共查询到19条相似文献，搜索用时 140 毫秒
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利用区域构造、小湾库区水载荷变化及云南省区域地震台网2000—2021年的地震监测资料,对小湾水库影响区内水库蓄水前后地震活动空间、频度、强度等进行综合分析,并对区域断层性质、库水位载荷变化、震源机制解、地震应力降参数进行深入分析。结果显示:小湾水库影响区及附近第四纪断裂构造交汇,环境复杂且存在应力水平较高区域;水库蓄水对库区基底岩层及库岸岩体影响显著,地震活动明显增强;水库影响区地震空间分布明显受区域构造控制;在水载荷变化的影响下,触发了构造区的应力释放,发生了走滑断层性质破裂的2015年昌宁5.1级地震。 相似文献
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云南省糯扎渡水库蓄水前后地震活动性研究 总被引：1，自引：0，他引：1
采用2008年6月至2013年10月糯扎渡水库地震台网记录的6 300个地震,对水库蓄水前后的地震活动进行分析,发现库区蓄水后,地震频度与水位同步增长,地震活动显著增强,表明库区有水库诱发地震发生。蓄水前后的地震活动图像显示,澜沧江上景谷、双江交界处的小震活动增加最为显著,采用Hypodd双差相对定位方法对该震群进行了重新定位,定位后地震在空间上更为丛集,地震震源深度从0~20 km都有分布。该震群发生在窝拖寨断裂上,该断裂历史上曾发生过5.3级地震,因此分析认为,该震群的发生时间虽与水位相关,但可能是触发了构造地震,所以震源深度显现的是构造活动的特征。 相似文献
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云南小湾水库蓄水后P波速度结构的双差地震层析成像研究 总被引：2，自引：1，他引：1
联合小湾水库库区及其附近11249个地震的P波绝对到时、相对到时数据,利用双差地震层析成像方法反演得到小湾水库蓄水后2008年12月16日～2011年6月30日和2011年7月1日～2016年12月31日2个时间段内库区及其附近的地震重定位结果和三维P波速度结构。结果表明,蓄水后黑惠江段和小湾水库回水澜沧江段地震的增多与水库蓄水有关。由于水体渗透导致孔隙压变化,并随着时间的推移孔隙压变化朝着更深的部位扩散,地震震源深度也随之向深部扩散,进而导致介质变化和P波速度降低。蓄水回水至澜沧江保山段后该区域地震增多,P波速度下降,库水渗透作用为主控因素,该区域地下一定深度的地质构造有利于库水的快速渗透。初步判定2015年10月30日云南昌宁M_S5.1地震余震序列是与蓄水有关的柯街断裂上的构造地震。同时,也存在着与蓄水相关性不大的属于构造地震的活动,如云南施甸一带历来地震多发,施甸2010年6月1日M_L4.8、2012年9月11日M_S4.7地震序列均属于构造地震,与水库蓄水无关。 相似文献
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湖南省黄石水库诱发地震的形成条件及成因探讨 总被引：2，自引：0，他引：2
在湖南桃源县黄石水库库区，由于张扭性活断层和深部岩溶的存在，水库蓄水后产生的附加应力场及水库区增强的岩石孔隙流体压力诱发了断层的断滑，使得库区应力集中区和岩溶发育区合二为一的地带发生构造型地震，从而在震活动的时间序列、空间规律，地震与库水位关系，震源深度、震情等方面表现出构造水库诱发地震的特点。 相似文献
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根据2008年9月至2013年10月金沙江下游水库地震台网监测资料,分析了蓄水期间水库地震影响区的地震活动和震源机制。向家坝水库蓄水1年多,蓄水后库首区A、B段的地震活动频次和强度都维持在较低水平。蓄水期间地震活动显著增加,集中分布在库区C段,并不是蓄水初期地震活动就增加,与库区2013年6月启动第二阶段蓄水有一定相关性,强度在3级地震活动水平。增加的地震活动位于近南北走向的翼子坝、玛瑙断裂的中段。这些局部地段蓄水后发生的地震,其震源的力学机制多为倾滑或正断型,分析认为部分地震为水库诱发岩溶或塌陷型地震,多数仍属构造地震。本文结果为水库诱发地震的研究提供了资料和震例。 相似文献
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结合微震活动的流体作用强度检测及孔隙压扩散模拟,讨论了三峡库区不同时期微震活动的主要影响因素。以2008年9月蓄水季为界划分前、后期,前期流体渗透导致的孔隙压力增加,使裂隙或断层面强度降低,是库区微震活动的主要影响因素,这一时期微震频次及ETAS模型参数μ值有起伏地缓慢增大,与库水位加卸载过程关系不明显; 后期由于流体渗透引起的孔隙压力变化趋于零,在新的流体平衡条件下,库水位加卸载过程所导致的裂隙或断层面上的应力变化,成为库区微震活动的主要影响因素,这一时期微震频次及μ值显示出与水位变化明显的关联特征。库区小震震源深度的时间变化支持上述观点。在此基础上,进一步讨论了水库“诱发”和水库“触发”地震的力学差异,认为前者主要缘于流体渗透导致的裂隙或断层面强度的“主动”降低,后者则主要与库水加卸载所导致的裂隙或断层面上应力增强有关。进一步推论认为,流体对小地震“诱发”、“触发”皆可能发生,但中强地震缘于流体“诱发”的可能性非常小,对水库区发生的中强地震,流体仅可能对处于临界状态的断层系统起到“触发”作用。 相似文献
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为了解水库蓄水过程中,水库诱发地震活动的动态响应机制,本文建立了针对水库诱发地震(Reservoir-induced seismicity,RIS)定量化研究的数理模型,并以紫坪铺水库为例,对库区地质构造及水文地质结构条件、水库蓄水后库区小震活动时空演化特征进行了详细的研究.在此基础上,利用有限元方法计算了水库蓄水过程中弹性附加应力场、有效附加应力场、孔隙压力和断层稳定性的动态变化,讨论了RIS时空演化与库水加卸载及渗透过程的动态响应关系.结果表明:(1) RIS诱发机制的定量化模型可分为2个层次:一是以孔隙介质为载体的流体渗流对岩体变形和稳定性的影响,由流-固耦合形式的岩体变形与孔隙渗流模型进行描述;二是对断层相关的RIS定量研究可将水库附加水头压力沿断层面(区)的扩散与断层库仑应力变化联系起来.两种形式模型方法的结合能为RIS定量研究提供一个相对宏观的力学框架;(2) 断裂渗透结构对孔隙压力变化下断裂的力学响应具有重要的影响,研究区主干断裂可能属于一种上盘破碎带导水、下盘地层及断层核阻水的"下阻上导型"的渗透结构类型,不同程度的具有使地表水体向深部渗流的通道性.库区深部岩体渗透稳定性的差异在很大程度上导致了诱发地震活动对岩性条件的依赖.(3) 紫坪铺水库蓄水后,小震活动在空间分布上呈现出条带状分布、丛集分布和地震迁移的特点,小震震源深度优势分布在地下4~10 km范围内,在通济场断裂与安县-灌县断裂的深部汇聚区域震源分布最为密集.同时,小震活动主要集中发生在脆性程度高、渗透稳定性低的碳酸盐岩地层中,而在岩性较软弱、渗透稳定性高的三叠系须家河组砂泥岩和煤系地层中很少有地震发生.在水库蓄水后地震活动的时间响应特征上,水库西南侧和东北侧两个丛集区的小震活动可能属于"快速响应型"RIS,而都江堰小震群活动可能属于"滞后响应型"诱发地震活动;(4) RIS的发生与库水加卸载及渗透过程中库底岩体有效应力的变化密切相关.在以挤压为主的构造应力环境中,库体荷载作用的结果一般会使库底断层更趋向稳定,而水库附加水头压力扩散的效应则是促使断层趋向失稳,正是这个矛盾双方相互制约与平衡的动态过程,控制了断层库仑应力变化的取向,从而决定了RIS时空演化的规律. 相似文献
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龙滩库区蓄水后地震性质分析 总被引：2，自引：0，他引：2
龙滩水库2006年10月蓄水以来,库区地震活动频繁,这可能是原有构造地震的进一步活动,也可能是水库诱发地震。因此,有必要对龙滩水库蓄水后发生的地震性质进行判断。本文根据国内外已发生水库诱发地震震例资料和以往经验,结合龙滩库区具体情况,利用定性判断法和概率统计法对龙滩库区地震性质进行验证和判断,结果认为:龙滩库区蓄水后发生的地震属诱发地震。 相似文献
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福建水口库区地震性质讨论 总被引：1，自引：0，他引：1
许振栋 《地震地磁观测与研究》2004,25(2):28-32
水口水库建成蓄水后,库区出现了频繁的地震活动,这可能是原有构造地震的进一步活动,也可能是水库诱发的。因此,有必要对水口水库蓄水后发生的地震性质进行判断。本文根据国内外已发生水库诱发地震震例资料和以往经验,结合水口库区具体情况,用定性判断法、概率法、扩散系数判别法等,对水口库区地震性质进行验证和判断,结果认为：水口库区蓄水后发生的地震属诱发地震。 相似文献
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CHARACTERISTICS OF TECTONIC STRESS FIELD OF THE XIAOWAN RESERVOIR BEFORE AND AFTER THE IMPOUNDMENT 
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下载免费PDF全文 Using the seismic waveform data of Xiaowan seismic network and Yunnan seismic network, we determined the focal mechanisms of 36 earthquakes(ML ≥ 3.0)from Jun. 2005 to Dec. 2008 and 51 earthquakes(ML ≥ 2.5)from Jan. 2009 to Dec. 2015 by generalized polarity and amplitude technique.
We inverted tectonic stress field of the Xiaowan reservoir before impounding, using the focal mechanisms of 36 earthquakes(ML ≥ 3.0)from Jun. 2005 to Dec. 2008 and CAP solutions of 58 earthquakes(ML ≥ 4.0)collected and the solutions in the Global Centroid Moment Tensor(GCMT)catalog; We inverted local stress field of the reservoir-triggered earthquake clustering area, using 51 earthquakes(ML ≥ 2.5)from Jan. 2009 to Dec. 2015.
Focal mechanisms statistics show that, the Weixi-Qiaohou Fault is the seismic fault. Focal mechanisms were strike-slip type in initial stage, but normal fault type in later stage. Focal depths statistics of 51 earthquakes(ML ≥ 2.5)show that, the average value of focal depths in period Ⅰ, period Ⅱ and period Ⅲ are 8.2km, 7.3km and 7.8km respectively and the standard deviations are 4.3km, 3.5km and 6.0km respectively. The average value of focal depths is basically stable in different period, only the standard deviation is slightly different. Therefore, there is not positive connection between focal depth and deviation of focal mechanisms. What's more, there are 2 earthquakes(number 46 and number 47 in Fig.5 and Table 3)with almost the same magnitude, epicenter and focal depth, but they have different faulting types as normal and strike-slip. The focal mechanism of event No.46 is strike:302°, dip:40° and rake:-97° for plane Ⅰ, however, the focal mechanism of event No.47 is strike:292°, dip:82° and rake:140° for plane Ⅰ. Likewise, earthquake of number 3 and number 18 have similar characteristic. Therefore, the obvious focal mechanism difference of similar earthquake pair indicates the complexity of Weixi-Qiaohou Fault.
Considering the quiet-active character of reservoir-triggered earthquakes, we discussed the change of local stress field in different period. The σ1 of tectonic stress field was in the near-south direction, with a dip angle of 14° before the impoundment, however, the direction of σ1 of local stress field changed continuously, with the dip angle getting larger after the impoundment. The direction of σ1 of local stress field of reservoir-triggered earthquake clustering area is close to the strike of Weixi-Qiaohou Fault, and reservoir impoundment increased the shear stress in the fault, so the weakening of fault was beneficial to trigger earthquakes. Comprehensive analysis suggests that fluid permeation and pore pressure diffusion caused by the water impounding, and the weakening of fault caused by local stress field are the key factors to trigger earthquake in the Xiaowan reservoir. 相似文献
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Accurate relocation of earthquakes in central-western China using the double-difference earthquake location algorithm 总被引：3，自引：0，他引：3
The double-difference earthquake relocation algorithm (DD algorithm) has been applied to the accurate relocation of 10057 earthquakes in the central-western China (21°-36°N, 98°-112E°) during the period of 1992-1999. In total, 79706 readings for P waves and 72169 readings for S waves were used in the relocation, and the source parameters of 6496 events were obtained. The relocation results revealed a more complete picture of the hypocentral distribution in the central-western China. In several seismic belts the relocated epicenters present a more defined lineation feature, reflecting the close correlation between the seismicity and the active tectonic structures. The relocated focal depths confirmed that most earthquakes (91 percent of the 6496 relocated events) in the central-western China were located at shallower depths not deeper than 20 km. The distribution of focal depths indicates that the seismogenic layer in the central-western China is located in the upper-mid crust with its thickness no deeper than 20 km. 相似文献
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Thai Anh Tuan N. Purnachandra Rao Kalpna Gahalaut Cao Dinh Trong Le Van Dung Cao Chien K. Mallika 《Journal of Seismology》2017,21(5):1131-1143
In the Song Tranh 2 (ST2) hydropower reservoir located in the Quang Nam province, Central Vietnam, earthquakes started occurring soon after impoundment of the reservoir in late 2010. Earthquakes continue to occur in the region, and two earthquakes of M 4.6 and 4.7 on October 22, 2012 and November 15, 2012, respectively, have been reported (Trieu et al. 2014; Giang et al. 2015) in the vicinity of the reservoir. In the present study, b-value has been estimated, and focal mechanism solutions have been computed for the first time using moment tensor inversion approach. Also, the influence of impoundment of reservoir on the occurrence of earthquakes has been computed for the ST2 region based on Coulomb stress. A quality data set of 595 earthquakes recorded for the period of October 2012 to April 2014 at ten stations of the seismic network operated by the Institute of Geophysics (IGP) has been used to calculate b-values for the northern and southern seismicity clusters of the region. In general, the b-values associated with reservoir-triggered seismicity (RTS) are found to be higher than the regional b-values in the frequency-magnitude relation of earthquakes. For the ST2 region, it is found that the b-values for the northern and southern clusters are 0.94 ± 0.04 and 0.90 ± 0.04, respectively. Focal mechanism solutions obtained for the two earthquakes close to the reservoir have a right-lateral strike-slip mechanism, with the preferred planes trending NW-SE. These results are concurrent with the orientation of the nearby local surface faults, which we confirm as the active faults in this region. Influence of the stresses due to reservoir water load on the local seismicity is computed based on the obtained focal mechanism by using the concept of fault stability. It is found that most of the earthquakes occur in the positive Coulomb stress region, which shows the influence of reservoir impoundment on earthquake occurrence in the vicinity. Our results suggest that the local earthquakes are triggered by the impoundment of the ST2 reservoir. 相似文献
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Awad Hassoup 《Journal of Seismology》2002,6(4):459-467
The data described here are obtained from the continuous record of earthquakeactivity and lake water-level variation in the Lake Aswan area in Egypt between 1982 and 1997. The seismicity is monitored by a local telemetered seismograph network. The hypocentral parameters of earthquakes have been determined using Hypo71. The earthquake foci are distributed in two seismic zones, shallow and deep in the crust. Shallow events have focal depths of less than 10 km. Deep events extend from 10 to 30 km. The temporal sequence of seismicity iscorrelated with both the water-level variation and the average daily change of the water level in the lake Aswan. The temporal variation of the seismicityindicates that there are only six sequences of increased seismic activity during 1982–1997. The correlation between the seismic activity and the daily variation of the lake water level is poorly observed except with the June 1987 events swarm, which was accompanied by the presence of an anomaly in rate of water level decreasing. It is concluded that the increase in seismic activity in the Aswan reservoir is demonstrating an example of rapid reservoir-triggered seismicity. The deeper seismic sequence in this area, which was associated with the November 14, 1981 mainshock (MD = 5.7), and the earlier seismicity (1981–82), has been correlated with a deeper high velocity anomaly (Awad and Mizoue, 1995-b). 相似文献
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The double-difference earthquake relocation algorithm (DD algorithm) has been applied to the accurate relocation of 10057 earthquakes in the central-western China (21°-36°N, 98°-112E°) during the period of 1992-1999. In total, 79706 readings for P waves and 72169 readings for S waves were used in the relocation, and the source parameters of 6496 events were obtained. The relocation results revealed a more complete picture of the hypocentral distribution in the central-western China. In several seismic belts the relocated epicenters present a more defined lineation feature, reflecting the close correlation between the seismicity and the active tectonic structures. The relocated focal depths confirmed that most earthquakes (91 percent of the 6496 relocated events) in the central-western China were located at shallower depths not deeper than 20 km. The distribution of focal depths indicates that the seismogenic layer in the central-western China is located in the upper-mid crust with its thickness no deeper than 20 km. 相似文献
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Machine learning-based automatic construction of earthquake catalog for reservoir areas in multiple river basins of Guizhou province,China 下载免费PDF全文
下载免费PDF全文 Large reservoirs have the risk of reservoir induced seismicity. Accurately detecting and locating microseismic events are crucial when studying reservoir earthquakes. Automatic earthquake monitoring in reservoir areas is one of the effective measures for earthquake disaster prevention and mitigation. In this study, we first applied the automatic location workflow (named LOC-FLOW) to process 14-day continuous waveform data from several reservoir areas in different river basins of Guizhou province. Compared with the manual seismic catalog, the recall rate of seismic event detection using the workflow was 83.9%. Of the detected earthquakes, 88.9% had an onset time difference below 1 s, 81.8% has a deviation in epicenter location within 5 km, and 77.8% had a focal depth difference of less than 5 km, indicating that the workflow has good generalization capacity in reservoir areas. We further applied the workflow to retrospectively process continuous waveform data recorded from 2020 to the first half of 2021 in reservoir areas in multiple river basins of western Guizhou province and identified five times the number of seismic events obtained through manual processing. Compared with manual processing of seismic catalog, the completeness magnitude had decreased from 1.3 to 0.8, and a b-value of 1.25 was calculated for seismicity in western Guizhou province, consistent with the b-values obtained for the reservoir area in previous studies. Our results show that seismicity levels were relatively low around large reservoirs that were impounded over 15 years ago, and there is no significant correlation between the seismicity in these areas and reservoir impoundment. Seismicity patterns were notably different around two large reservoirs that were only impounded about 12 years ago, which may be explained by differences in reservoir storage capacity, the geologic and tectonic settings, hydrogeological characteristics, and active fault the reservoir areas. Prominent seismicity persisted around two large reservoirs that have been impounded for less than 10 years. These events were clustered and had relatively shallow focal depths. The impoundment of the Jiayan Reservoir had not officially begun during this study period, but earthquake location results suggested a high seismicity level in this reservoir area. Therefore, any seismicity in this reservoir area after the official impoundment deserves special attention. 相似文献
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统计整理小浪底库区近场地震，对地震位置进行精确定位，并计算较大地震的震源机制解，结合水库地震的活动特点，对地震活动和震源机制特征进行分析，认为小浪底库区地震活动具有水库地震特征，且同时受区域地质构造影响。 相似文献