m and 2.319×10⁶ GNs, which fairly agree with the literature. Further, our model inferred momentum at the sea floor corresponds to an area pulse that led to Tsunami generation.     

http://www.sciencedirect.com/science/article/pii/S1674987111000417

The characteristics of the Bolokenu-Aqikekuduk (Bo-A) fault, a right-lateral strike-slip fault that runs for more than 700 km long and obliquely cuts North Tianshan Mountains, are evaluated here based on remote sensing data, and through an analysis of the results from field investigations as well as climate-geomorphic events. The fault is composed of a western segment with a NW strike and an eastern segment with a NWW strike. The western segment is nearly 250 km long, extending northwestward into Kazakhstan with a right-lateral strike-slip rate of 5 mm/a. This domain consists of 4e5 rupture sections, with 3e4 deformation belts, caused by ancient or historical earthquakes, and suggesting the potential for the occurrence of further strong earthquakes (with M z 7.5) in future. The eastern segment of the fault shows a right-lateral strike-slip rate of 1e1.4 mm/a, with the development of 3e4 deformation belts caused by ancient or historical earthquakes, and with a potential for future strong earthquake with M z 7.0. A typical strain partitioning style in the compression area has developed between the intermontane Bo- A fault and the piedmont thrust structures of Northern Tianshan Mountains, under the effect of oblique compression, as indicated by the piedmont thrust structure and the strike-slip fault in the mountains.     

Mapping the mantle lithosphere for diamond potential using teleseismic methods

Recent developments in seismic, magnetotelluric and geochemical analytical techniques have significantly increased our capacity to explore the mantle lithosphere to depths of several hundred kilometres, to map its structures, and through geological interpretations, to assess its potential as a diamond reservoir. Several independent teleseismic techniques provide a synergistic approach in which one technique compensates for inadequacies in another. Shear wave anisotropy and discontinuity studies using single seismic stations define vertical mantle stratigraphic columns. For example, beneath the central Slave craton seismic discontinuities at depths of 38, 110, 140 and 190 km appear to bound two distinct anisotropic layers. Tomographic (3-D) inversions of seismic wave travel-times and 2-D inversions of surface or scattered waves use arrays of stations and provide lateral coverage. In combination, and by correlation with electrical conductivity and xenolith petrology studies, these techniques provide maps of key physical properties within parts of the cratons known to host diamonds. Beneath the Slave craton, the discontinuity at 38 km is the base of the crust; the boundaries at 110 and 140 km appear to bound a layer of depleted harzburgite that is interpreted to contain graphite. To date, only some of these techniques have been applied to the Slave and Kaapvaal cratons so that the origin and geological history of the currently mapped mantle structures are not, as yet, generally agreed.     

vp/vs Estimation in Tibetan Crust From Inversion of Surface Wave Dispersions

v_p/v_s ESTIMATION IN TIBETAN CRUST FROM INVERSION OF SURFACE WAVE DISPERSIONS     

龙门山中段山前带浅层冲断系统的结构、形成与演化

本文依据断层相关褶皱几何学原理,对龙门山中段地震剖面进行了精细解释。研究发现,龙门山中段山前带浅层冲断系统存在多套滑脱层,具有上下分层变形特征。浅层滑脱层为上三叠统须家河组三段(T_3~x3)的碳质页岩夹煤层,其上发育双重构造和叠瓦构造;下三叠统嘉陵江组四、五段(T_1j~(4-5))的膏岩层,发育断层传播褶皱、冲起构造和构造楔;深层为下寒武统的泥页岩层,发育断层转折褶皱和滑脱褶皱。该区滑脱断层所控制的地层变形和缩短量各不相同,其中三叠系上统缩短量最大,大于30 km;三叠系下统至古生界地层缩短量约为14.5 km;侏罗系以上的地层缩短量则较小。研究区内的通济场断裂(F_3)为印支末期形成的一套逆冲断层组,其下部交于下寒武统滑脱层,深度约为10 km;关口断层(F_4)和彭县断裂(F_5)为晚侏罗世一早白垩世形成的逆冲断层,下部交与下三叠统嘉陵江组滑脱层,深度大约为8～10 km。这些断层以前展的方式破裂,并且长期活动。龙门山中段自中生代以来存在多期构造事件,主要发生诺利末期、印支晚幕、燕山期和喜马拉雅期。其中,燕山期和喜马拉雅期是龙门山活动最强烈的两个阶段,在龙门山中段山前带表现为大量断裂的长期活动,地壳缩短和龙门山快速隆升,并形成多种构造样式。     

http://www.sciencedirect.com/science/article/pii/S1674987112000849

New methods are presented for processing and interpretation of shallow marine differential magnetic data,including constructing maps of offshore total magnetic anomalies with an extremely high resolution of up to 1-2 nT,mapping weak anomalies of 5-10 nT caused by mineralization effects at the contacts of hydrocarbons with host rocks,estimating depths to upper and lower boundaries of anomalous magnetic sources,and estimating thickness of magnetic layers and boundaries of tectonic blocks. Horizontal dimensions of tectonic blocks in the so-called "seismic gap" region in the central Kuril Arc vary from 10 to 100 km,with typical dimensions of 25-30 km.The area of the "seismic gap" is a zone of intense tectonic activity and recent volcanism.Deep sources causing magnetic anomalies in the area are similar to the "magnetic belt" near Hokkaido. In the southern and central parts of Barents Sea,tectonic blocks with widths of 30-100 km,and upper and lower boundaries of magnetic layers ranging from depths of 10 to 5 km and 18 to 30 km are calculated.Models of the magnetic layer underlying the Mezen Basin in an inland part of the White Sea-Barents Sea paleorift indicate depths to the lower boundary of the layer of 12-30 km.Weak local magnetic anomalies of 2-5 nT in the northern and central Caspian Sea were identified using the new methods,and drilling confirms that the anomalies are related to concentrations of hydrocarbon.Two layers causing magnetic anomalies are identified in the northern Caspian Sea from magnetic anomaly spectra.The upper layer lies immediately beneath the sea bottom and the lower layer occurs at depths between 30-40 m and 150-200 m.     

塔里木盆地塔中低凸起滑脱构造与分层构造变形

塔中低凸起作为古生代形成的凸起,是油气运移聚集的有利指向区,研究其构造变形特征对油气勘探具有重要的意义。应用地震和钻井资料,在地震资料解释和分层构造复原基础上,研究认为：（1） 除塔中Ⅰ号断裂带部分段为基底卷入式外,塔中低凸起主要逆冲断裂以滑脱式为主,主逆冲断裂多在中、下寒武统膏盐层系滑脱;（2） 盐上地层变形特征与盐下地层变形特征不同,盐上地层构造变形强度总体上大于盐下地层构造变形强度;（3） 膏盐层系在分层构造变形过程中起到协调变形作用;（4） 塔中低凸起分层构造变形主要受控于俯冲造山及膏盐层系滑脱作用。     

http://www.sciencedirect.com/science/article/pii/S1674987111001289

The disastrous M_w 9.3(seismic moment 1.0×10³⁰ dyn/cm) earthquake that struck northwest Sumatra on 26 December 2004 and triggered～30 m high tsunami has rejuvenated the quest for identifying the forcing behind subduction related earthquakes around the world.Studies reveal that the strongest part（elastic core） of the oceanic lithosphere lie between 20 and 60 km depth beneath the upper （～7 km thick） crustal layer,and compressive stress of GPa order is required to fail the rock-layers within the core zone.Here we present evidences in favor of an intraplate origin of mega-earthquakes right within the strong core part（at the interface of semi-brittle and brittle zone）,and propose an alternate model exploring the flexing zone of the descending lithosphere as the nodal area for major stress accumulation. We believe that at high confining pressure and elevated temperature,unidirectional cyclic compressive stress loading in the flexing zone results in an increase of material yield strength through strain hardening, which transforms the rheology of the layer from semi-brittle to near-brittle state.The increased compressive stress field coupled with upward migration of the neutral surface（of zero stress fields） under noncoaxial deformation triggers shear crack.The growth of the shear crack is initially confined in the near-brittle domain,and propagates later through the more brittle crustal part of the descending oceanic lithosphere in the form of cataclastic failure.     

中阶构造煤等温吸附/解吸特征及机理

选择四个不同变形程度的中阶煤样品作为研究对象,通过开展煤样的等温CH4吸附/解吸实验、X射线衍射(XRD)和傅里叶变换红外光谱(FT-IR)测试分析,研究了构造煤等温吸附/解吸性随煤变形程度的演化特征及其地球化学机理.结果表明,构造煤等温CH4吸附和解吸曲线随压力升高均呈现先快速增大后逐渐稳定的变化趋势,符合I型等温线...     

Simulated annealing in 3-D seismic modelling and elastic structure of the mediterranean basin

3-D elastic structures images of the Mediterranean basin are obtained by solving a tomographic problem by means of a simulated annealing algorithm. The database consists of local Rayleigh wave group velocities determined for the fundamental mode in the 10–90s period range. These local velocities were obtained from surface wavetrains recorded at very broad band stations of MEDNET network. From a methodological point of view, the characteristics of the annealing algorithm and the amount of time required for computation suggest the implementation of parallel computational procedures to shorten the computational time. According to the thermodynamic analogies used in the annealing algorithm, we propose an alternative procedure to estimate uncertainties and correlations for variables defining the elastic model (shear velocities and layer thicknesses) without necessity of computing partial derivatives. From an applied point of view, the 3-D elastic model obtained shows, as main results, relevant differences for the eastern and western pans of the Mediterranean basin, specially down to 60 km. The changes in the position of the top and bottom asthenosphere surfaces can also be followed throughout the Mediterranean basin; remarkably, these changes are in agreement with some tectonic features.     

松辽盆地北部油田精细构造识别和应用

精细构造研究是随着高分辨率开发地震技术和油田的深度开采而产生的。由构造应力作用形成的微幅度构造、以沉积作用为主形成的储层微型构造，都属于精细构造的研究范畴，但二者在成因、识别方法上有所差异。大庆油田在高含水开发后期，利用高分辨率三维开发地震技术，对微幅度构造进行研究；进而在地震剖面上，识别出以前不识别的微幅度构造，尤其是通过滑动相关、倾角扫描和关联维等方法识别井间小断层；利用测井资料，研究储层微型构造，又通过微型构造图和趋势面剩余分析方法，通过对单层的层面起状程度和形态。这些对打井找油和剩余油研究都具有重要意义。     

2-D seismic tomographic and ray tracing modelling of the crustal structure across the Sudetes Mountains basing on SUDETES 2003 experiment data

The seismic data obtained during SUDETES 2003 experiment are analysed, and detailed crustal structure for profiles S02, S03 and S06 is presented using three different 2-D techniques: (1) “smooth” tomography of refracted waves travel times, (2) ray tracing of reflected and refracted waves, and (3) joint velocity and depth of reflector tomographic inversion. In spite of different interpretation techniques used, the models of the crustal structure show common characteristic features. The low velocity (V_p < 4 km/s) sedimentary layer was documented in the northeastern part of the study area. The topmost basement has in general a velocity of 5.8–6.0 km/s, and velocities at ca. 20 km depth are 6.15–6.25 km/s. The strong reflecting boundaries were found at 20–23 and 25–28 km depth with a velocity contrast about 0.4 km/s, and the highest velocities in the lowermost crust are 6.8–7.2 km/s. In general, the crust of the Bohemian Massif is slightly thicker (33–35 km) than in the northern part of the area. Velocities beneath Moho are relatively low, of 7.95 km/s. On the basis of well recorded reflected waves, mantle reflectors were discovered in the depth interval ca. 40–70 km. Apart of new results for the geology and tectonics of the area, some conclusion could be made about different techniques used. In the 2-D case the “clasical” ray tracing method with using all correlated phases gives the most adequate model of the structure, because of full, manual control of the model creation. The “smooth” first arrival travel times tomography, although very fast, is not satisfactory enough to describe the complex structure. So, the best candidate in 3-D case seems to be travel time tomography for both refracted and reflected waves in multi-layers models.     

华北地块南部巨型陆内俯冲带与秦岭造山带岩石圈现今三维结构

豫西横穿秦岭造山带的反射地震为主的综合地球物理探测，发现秦岭现今北界存在华北地块南部自北向南向秦岭的巨型陆内俯冲带，深达Ｍｏｈｏ面以下，与之相伴而生，在中上地壳发育自南向北的逆冲推构造带，千公里东西向延伸，主要发生于晚白垩世１００Ｍａ±，成为秦岭与华北地区块间中新生代重要陆内构造，它是秦岭造山带岩石圈现今三维结构的基本要素和组成部分，秦岭造山带岩石圈现今结构具有流变学分层的“立交桥”三维结构框架模型。显然它们具有统一的动力学背景，是秦岭造山带现今处于印度－青藏、太平洋和欧亚板块的西伯利亚地块等三大构造动力学体系复合部位，导致其从深部地幔动力学的最新调整到上部地壳响应所发生的壳幔等圈层相互作用的综合产物，可能是大陆长期保存、演化的主要途径与形式之一，具有重要的大陆动力学意义，对中国大陆构造、灾害、环境研究也具重要意义。     

南天山库车秋里塔格褶皱带三维构造分析

笔者利用库车秋里塔格地区3000km的二维地震反射资料，结合地表构造测量成果，分段叙述秋里塔格褶皱带的构造几何学和运动学性质，说明构造交汇部位断层和褶皱的叠加过渡关系，并通过二维构造剖面的组合，建立秋里塔格褶皱带的三维构造几何模型。研究发现秋里塔格褶皱带为浅部断层传播褶皱与深部断层转折褶皱叠加形成的复合型背斜带，深部台阶状逆断层的叠加作用、叠加断层位移量的转换、断层断坡高度的变化造成地表背斜沿走向发生变化，笔者通过测量断层叠加方式、断层位移量转换、断层断坡高度，说明秋里塔格褶皱带背斜叠加、扭曲、分叉现象的构造机理，并且给出了秋里塔格褶皱带断层的滑移量。     

巴东新城白土坡深层岩体软弱夹层地质特征

巴东组第三段中的软弱夹层是白土坡斜坡的主要结构面,巴东新城白土坡深层变形监测钻孔揭露白土坡斜坡巴东组第三段厚度在270m左右,主要贯通性软弱夹层有13层,为泥质灰岩碎块石夹土、黄褐色碎石土,中上部夹层分布较密,软弱夹层的空间分布由沉积环境所决定的岩性变化控制,典型夹层露头构造分析表明夹层由于构造作用发生过层间错动,夹层的存在有利于斜坡深层变形,三峡水库蓄水后水位的抬高将会影响到斜坡岩体的深层蠕变。     

2018年5月28日中国吉林松原M5.7级地震引起的液化构造*

2018年5月28日,吉林松原市宁江区毛都站镇牙木吐村发生M5.7级地震(45°16'12″N,124°42'35″E),震源深度13 km,震中位于郯庐断裂带西北侧的扶余/松原—肇东断裂带、第二松花江断裂带和扶余北断裂带交汇处。地震诱发震中距3 km范围内普遍的液化和地表裂缝,给当地居民带来严重灾害。可见液化构造以砂火山为主,其次为液化砂堆、液化砂脉和液化砂席等。液化砂火山又可分为有火山口型砂火山、无火山口型砂火山和无砂型(水)火山。地震液化伴生软沉积物变形构造有变形层理、负载构造和火焰构造、滑塌褶皱、碟状构造和包卷层理等。地震诱发液化砂火山形成过程包括液化层内超孔隙流体压力形成、上覆低渗透层破裂和水、砂喷出地表后砂涌3个阶段。液化和流化砂体在上涌过程中会注入低渗透黏土层形成各种形态的砂脉、砂席和多种类型的变形构造。垂向上地震液化结构可划分为底部松散可液化层、下部液化变形层、上部液化变形层和地表砂火山4层结构。液化层埋深2~5 m,液化层厚度2 m。松原M5.7级地震发震机制为NE-SW(35°~215°)方向挤压应力使断层活跃,推测扶余/松原—肇东断裂是主要的发震断层。松原地震液化构造研究为现代地震活动区和灾害易发区预测提供依据,为地震引发的现代软沉积物变形构造研究提供丰富的素材,兼具将今论古意义,为揭示本世纪以来郯庐断裂带北段进入了一个强断裂和地震活跃阶段提供了最新的实际资料。     

The crustal structure of the western Arabian platform from the spectral analysis of long-period P-wave amplitude ratios

The crustal structure of the western Arabian platform is derived using the spectral analysis of long-period P-wave amplitude ratios. The ratio of the vertical to the horizontal component is used to obtain the crustal transfer function based on thickness variations, crustal velocities, densities and the angle of emergence at the lower crust and upper mantle interface. Eleven well-defined earthquakes recorded at the long-period RYD station during the period from 1985 to 1994 were selected for analysis based on the following criteria: focal depths with a range between 7 and 89 km, body-wave magnitudes greater than 4.7, epicentral distances with a range from 8.8° to 26.5°, and back azimuthal coverage from 196° to 340°. Spectral analysis calculations were based on the comparison of the observed spectral ratios with those computed from theoretical P-wave motion obtained using the Thomson–Haskell matrix formulation for horizontally layered crustal models. The selection of the most suitable model was based on the identification of the theoretical model which exhibits the highest cross-correlation coefficient with the observed transfer function ratio. By comparing the spectral peak positions of the observed and theoretical values, the thickness and velocity can be resolved within 3 km and 1 km/s, respectively, of the observed values. The spectral analysis of long-period P-waves can detect a thin layer near the surface of about 1.6 km thick and a velocity contrast of about 10% with that of the underlying layer. A strong velocity gradient of about 0.05 km/s per km was found in the upper crust and 0.02 km/s per km in the lower crust. The derived crustal model is not unique due to the theoretical assumptions (horizontal layering, constant densities and velocities in each layer), quality of the data and complexities of the crustal structure. The crustal model suggests that the crust consists of five distinct layers. The upper crustal layer has a P-wave velocity of about 5.6 km/s and is about 1.6 km thick. The second layer has a velocity of about 6.2 km/s and is 10.2 km thick. The third layer shows a velocity of 6.6 km/s and is 6.8 km thick. The fourth layer has a velocity of about 6.8 km/s and is 12.3 km thick. The lower crustal layer has a velocity of about 7.5 km/s and is 9.3 km thick. The Mohorovicic discontinuity beneath the western Arabian platform indicates a velocity of 8.2 km/s of the upper mantle and 42 km depth.