The application of rapid potential field methods for the targeting of IOCG mineralisation based on physical property data,Great Bear magmatic zone,Canada

New techniques for the integration of gravity and aeromagnetic data through rock physical property relationships are tested for the rapid location of potential iron oxide–copper–gold (IOCG) exploration targets across the Great Bear magmatic zone (GBMZ). These techniques are based on the recognition of coincident or near-offset magnetic and gravity anomalies associated with IOCG deposits, resulting from their intense and combined iron-oxide and alkali alteration. In the GBMZ, the NICO (Au–Co–Bi–Cu) deposit is an atypical magnetite-group IOCG hosted within an intensely hydrothermally-altered metasedimentary sequence. Prospectivity maps for the NICO area are derived from the integration of high-resolution aeromagnetic and surface gravity data with physical property measurements of magnetic susceptibility and density. Method 1 combines the pseudo-gravity (derived from the aeromagnetic data) and Bouguer gravity data to determine the locations of superimposed high anomalies. Method 2 estimates the apparent susceptibility and density subsurface distribution based on vertical prism models of the magnetic and gravity data. The apparent susceptibility data are transformed to apparent density using physical property relationships. The two apparent density datasets are then combined to determine the location of coincident magnetic and gravity derived anomalies. The results of these methods are supported by, and compared with, similar prospectivity maps generated through weights of evidence techniques. At NICO, the prospectivity maps accurately locate the deposit and nearby occurrences. Despite the lower resolution of the regional gravity data, application of the techniques across the GBMZ is successful at locating mineralised IOCG systems including the magnetite-group systems at Grouard, Fab, DeVries and Cole Lake, the magnetite to hematite-group systems of the Port Radium-Echo Bay district, and has highlighted possible targets for future exploration.     

Crustal Structure of Turkey from Aeromagnetic, Gravity and Deep Seismic Reflection Data

In this paper, aeromagnetic and gravity anomalies obtained from the General Directorate of Mineral Research and Exploration were subjected to upward continuation to 3?km from the ground surface to suppress shallow effects and to expose only regional, deep sources. Then, a reduction to pole (RTP) map of aeromagnetic anomalies was produced from the 3?km upward continued data. A sinuous boundary to the south of Turkey is observed in the RTP map that may indicate the suture zone between the Anatolides and African/Arabian Plates in the closure time of the Tethys Ocean. The sinuous boundary can be correlated with the recent palaeo-tectonic maps. The southern part of the sinuous boundary is quite different and less magnetic in comparison with the northern block. In addition, maxspots maps of the aeromagnetic and gravity anomalies were produced to find out and enhance the boundaries of tectonic units. Crustal thickness, recently calculated and mapped for the western Turkey, is also extended to the whole of Turkey, and the crustal thicknesses are correlated with the previous seismological findings and deep seismic sections. The average crustal thickness calculations using the gravity data are about 28?km along the coastal regions and increase up to 42?km through the Iranian border in the east of Turkey. Density and susceptibility values used as parameters for construction of two-dimensional (2D) gravity and magnetic models were compiled in a table from different localities of Turkey. 2D models indicate that all of the anomalous masses are located in the upper crust, and this could be well correlated with the earthquakes which occurred at shallow depths.     

内蒙古阴山地区特异区域重磁场与深部构造

根据内蒙古阴山山系及邻近地区的布格重力异常分布特征，发现阴山、大青山山地和呼包盆地地区的布格重力异常分布与地形高程呈“同步型”的特异变化特征.而该地区航磁异常分布呈现为阴山山区是大面积负磁异常区，呼包盆地为强正磁异常区的特异磁异常分布特征.通过对地震、大地电磁数据、特别是重力数据资料的处理分析，给出阴山山系和呼包盆地地区的地壳结构，均表明地壳底界面都没有明显的下凹与上凸，且盆地北缘为两大块体的接触带.这些特征可能表征着阴山山系和呼包盆地重磁异常呈特异变化的一些原因.     

北部海岸带(台州以北)航磁异常特征及断裂划分

为满足中国海岸带海陆统筹调查的需求,基于最新编制的中国北部海岸带(台州以北)1:50万航磁图件,利用逐点化极、延拓、垂向导数等数据位场转化处理,结合地质背景、物性资料和已有航空物探解释成果,对研究区磁场特征进行分析,分区探讨航磁异常成因,并编制北部海岸带(台州以北)断裂分布图。结果表明,海岸带地区磁性较强的岩石广泛发育,以NE—NNE向为主的线性磁异常带是大量中新生代中酸性岩浆岩的反映,而区域性团块状磁异常或宽缓正负磁异常则为区域变质岩系的反映。研究区断裂发育,断裂展布方向基本以NE向、NNE向为主,NW向次之,其中深大断裂对区域构造、岩浆活动等有明显的控制作用。本研究编制的北部海岸带航磁"一张图"作为质量可靠的基础数据,可为解决海岸带基础环境和地质问题提供丰富的地球物理信息。依据航磁资料划分的断裂,解决了特殊地理环境下海陆断裂不衔接的问题,实现了断裂海陆统筹的目标,可为海陆交互区重大工程规划提供安全性评价依据。     

川西高原重磁异常特征与构造背景分析

川西高原位于青藏高原东缘,是我国大陆地壳构造变形及地震活动最强烈的区域.利用最新重力、航磁资料,通过异常分析和反演计算,研究了该区鲜水河断裂、理塘断裂、金沙江断裂的重磁异常特征、莫霍面特征、居里面特征,分析得出了这些断裂的深部地质结构与构造背景.计算表明:川西高原莫霍面东南浅、西北深,地壳厚度在43~63km之间.居里面特征表现为条带状,深度在17~23km之间.其中,鲜水河断裂带对应莫霍面深度梯度带,居里面为高低起伏圈闭.理塘断裂带北段莫霍面局部隆坳相间,南段莫霍面逐渐抬升,居里面呈现由西向东加深的梯度带.金沙江断裂带,居里面形成局部抬升,深部可能存在高温地热异常源.综合分析认为,川西高原地壳结构主要特点为:增厚的下地壳,热-塑性变形的中地壳,脆性变形的上地壳.     

A geophysical approach to the granite batholith under the eastern Southern Uplands,Scotland

From our interpretation of the Bouguer gravity and aeromagnetic anomalies in south-east Scotland, we conclude that a massive granite batholith underlies the greater part of the eastern Southern Uplands. The granite model which we computed earlier from gravity anomalies in the Tweeddale area fits the observed magnetic anomalies closely, if a normal magnetization of 0.095 A m^–1 is assigned, similar to values found for exposed local granites. Further gravity modelling shows that, apart from the Tweeddale boss, the granite shallows to less than 1 km near Lammer Law in East Lothian and extends north of the Lammermuir Fault. A model for the East Lothian volcanics was computed from their aeromagnetic anomalies, then their gravitational effect was combined with that estimated for the Devonian and Carboniferous sediments and the result stripped off the observed gravity field. The residual gravity anomalies were used to generate a two-dimensional model for the granite north of the Lammermuir Fault. The expected tectonic consequences of a massive granite batholith in the eastern Southern Uplands are compared with the known development of faults and sedimentary basins around its margins.     

山体遮挡对滇池风生流的影响初探

用二维风生流数值模型模拟滇池湖流运动。滇池在主导风向西南风作用下,假定湖面风场是均匀的,数值模拟的湖流流态与实测湖流结果相差很大。而考虑山体遮挡影响,根据实测湖流期间现有的风情资料,在湖面上构造一非均匀风场,数值模拟结果与实测值基本一致。山体遮挡对滇池风生流的影响是不容忽视的。建议进一步进行湖流和湖面风向、风速监测,并建立过山气流数学模型,深入研究山体遮挡对湖泊风生流的影响。     

综合地球物理方法在华南桂中海相残留盆地沉积相预测中的应用

沉积相研究是盆地隐蔽油气藏勘探中重要的研究内容之一,综合利用地球物理方法有效识别构造、岩性或沉积相差异是盆地隐蔽油气藏勘探的前提.本文基于重力、航磁、地震等综合地球物理资料,通过重磁异常正演剥离和剖面正反演拟合技术研究了华南桂中地区海相地层的密度分布特征,预测了岩相、沉积相的变化规律.研究发现,本区中、下泥盆统海相地层存在横向的岩性、岩相变化,研究区西北、东南部的台地相区重力异常高、岩石拟合密度值高;中部“X”型台地边缘相区重力异常杂乱、岩石拟合密度变化范围大;东部台沟相区重力异常低、岩石拟合密度值低.利用综合地球物理方法预测沉积相为盆地岩性圈闭油气藏和生物礁油气藏勘探提供了新的研究思路,研究成果已得到初步检验,但还有待进一步完善与实践.     

攀西地区重力场特征及地壳密度结构

攀西地区位于峨眉山大火成岩省中西部,构造和岩浆特征显著,地震活动强烈.通过对野外重力测量得到的云县—会东和普洱—七甸两条剖面的高精度重力观测数据进行处理和分析,构建了沿剖面的二维地壳密度结构,其中普洱—七甸剖面与孟连—马龙宽角地震剖面部分位置重合.同时结合区域重力异常特征及下地壳视密度填图结果,得到如下初步认识:红河断裂带是南北地震带南段地区重要的构造分界线,断裂带南北向密度结构和莫霍面分布形态存在较大差异,沿走向构造变化.云县—会东剖面上大姚—会东段下地壳底部存在密度较高的壳幔过渡层,结合研究区下地壳底部壳幔过渡层的密度分布特征,认为该过渡层不是攀西裂谷下的"裂谷垫",而是由岩浆底侵作用造成的.     

Regional metallogenic structure based on aeromagnetic data in northern Chile

Chile is a very important country that forms part of the Andean metallogenic belts. The Atacama and Domeyko fault systems in northern Chile control the tectonic–magmatic activities that migrate eastward and the types of mineral resources. In this paper, we processed and interpreted aeromagnetic data from northern Chile using reduction to pole, upward field continuation, the second derivative calculation in the vertical direction, inclination angle calculation, and analytical signal amplitude analysis. We revealed the locations and planar distribution characteristics of the regional deep faults along the NNE and NS directions. Furthermore, we observed that the major reasons for the formation of the tectonic–magmatic rocks belts were the nearly parallel deep faults distributed from west to east and multiple magmatic activities along these faults. We ascertained the locations of volcanic mechanisms and the relationships between them using these regional deep faults. We deduced the spatial distributions of the basic–intermediate, basic, and acidic igneous rocks, intrusive rocks, and sedimentary sequences. We showed the linear positive magnetic anomalies and magnetic anomaly gradient zones by slowly varying the background, negative magnetic anomaly field, which indicated the presence of strong magmatic activities in these regional deep faults; it also revealed the favorable areas of copper and polymetallic mineralization. This study provides some basic information for further research on the geology, structural characteristics, and mineral resource prospecting in northern Chile.     

龙门山断裂带地壳结构的三维建模

为了实现龙门山区域地质信息的科学管理与共享,推动该区域地球物理资料的统一管理,本文在整理现有二维地球物理探测数据的基础上构造了龙门山断裂带区域的三维地壳结构模型,并结合实测的布格重力异常数据对模型进行了分析。结果表明,地层模型正演的整体重力场与实测布格重力异常基本吻合,初步证明该模型的正确性。局部重力场显示:在该模型的尺度下,沉积层对整体重力场的变化贡献较小;中上地壳有不同程度的隆起和坳陷,与前人研究所揭示的低速异常体吻合;地幔表现为规则的自西北至东南单调上升的重力异常梯度带,与前人反演结果的趋势一致,从而证明了模型的可靠性。最后在重力资料约束下对模型进行了反演,进一步修正了模型。      

Structural origin of Lake Singkarak in central Sumatra

Since long it has been accepted that Lake Singkarak in Central Sumatra is nothing else but a remnant of a gigantic volcano — the Singkarak volcano — which once blew off its top to form a lake. Van Bemmelen, though not referring to Singkarak lake especially, explained the numerous depressions in Sumatra as the combined result of volcanic and tectonic activities, a phenomenon he called volcano-tectonic process which caused the formation of the socalled volcano-tectonic depressions. A short visit to the lake area in the months of February and March (1970) convinced the author that Lake Singkarak is neither a volcanic ruin nor a volcano-tectonic depression in the sense of van Bemmelen. Faulting evidences, morphology and the position of the Singkarak trough plus the distribution of volcanic products north and south of the lake led to the conclusion that the Singkarak trough is a depression making part of the 1650 km graben zone which stretches from Sumatra’s northern tip untill the Semangko valley in the SE. Field evidences suggest that the lake results from a damming process by volcanic material produced by the Marapi-Singgalang-Tandikat volcanoes in the north and by the products from the Talang volcano in the south.     

A new model of back-arc spreading in the Parece Vela Basin, northwest Pacific margin

Abstract Swath bathymetric data, single-channel seismic reflection profiles, magnetic and gravity anomalies in the northern part of the Parece Vela (West Mariana) Basin were obtained by comprehensive surveys conducted by the Hydrographic Department of Japan. The central zone of the Parece Vela Basin is characterized by the north-south trending chain of depressions in a right-stepping en echelon alignment. The morphology of these depressions is diamond shaped and bordered by steep escarpments of 1000-1500 m relative height. These fault escarpments extend northeastward and southwestward from the depressions into the surrounding basin floor and then gradually fade out. These escarpments have an S-shaped trend, and their geometry seems to be symmetric about the depressions. Minor ridges and troughs trending orthogonal to these escarpments are recognized. It is concluded that these depressions and escarpments are the topographic expression of extinct spreading axes and S-shaped transform faults, respectively. The age of the central depressions seems to be young, although details of tectonic processes forming them remains unsolved. The western province of the basin floor and basement is extremely rugged and characterized by minor ridges and troughs trending in a north-south direction. Although magnetic anomalies of the basin are very weak, magnetic lineations trending parallel to the topographic trend are recognizable in the central and western parts of the basin. Based on updated geomorpholog-ical features and magnetic anomalies revealed by the present survey, together with the previously published data including drilling results, it is proposed that the evolution of Parece Vela Basin took place in four stages of opening and tectonic activity: rifting, east-west spreading, northeast-southwest spreading with counter-clockwise rotation of spreading axes, and post-spreading deformation and volcanism. This proposed spreading model of the Parece Vela Basin is similar to that of the adjacent Shikoku Basin. The spreading axes of both basins were segmented and gradually rotated counter-clockwise in a later phase of the basin evolution, after the cessation of relatively uniform spreading nearly in an east-west direction.     

渭河盆地及邻区重力异常小波多尺度分解与解释

基于EGM2008重力场模型计算获得了渭河盆地及邻区布格重力异常。采用小波多尺度分解方法对布格重力异常进行了4阶小波逼近和小波细节分解,同时基于平均径向对数功率谱方法定量化地计算出1~4阶小波细节和小波逼近所对应的场源平均埋深。结合区域地质和地震资料,对获得的重力场结果进行分析,得到如下结论:①鄂尔多斯地块、渭河盆地、秦岭造山带3个一级构造单元的布格重力异常之间存在明显差异;构造区内部重力异常也存在横向的显著差异。布格重力异常的走向、规模、分布特征与二级构造区及主要的断裂具有一定的对应关系。②渭河盆地及邻区布格重力异常1~4阶细节对应4~23 km不同深度的场源信息,鄂尔多斯地块南缘东、西部的地壳结构存在明显的差异;渭河盆地凹陷、凸起构造区边界清晰,断裂边界与重力异常边界具有较好的一致性;秦岭造山带重力异常连贯性不好,东、西部重力异常变化特征表现出明显的差异。③渭河盆地及邻区布格重力异常分布与莫霍面埋深具有非常明显的镜像关系。渭河盆地及邻区地震主要分布在六盘山—陇县—宝鸡断裂带、渭河断裂与渭南塬前断裂交汇处、韩城断裂与双泉—临猗断裂交汇处。渭河盆地及邻区重力异常主要由中上地壳剩余密度体所影响,这可能是该区地震以浅源地震为主的主要原因。     

Ice cover,landscape setting,and geological framework of Lake Vostok,East Antarctica

Lake Vostok, located beneath more than 4 km of ice in the middle of East Antarctica, is a unique subglacial habitat and may contain microorganisms with distinct adaptations to such an extreme environment. Melting and freezing at the base of the ice sheet, which slowly flows across the lake, controls the flux of water, biota and sediment particles through the lake. The influx of thermal energy, however, is limited to contributions from below. Thus the geological origin of Lake Vostok is a critical boundary condition for the subglacial ecosystem. We present the first comprehensive maps of ice surface, ice thickness and subglacial topography around Lake Vostok. The ice flow across the lake and the landscape setting are closely linked to the geological origin of Lake Vostok. Our data show that Lake Vostok is located along a major geological boundary. Magnetic and gravity data are distinct east and west of the lake, as is the roughness of the subglacial topography. The physiographic setting of the lake has important consequences for the ice flow and thus the melting and freezing pattern and the lake’s circulation. Lake Vostok is a tectonically controlled subglacial lake. The tectonic processes provided the space for a unique habitat and recent minor tectonic activity could have the potential to introduce small, but significant amounts of thermal energy into the lake.     

Investigation into the regional wrench tectonics of inner East Anatolia (Turkey) using potential field data

The residual aeromagnetic and gravity anomalies of inner East Anatolia, surveyed by the Mineral Research and Exploration (MTA) of Turkey, display complexities. Some faults, which are known and new lineaments, are drawn from maxspot map derived from the location of the horizontal gradient of gravity anomalies. Tectonic lineaments of inner East Anatolia exhibit similarities to the direction of East Anatolian Fault Zone. Anticlockwise rotation, approximately −30°, defined from disorientations of aeromagnetic anomalies. The lineaments obtained from maxspots map produced from the gravity anomalies and disoriented aeromagnetic anomalies are in-line with the mobilistic system revealed by the palaeomagnetic data. These Alpine age continental rotations caused westward wrenching of the global lithosphere and led to significant tectonic reactivation and deformations. GPS measurements, current tectonic knowledge and the results of the evaluation of potential field data were combined in a base map to demonstrate similarities.     

汶川MW7.9地震周边地区布格重力异常与岩石圈垂向构造应力场

前人研究给出, 龙门山断裂带中南段地壳均衡异常显著, 具有发生7级以上大地震的深部动力背景。 2016年6月, 我们围绕该均衡异常显著区域开展重力/GNSS加密观测, 提高了该地区布格重力异常和地壳均衡异常场的空间分辨率。 依据上述观测结果与前期同类观测数据, 反演了汶川M_W7.9地震周边地区地壳密度构造。 结果显示, 龙门山断裂带是地壳密度变化的高梯度带, 其东侧地壳较薄, 但其西部明显变厚, 上、 中、 下地壳变化趋势均呈现上述特征; 研究区东侧的莫霍面深度为35~40 km, 西侧为60~65 km。 此外, 利用重力/GNSS联合观测数据计算了汶川M_W7.9地震震中区周边地区岩石圈承载的垂向构造应力场, 结果表明, 汶川M_W7.9地震震中区北部、 宁强、 峨眉山周边地区蓄积了-30 MPa至-40 MPa的负向构造应力, 龙门山断裂带中南段蓄积了约40 MPa的正向构造应力, 区域最大垂向构造应力分布在龙门山断裂带中南段, 临近芦山M_W6.6地震。 统计结果表明, 地震多发生在垂向构造应力高梯度带附近, 或垂向构造应力的高值区域。     

Crustal thickness beneath the Tanlu fault zone and its tectonic significance based on two-layer H-κ stacking

Tanlu fault zone(TLFZ)is the largest active fault zone in eastern China.It is characterized by complex tectonic evolution and multiple faults and marks the boundary between the North and South China blocks.An in-depth understanding of the distinct crustal structures of both parts of the TLFZ will provide valuable insights into the lithospheric and crustal thinning in eastern China,extensive magmatism since the Mesozoic,and formation mechanisms of metallogenic belts along the Yangtze River.In this study,a two-layer H-κ stacking approach was adopted to estimate the thicknesses of the sediment and crystalline crust as well as the corresponding vp/vs ratios based on high-quality teleseismic P-wave receiver functions recorded by permanent and temporary stations in and around the TLFZ.The geological units in the study region were delineated,especially the crustal structures beneath extensive sedimentary basins on both sides of the TLFZ.The following conclusions can be drawn:(1)The crustal thickness in and around the TLFZ greatly varies depending on the segment.In the northern segment,the crust is relatively thin beneath the eastern part of the Songliao Basin,a broad uplift of the Moho can be observed,and the Moho descends from south to north.The crust below the central and southern segments becomes thinner from west to east.The thickness of the crust is less than 30 km toward the eastern side of the boundary between the Jiangsu and Anhui provinces,that is,significantly thinner than in other areas.In terms of the vp/vs ratios,high anomalies were detected in the central-southern segments of the TLFZ,indicating the upwelling of deep mantle magma via deep faults.(2)Positive isostatic gravity anomalies were observed in the eastern part of the northern segment of the TLFZ and in the eastern part of the Suwan segment.The crustal thickness is smaller than that obtained from the Airy model of isostasy.This suggests that the lower crust in this area may have experienced intensive transformation processes,which may be related to crustal thinning(caused by crustal extension)and the strong uplift of the mantle in eastern China.The isostatic gravity anomalies between the eastern and western parts of the TLFZ indicate that the fault zone plays a dominant role in controlling the development of the deep crustal structure.(3)Significant crustal thinning was observed beneath the eastern part of the boundary between the Jiangsu and Anhui provinces in the southern segment of the TLFZ,suggesting that this area is prone to lithospheric thinning of the North China Craton.Due to the subduction,compression,and retreat of the Paleo-Pacific Plate during the Yanshanian Period as well as the dehydration of subducting oceanic crust(within subduction zones),the asthenosphere and oceanic crust in eastern China partially melted,resulting in mantle enrichment.The basic magma from the mantle is accumulated at the base of the crust,leading to magmatic underplating.In areas with weak topography toward the east of the TLFZ,magma rises to the upper crust and surface,resulting in the enrichment of multiple'metal deposits in this area.     

A distinction technique between volcanic and tectonic depression structures based on the restoration modeling of gravity anomaly: a case study of the Hohi volcanic zone, central Kyushu, Japan

In this study, we propose a numerical modeling technique which restores the gravity anomaly of tectonic origin and identifies the gravity low of caldera origin. The identification is performed just by comparing the restored gravity anomalies with the observed gravity anomalies, thus we do not need detailed geophysical and geological information around the buried caldera. The technique has been successfully applied to distinguish the gravity low originated in the buried Shishimuta caldera from other gravity lows in the Hohi volcanic zone, central Kyushu in Japan.     

THE 3-D VELOCITY STRUCTURE OF CRUST AND UPPERMOST MANTLE AND ITS TECTONIC IMPLICATIONS IN FUJIAN PROVINCE

It is important to detect the fine velocity structures of the crust and uppermost mantle to understand the regional tectonic evolution, earthquake generation processes, and to conduct earthquake risk assessment. The inversion of uppermost mantle velocity and Moho depth are strongly influenced by crustal velocity heterogeneity. In this study, we collected first arrivals of Pg and Pn and secondary arrivals of Pg wave from the seismograms recorded at Fujian provincial seismic network stations. New 3-D P-wave velocities were inverted by multi-phase joint inversion method in Fujian Province. Our results show that the fault zones in Fujian Province have various velocity patterns. The shallow crust is characterized by high velocity that represents mountains, while the mid-lower crust shows low velocities. The anomalous velocities are correlated closely with tectonic faults in Fujian Province. Velocity anomalies mainly show NE-trending distribution, especially in the mid-lower crust and uppermost mantle, which is consistent with the NE-trending of the regional main fault zones. Meanwhile, a part of velocity patterns show NW trending, which is related to the secondary NW-oriented faults. Such velocity distribution also shows a geological structural pattern of "zoning in east-west direction and blocking in north-south direction" in Fujian area. In the crust, a low velocity zone is found along Zhenghe-Dapu fault zone as mentioned by previous study, however our result shows the low velocity exists at depth of 20~30km in mid-lower crust. Compared with previous study, this low velocity zone is larger and deeper both in range and depth. The crustal thickness of 28~35km from our joint inversion is similar to the results from the receiver functions of previous studies. The thinnest crust(28km)is observed at offshore in the north of Quanzhou; while the thickest crust(35km)is located west of Zhangzhou near the Zhenghe-Dapu fault zone. Generally, thinner crustal thickness is found in offshore of Fujian Province, and thicker crustal thickness is in the mainland. However, we also found that crustal thickness becomes thinner along the east side of Yongan-Jinjiang Fault. The values of Pn velocities in the region vary from 7.71 to 8.26km/s. The velocity distribution of the uppermost mantle presents a large inhomogeneity, which is correlated with the distribution of the fault zone. High Pn velocity anomalies are found mainly along the west side of the Zhenghe-Dapu fault zone(F₂), and the east side of the Shaowu-Heyuan fault zone(F₁), which is strip-shaped throughout the central part of Fujian. Low Pn velocity anomalies are observed along the coast and Taiwan Straits, including the Changle-Zhaoan fault zone, the coastal fault zone, and the Fuzhou Basin. We also found a low Pn velocity anomaly zone, which extends to the coast, in the Shaowu-Heyuan fault zone at the junction of the Fujian, Guangdong and Jiangxi Provinces. In the west of Taiwan Straits, both high and low Pn velocity anomalies are observed. Our results show that the historical strong earthquakes(larger than magnitude 6.0) are mainly distributed between positive and negative anomaly zones at different depth profiles of the crust, and similar anomalies distribution also exists at the uppermost mantle, suggesting that the occurrence of strong earthquakes in the region is not only related to the anomalous crustal velocity structure, but also affected by the velocity anomaly structure from the uppermost mantle.