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1.
Noureddine Beghoul Jean-Luc Chatelain Mohamed-Salah Boughacha Hadj Benhallou Rida Dadou Amira Mezioud-Saïch 《Pure and Applied Geophysics》2010,167(3):277-321
Seismic events that occurred during the past half century in the Tellian Atlas, North Africa, are used to establish fundamental seismic empirical relations, tying earthquake magnitude to source parameters (seismic moment, fault plane area, maximal displacement along the fault, and fault plane length). Those empirical relations applied to the overall seismicity from 1716 to present are used to transform the magnitude (or intensity) versus time distribution into (1) cumulative seismic moment versus time, and (2) cumulative displacements versus time. Both of those parameters as well as the computed seismic moment rate, the strain rate along the Tellian Atlas strike, and various other geological observations are consistent with the existence, in the Tellian Atlas, of three distinct active tectonic blocks. These blocks are seismically decoupled from each other, thus allowing consideration of the seismicity as occurring in three different distinct seismotectonic blocks. The cumulative displacement versus time from 1900 to present for each of these tectonic blocks presents a remarkable pattern of recurrence time intervals and precursors associated with major earthquakes. Indeed, most major earthquakes that occurred in these three blocks might have been predicted in time. The Tellian Atlas historical seismicity from the year 881 to the present more substantially confirms these observations, in particular for the western block of the Tellian Atlas. Theoretical determination of recurrence time intervals for the Tellian Atlas large earthquakes using Molnar and Kostrov formalisms is also consistent with these observations. Substantial observations support the fact that the western and central Tellian Atlas are currently at very high seismic risk, in particular the central part. Indeed, most of the accumulated seismic energy in the central Tellian Atlas crust has yet to be released, despite the occurrence of the recent destructive May 2003 Boumerdes earthquake (M w = 6.8). The accumulated seismic energy is equivalent to a magnitude 7.6 earthquake. In situ stress and geodetic measurements, as well as other geophysical field data measurements, are now required to practically check the validity of those observations. 相似文献
2.
Imene Meriem Benbakhti Said Maouche Djelloul Belhai Assia Harbi Jean-François Ritz Ghilles Rabai Ahmed Rezouk Fawzi Doumaz 《Journal of Seismology》2018,22(6):1549-1561
In this work, we reappraise the seismogenic potential of the geologic structures in the western Tell Atlas of Algeria, considered active host to moderate to low magnitude earthquakes. The direct identification of active faults is generally a difficult task in northern Algeria. The active tectonics in the Oran Plio-Quaternary age basin (Northwestern Algeria) is analyzed and characterized through a morpho-structural study combining topographic, geomorphologic, geological, and neotectonic data. Folds and fault scarps affecting Quaternary deposits show that the region is affected by compressional deformation still active nowadays, as shown by the recorded seismic activity. Our new observations enable a better understanding of the present seismotectonic context of the Oran region, particularly with regard to the magnitude and source of the 1790 Oran damaging event. The obtained result helps to shed some light on the elusive active tectonics characterizing this coastal area, and to assess regional seismic hazard, particularly in coastal zones where large seismogenic areas straddle the onshore–offshore zones. 相似文献
3.
Mario Octavio Cotilla Rodriguez 《Journal of Seismology》1998,2(4):323-335
The seismicity of Cuba is briefly presented together with a few fundamental neotectonic elements of the adjacent Caribbean region. The Cuban seismicity catalogue has been extended back to 1528 and it shows that the largest earthquakes occurred in 1766 and 1852 (I = IX MSK). Two types of seismicity (intraplate and interplate) can be distinguished in Cuba. Western and Eastern Seismotectonic Units correspond to intraplate type and the Southeastern Seismotectonic Unit to interplate type. Western Cuba is characterized by a low frequency of earthquake occurrence. Distribution of epicenters is not regular and the most important events mainly concentrate along two regional active fault system (Nortecubana and Surcubana). Due to the lack of seismic stations in this region, the characterization of seismicity is frequently done on the grounds of historical data available from 1693. The main seismogenic source for Cuba is the Bartlett-Cayman fault system, but inland there are other active structures. Some issues about historical and present day Cuban seismological research are also showed. 相似文献
4.
Seismotectonic zonation studies in the Tell Atlas of Algeria, a branch of the Africa-Eurasia plate boundary, provide a valuable input for deterministic seismic hazard calculations. We delineate a number of seismogenic zones from causal relationships established between geological structures and earthquakes and compile a working seismic catalogue mainly from readily available sources. To this catalogue, for a most rational and best-justified hazard analysis, we add estimates of earthquake size translated from active faulting characteristics. We assess the regional seismic hazard using a deterministic procedure based on the computation of complete synthetic seismograms (up to 1 Hz) by the modal summation technique. As a result, we generate seismic hazard maps of maximum velocity, maximum displacement, and design ground acceleration that blend information from geology, historical seismicity and observational seismology, leading to better estimates of the earthquake hazard throughout northern Algeria. Our analysis and the resulting maps illustrate how different the estimate of seismic hazard is based primarily on combined geologic and seismological data with respect to the one for which only information from earthquake catalogues has been used. 相似文献
5.
SEISMO-GEOLOGICAL SIGNATURES FOR IDENTIFYING M≥7.0 EARTHQUAKE RISK AREAS AND THEIR PREMILIMARY APPLICATION IN MAINLAND CHINA 
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下载免费PDF全文 High-magnitude earthquake refers to an earthquake that can produce obvious surface ruptures along its seismogenic fault and its magnitude M is at least equal to 7.0. Prediction and identification of locations, where the high-magnitude earthquakes will occur in potential, is one of the scientific goals of the studies on long-term faulting behavior of active faults and paleo-earthquakes, and is also the key problem of earthquake prediction and forecast. The study of the geological and seismological signatures for identifying M≥7.0 earthquake risk areas and their application is an important part of seismic prediction researches. It can not only promote the development of earthquake science, especially the progress of earthquake monitoring and forecasting, but also be positive for earthquake disaster prevention and effective mitigation of possible earthquake disaster losses. It is also one of the earthquake science problems which the governments, societies and the scientific communities are very concerned about and need to be addressed.
Large or great earthquakes, such as the 2008 Wenchuan earthquake(M8.0), the 2010 Yushu earthquake(M7.1), the 2013 Lushan earthquake(M7.0)and the 2015 Gorkha earthquake(MW7.8), have unceasingly struck the Qinghai-Tibet Plateau and its surrounding areas, which have been attracting attention of a large number of geoscientists both at home and abroad. Owing to good coverage of the seismic networks and GPS sations, a lot of high-quality publications in seismicity, crustal velocity structure, faulting beihavior have been pressed, which gives us a good chance to summarize some common features of these earthquakes. In this paper, seismogenic structural model of these earthquakes, faulting behavior of seismogenic faults, crustal mechanical property, recent straining environment and pre-earthquake seismicity are first analyzed, and then, five kinds of common features for the sismogenic faults where those earthquakes occurred. Those five kinds of commom features are, in fact, the geological and seismological signatures for identifying M≥7.0 earthquake risk areas. The reliability of the obtained sigatures is also discussed in brief. At last, based on the results of 1:50000 active fault mapping, and published seismic tomography and fault-locking studies, an experimental identification of the risk areas for the future large/great earthquakes in the North China and the Qinghai-Tibet Plateau is conducted to test the scientificity and applicability of these obtained sigantures. 相似文献
6.
通过对荣县MS4.9地震震中及附近地区地震监测、地震地质、地震活动背景和区域地震活动性的分析表明,荣县MS4.9地震震前经历了区域地震平静至活跃、再发震的过程,该序列为正常的震群型,震中区及其附近的华蓥山断裂地震带和马边地震带的震后地震学参数均正常。荣县MS4.9地震发震断裂为荣县-威远基底断裂,华蓥山断裂带及其附近地区2018年开始的5—6级地震活跃与川西地区东昆仑断裂带2017年8月九寨沟MS7.0强震的发生存在呼应关系。 相似文献
7.
The plate dynamics in the central western Mediterranean region is characterised by a collision between the Eurasian and African plates. In response to this dynamics, many systems of faults and folds having a NE-SW and E-W trending have been generated along the Tellian Atlas of Algeria. The Oranie region (north western Algeria) has experienced some significant earthquakes in the last centuries, the most important one is that of Oran city on February 9th 1790, Io = XI which destroyed the town completely and caused the loss of many lives. Since 1790 no other event was so disastrous except that of August 18th 1994, Mw = 5.7, which struck Mascara province (Algeria) at 01 h 13 mn GMT. Since the beginning of this century the region has been dominated by a seismic quietness. Thus, no event with magnitude larger than 5.5 have occurred in this area. In relation with this recent event, a seismotectonic framework summarising the tectonic, seismicity and focal solution results is presented. The Maximum Observed Intensities Map (MOI) made for Algeria (Bezzeghoud et al., 1996) is also used to show that the Mascara region is located in an VIII-X intensity zone, which explain partially the casualties caused by the 18/08/1994 (Mw = 5.7) earthquake. This earthquake is not anomalous compared to historical records but is unusual compared to recorded seismicity of this century. The seismotectonic map made in this study and also the review of the focal solutions given by the EMSC, Harvard, and other authors shows that our event is probably associated with a source belonging to a system of faults located in the vicinity of the village of Hacine where the maximum damage was observed. 相似文献
8.
关于识别发震构造的思考与建议 总被引：2，自引：0，他引：2
本文基于地震活动是现代地质构造运动之产物,以及对我国及邻区现代构造条件的认识,指出了构造类比中值得关注的7个问题,提出了发震构造识别方法的新建议,其主要结果如下:(1)发震构造宜定义为,"在现代构造条件下,曾发生或可能发生地震的地质构造"。(2)我国及邻区的现代地质构造同第四纪以来的新构造运动是一脉相承,密不可分的。其中,①现代构造应力场具有明显的区域特征,而且从中更新世以来是基本稳定的;②组成我国大陆不同新构造类型的活动地块(构造单元)之间,存在包括地壳和上地幔横向非均匀性的构造格架差异;③大陆内部各活动地块之间,也存在不同的现代构造形变特征;④宜将中更新世的构造形迹作为与地震活动有关的现代构造形迹看待。(3)在进行构造类比时值得关注的问题有:①宜按活动断裂当前所处的发育阶段来评价其潜在地震;②断裂活动时代并非识别发震构造的充分条件,只有符合现代构造条件的粘~滑断裂,才应识别为大地震的发震构造;③只有同现代构造应力场相适应的先存构造,才可能孕育和发生地震;④对于某些单一断层参数与震级关系的统计结果,未考虑各地震构造区之间现代构造条件和断裂发育阶段的差异,则难以用于构造类比;⑤凡有新生代玄武岩(β6)出露的地段,有可能只发生6.5级以下的地震;⑥地震同地表断裂形迹之间没有必然的联系,尤其仅有断层物质特性分析或测年结果可用时,宜慎重对待为妥;⑦构造类比方法仅适用于识别与先存构造继承性活动有关的发震构造,对于活动地块内部新生或隐伏的发震构造仍无能为力。(4)对于发震构造识别方法的建议是:①以新构造单元为基础划分地震构造区;②按历史重演原则识别曾发生过地震的构造,即凡有较可靠中强以上地震震中、有小地震成丛或呈带分布、或有可信古地震遗迹的地段,均宜识别出符合现代构造条件的发震构造;③根据地震构造区内曾发生过不同震级档地震的构造标志,再按类比原则推断可能的发震构造;④综合评定地震构造区的极限地震,并以此作为区内发震构造最大潜在地震的阀限。 相似文献
9.
1654年礼县8级地震的发震区地处新构造活动强烈的青藏高原东北缘,位于南北地震带中北段,发育多条活动断裂。礼县8级地震发生在黄土覆盖区,距今约370年,受自然侵蚀与人类活动的影响,其地表破裂带和次生灾害现在已经难以分辨。为此,文章收集整理了1970年以来的地震台网和流动台网观测资料,基于地震层析成像方法,经过联合反演计算,研究1654年礼县8级地震的发震构造。研究根据岷县—礼县—两当一线的小震活动分布,推测存在"岷县—礼县—两当断裂",可能是1654年礼县8级地震的发震断裂,但仍需野外地质工作的进一步研究。 相似文献
10.
利用地震剖面研究夏垫断裂西南段的活动性 总被引：5，自引：1，他引：4
地震方法是针对厚覆盖区城市直下型活动断裂的一种不可替代的探测技术,对于不同的探测深度需采用不同的排列长度。为研究夏垫断裂在远离三河-平谷8.0级地震震源区的活动性,我们在该震源区SW方向约30km处开展了中浅层反射地震探测试验,并跨过中浅层地震探测到的夏垫断裂进行了浅层反射地震探测试验。浅层和中浅层地震探测的试验结果表明,在5m道间距的地震剖面上,在200m深度以下夏垫断裂得到了较好的反映,在该深度以上,该断裂反映不明显;在2m道间距的地震剖面上,夏垫断裂错断明显,但剖面上的最浅一组反射波(深度约30m)却没有发生明显错断。由此得出:距1679年三河-平谷8.0级地震震源位置SW方向约30km处,夏垫断裂的活动性减弱 相似文献
11.
LU Ren-qi XU Xi-wei CHEN Li-chun CHEN Gui-hua YAO Qi SUN Jian-bao REN Jun-jie REN Zhi-kun XU Chong WEI Zhan-yu TAN Xi-bin DONG Shao-peng SHI Feng WU Xi-yan 《地震地质》2018,40(1):1-11
On 8 August 8 2017, an MS7.0 earthquake occurred in Jiuzhaigou County, Sichuan Province. Field geological investigations did not find any co-seismic surface rupture in the epicenter area, implying that the seismogenic structure is likely a hidden active fault. Based on the results of the relocated aftershocks, the seismogenic fault was simulated and characterized using the SKUA-GOCAD software. The three-dimensional model of the seismogenic fault was preliminarily constructed, which shows that the main shock of the Jiuzhaigou MS7.0 earthquake occurred at the sharp bending area of the fault surface, similar to the geometry of the active fault that generated several major earthquakes in the Songpan area during 1973-1976. Our study suggests that high seismicity of this area may be closely related to the inhomogeneous geometry of the fault surface. In this work, we collected the historical earthquakes of M ≥ 6.5, and analyzed the geometric and kinematic features of the active faults in the study area. A three-dimensional fault model for the 10 main active faults was constructed, and its limitation in fault modeling was discussed. It could provide evidence for analyzing the seismotectonics of historical earthquakes, exploring the relationships between earthquakes and active faults, and predicting major earthquakes in the future. 相似文献
12.
为了解决我国地震地下流体流动监测网络布设中目前存在的一些问题,以“坚固体孕震模式”为理论基础,以西秦岭北缘断裂带为研究对象,通过高密度地下流体背景值探测,结合地壳垂直形变特征以及地震活动性特征,寻找区域活动断裂带流体与形变以及地震活动的耦合段及断层气响应的灵敏点,综合判断断裂带活动分段性。断层形变、地震活动与地下流体活动有着良好的对应性与耦合关系,震源区均表现为“断层闭锁区”特性,发震地点都显示出一种相对平静的状态。基于以上研究,形成从活动断裂带—“坚固体”闭锁段—近震区前兆场地的追踪思路,规划具有一定物理预报思想的标准化断层气流动观测方案,并建立研究区域观测网络的雏形。这对今后全国地震重点危险区流体流动监测台网布设提供技术思路,并为我国地震预报、震情跟踪及防震减灾工作提供重要依据。 相似文献
13.
In this paper we discuss the seismogenic structures of the two earthquakes occurring in the Beibu Gulf waters,based on the investigation of geological structure,faults,geophysical fields,seismicity and earthquake focal mechanism.The results show that the NEE trending faults along the boundary of the Wushi depression are the dominating seismogenic structures,and the NW trending faults are the key factors of stress concentration.The results also show that high seismicity has a significant relationship with the late Cenozoic deposition center in the Beibu Gulf,and their NE-NEE trending boundary faults are important to the identification of seismogenic structures.The special arcuate fault segment or the intersection point of the NW trending faults and NE-NEE trending boundary faults is a possible location of future earthquakes. 相似文献
14.
The main objective of the research work isthe homogenisation of the two recentAlgerian earthquake catalogues for thecommon covered period of time, from 1900 to1990, for the region under considerationlimited by [33°N–38°N,4°E-9.5°E] and the updatingof the catalogue for the twentieth century(1900–2000). To mitigate the deficiencyof the incompleteness of catalogue, aneffort was made to establish a correlationbetween surface-wave magnitude Ms andbody-wave magnitude mb in the form ofMs = a + b (mb). A complete, exact andhomogeneous earthquake catalogue as much aspossible, comprising 870 seismic events,has been compiled. Seismicity analysis ofthe region shows a strong concentration ofseismicity along a band of no more than400 km width oriented mainly in theeast-west direction parallel to the coast.Moreover, earthquakes in this zone arerather associated to strike-slip mechanism.The focal mechanism show a regional stressregime that corresponds to horizontalcompression in NW-SE to N-S direction. As aresult of the review of the seismicity ofnorth-eastern Algeria from the compilationof checked and corrected data and itscorrelation with other geologic andgeophysical investigations based ondocumentary sources, it was possible toconstruct a most complete seismotectonicmap. It leads also to delineate fourseismogenic zones in the Tellian Atlas, aless important zone in the Saharan Atlas, asixth zone at the boundary of both Atlasand finally, a seventh one along thecoastal zone. The seismicity-active faultscorrelation of some of these defined zonesis examined in details with a specialattention to the Saharan Atlas zone, theHodna and Biban zone as well as Soummam andBabor zone where further research workallowed to find some neotectonic featuresconsidered as a significant sign of recenttectonic activity. 相似文献
15.
徐州活动断层探测项目主要断层活动性研究 总被引：2，自引：0，他引：2
对徐州市主要可能的发震断层开展了活动性探测及地震危险性评价工作,这对徐州市开展防震减灾工作具有重大意义.根据前人资料,分析了威胁徐州市区安全的主要5条隐伏断层,它们分别为幕集-刘集断裂、不老河断裂、废黄河断裂、班井断裂和邵楼断裂.同时根据徐州市活动断层探测项目的要求,针对这5条主要断层开展了浅层地震勘探、钻孔联合剖面探测、野外地震地质调查等相关工作,评价了这5条断层的活动历史、活动性质、规模、展布和地貌特征,及其最新活动时代.结果表明,废黄河断裂最新活动时代为中更新世中期,邵楼断裂最新活动时代为早更新世,这2条断层是目标区具备一定程度发震能力和地震危险性最大的断层. 相似文献
16.
芦山地震发生在龙门山断裂带前缘.关于芦山地震的发震断层,有的认为是前山断裂——双石—大川断裂,有的认为是山前断裂——大邑断裂拟或其他隐伏断裂,发震断裂究竟是哪条断裂以及芦山地震是不是汶川地震的余震?目前仍存在较大争议.震后穿过芦山地震区完成了一条长近40km的深地震反射剖面,以确定芦山地震的发震构造.反射剖面显示浅部褶皱和断裂构造发育,在上地壳存在6条逆冲断裂,下地壳存在一条非常明显的变形转换带,在深度16km左右还存在一个滑脱层,浅部的6条断裂最终都归并到该滑脱层上.参考主余震精定位结果,芦山地震的发震断裂应该是位于双石—大川断裂和大邑断裂之间的隐伏断裂F4,F2和F3断裂受控于发震断裂而活动,形成剖面上"Y"字型余震分布现象.隐伏断裂F4属山前断裂,不是前山断裂,因此芦山地震不是汶川地震的余震. 相似文献
17.
Pakistan and the western Himalaya is a region of high seismic activity located at the triple junction between the Arabian, Eurasian and Indian plates. Four devastating earthquakes have resulted in significant numbers of fatalities in Pakistan and the surrounding region in the past century (Quetta, 1935; Makran, 1945; Pattan, 1974 and the recent 2005 Kashmir earthquake). It is therefore necessary to develop an understanding of the spatial distribution of seismicity and the potential seismogenic sources across the region. This forms an important basis for the calculation of seismic hazard; a crucial input in seismic design codes needed to begin to effectively mitigate the high earthquake risk in Pakistan. The development of seismogenic source zones for seismic hazard analysis is driven by both geological and seismotectonic inputs. Despite the many developments in seismic hazard in recent decades, the manner in which seismotectonic information feeds the definition of the seismic source can, in many parts of the world including Pakistan and the surrounding regions, remain a subjective process driven primarily by expert judgment. Whilst much research is ongoing to map and characterise active faults in Pakistan, knowledge of the seismogenic properties of the active faults is still incomplete in much of the region. Consequently, seismicity, both historical and instrumental, remains a primary guide to the seismogenic sources of Pakistan. This study utilises a cluster analysis approach for the purposes of identifying spatial differences in seismicity, which can be utilised to form a basis for delineating seismogenic source regions. An effort is made to examine seismicity partitioning for Pakistan with respect to earthquake database, seismic cluster analysis and seismic partitions in a seismic hazard context. A magnitude homogenous earthquake catalogue has been compiled using various available earthquake data. The earthquake catalogue covers a time span from 1930 to 2007 and an area from 23.00° to 39.00°N and 59.00° to 80.00°E. A threshold magnitude of 5.2 is considered for K-means cluster analysis. The current study uses the traditional metrics of cluster quality, in addition to a seismic hazard contextual metric to attempt to constrain the preferred number of clusters found in the data. The spatial distribution of earthquakes from the catalogue was used to define the seismic clusters for Pakistan, which can be used further in the process of defining seismogenic sources and corresponding earthquake recurrence models for estimates of seismic hazard and risk in Pakistan. Consideration of the different approaches to cluster validation in a seismic hazard context suggests that Pakistan may be divided into K?=?19 seismic clusters, including some portions of the neighbouring countries of Afghanistan, Tajikistan and India. 相似文献
18.
SEISMOTECTONIC BACKGROUND AND RECURRENCE INTERVAL OF GREAT EARTHQUAKES IN 1679 SANHE- PINGGU M = 8 EARTHQUAKE AREA 总被引：2，自引：3，他引：2 下载免费PDF全文
下载免费PDF全文 Xiang Hong-fa Fang Zhong-jing Xu Jie Li Ru-cheng Jia San-fa Hao Shu-jian Wang Jing-bo and Zhang Wan-xia 《地震地质》1988,10(1):29
Basined on comprehensive prospecting and investigation, the authors have ascertained that the 1679 San-he-Pinggu M = 8 earthquake occurred in the intersection region of active faults having deep-seated structural background. The NE-trending New Xiadian Fault, which was characterized by dextrall tensile-shear dislocation, was the seismogenic fault of the 1679 M = 8 earthquake. It is suggested that the macroscopic epicenter of the earthquake should be located in Pangezhuang area, where the vertical displacement of seismic faul' was up to 3.16m. According to the average seismic slip rate in this area, and the displacement value of earthequake with a certain magnitude, the recurrence interval of M = 7.5, M=7.0 and M = 8.5 earthquakes in the magistoseismic area of 1679 M = 8 earthquake on Xiadian Fault Zone have been estimated to be 3800,1750, and 800 years (the lower limit), respectively 相似文献
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THE SOURCE PARAMETERS AND SEISMOTECTONIC IMPLICATIONS OF THE SEPTEMBER 4, 2017 ML4.4 LINCHENG EARTHQUAKE 下载免费PDF全文
下载免费PDF全文 LI He XIE Zu-jun WANG Yi-xi WANG Xiao-shan DONG Yi-bing ZHANG Hui PENG Zhao LIU Wen-bing GAO Ye WANG Li-xia 《地震地质》2019,41(3):670-689
At 3:05, September 4, 2017, an ML4.4 earthquake occurred in Lincheng County, Xingtai City, Hebei Province, which was felt obviously by surrounding areas. Approximately 60km away from the hypocenter of Xingtai MS7.2 earthquake in 1966, this event is the most noticeable earthquake in this area in recent years. On the one hand, people are still shocked by the 1966 Xingtai earthquake that caused huge disaster, on the other hand, Lincheng County is lack of strong earthquakes. Therefore, this quake has aroused widespread concerns by the government, society and seismologists. It is necessary to clarify whether the seismogenic structure of this event is consistent with the previous seismicity and whether it has any new implications for the seismic activity and seismic hazard in this region. Therefore, it is of great significance to study its seismogenic mechanism for understanding the earthquake activity in Xingtai region where a MS7.2 earthquake had occurred in 1966.
In this study, the Lincheng earthquake and its aftershocks are relocated using the multi-step locating method, and the focal mechanism and focal depth are determined by the "generalized Cut and Paste"(gCAP)method. The reliability of the results is analyzed based on the data of Hebei regional seismic network. In order to better constrain the focal depth, the depth phase sPL fitting method is applied to the relocation of focal depth. The inversion and constraint results show that aftershocks are mainly distributed along NE direction and dip to SE direction as revealed by depth profiles. Focal depths of aftershocks are concentrated in the depths of 6.5~8.2km with an average of about 7km. The best double-couple solution of the mainshock is 276°, 69° and -40° for strike, dip and slip angle for nodal plane I and 23°, 53° and -153° for nodal plane Ⅱ, respectively, revealing that it is a strike-slip event with a small amount of normal-fault component. The initial rupture depth of mainshock is about 7.5km obtained by the relocation while the centroid depth is 6km derived from gCAP method which was also verified by the seismic depth phase sPL observed by several stations, indicating the earthquake is ruptured from deep to shallow. Combined with the research results on regional geological structure and the seismic sequence relocation results, it is concluded that the nodal plane Ⅱ is the seismogenic fault plane of this earthquake.
There are several active faults around the hypocenter of Lincheng earthquake sequence, however, none of the known faults on the current understanding is completely consistent with the seismogenic fault. To determine the seismogenic mechanism, the lucubrated research of the MS7.2 Xingtai earthquake in 1966 could provide a powerful reference. The seismic tectonic characteristics of the 1966 Xingtai earthquake sequence could be summarized as follows:There are tensional fault in the shallow crust and steep dip hidden fault in the middle and lower crust, however, the two faults are not connected but separated by the shear slip surfaces which are widely distributed in the middle crust; the seismic source is located between the hidden fault in the lower crust and the extensional fault in the upper crust; the earthquake began to rupture in the deep dip fault in the mid-lower crust and then ruptured upward to the extensional fault in the shallow crust, and the two fault systems were broken successively. From the earthquake rupture revealed by the seismic sequence location, the Lincheng earthquake also has the semblable feature of rupturing from deep to shallow. However, due to the much smaller magnitude of this event than that of the 1966 earthquake, the accumulated stress was not high enough to tear the fracture of the detachment surface whose existence in Lincheng region was confirmed clearly by the results of Lincheng-Julu deep reflection seismology and reach to the shallower fault. Therefore, by the revelation of the seismogenic mechanism of the 1966 Xingtai earthquake, the seismogenic fault of Lincheng earthquake is presumed to be a concealed fault possessing a potential of both strike-slip and small normal faulting component and located below the detachment surface in Lincheng area. The tectonic significance indicated by this earthquake is that the event was a stress adjustment of the deep fault and did not lead to the rupture of the shallow fault. Therefore, this area still has potential seismic hazard to a certain extent. 相似文献