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1.
本研究采用双差定位法对2013年4月20日发生在龙门山断裂带上的四川芦山7.0级强震及主震后48小时内504次余震序列进行重新定位,最终得到328个精定位地震事件.结果表明,余震在水平方向上主要沿龙门山断裂带的山前断裂西南段的大川-双石断裂发生,扩展模式以西南向为主(约23 km)兼有弱东北向(约12 km),并非简单的单侧扩展.在深度方向上,余震主要以铲状结构分布在18～22 km之间.通过拟合精定位后的小震空间分布特征,显示本次地震断层面倾角在15～25 km深度范围内由主震处约44°逐渐向西南向扩展增大至约73°,可能表明断层往西南破裂过程中走滑分量逐渐增强,与2008年汶川地震引起中央断裂倾角由西南向东北变化相类似. 相似文献
2.
Both P- and S-wave arrivals were collected for imaging upper crustal structures in the source region of the April 20, 2013 Lushan earthquake. High-resolution, three-dimensional P and S velocity models were constructed by travel-time tomography. Moreover, more than 3700 aftershocks of the Lushan earthquake were relocated via a grid search method. The P- and S-wave velocity images of the upper crust show largely similar characters, with high and low velocity anomalies, which mark the presence of significant lateral and vertical heterogeneity at the source region of the Lushan earthquake. The characteristics of the velocity anomalies also reflect the associated surface geological tectonics in this region. The distributions of high velocity anomalies of both P- and S-waves to 18 km depth are consistent with the distributions of relocated aftershocks, suggesting that most of the ruptures were localized inside the high velocity region. In contrast, low P and S velocities were found in the surrounding regions without aftershocks, especially in the region to the northeast of the Lushan earthquake. For the relocated aftershocks of the Lushan earthquake from this study, we found that most aftershocks were concentrated in a zone of about 40 km long and 20 km wide, and were located in the hanging wall of Dayi–Mingshan fault. The focal depths of aftershocks increase from the southeast to the northwest region in the direction perpendicular to the fault strike, suggesting that the fault ruptured at an approximate dip angle of 45°. The main depths of the aftershocks in the northwest of the main shock are significantly shallower than expected, revealing the different seismogenic conditions in the source region. 相似文献
3.
High-precision relocation of the aftershock sequence of the January 8, 2022, MS6.9 Menyuan earthquake 
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下载免费PDF全文 The 2022 Menyuan MS6.9 earthquake, which occurred on January 8, is the most destructive earthquake to occur near the Lenglongling (LLL) fault since the 2016 Menyuan MS6.4 earthquake. We relocated the mainshock and aftershocks with phase arrival time observations for three days after the mainshock from the Qinghai Seismic Network using the double-difference method. The total length and width of the aftershock sequence are approximately 32 km and 5 km, respectively, and the aftershocks are mainly concentrated at a depth of 7–12 km. The relocated sequence can be divided into 18 km west and 13 km east segments with a boundary approximately 5 km east of the mainshock, where aftershocks are sparse. The east and west fault structures revealed by aftershock locations differ significantly. The west fault strikes EW and inclines to the south at a 71º–90º angle, whereas the east fault strikes 133º and has a smaller dip angle. Elastic strain accumulates at conjunctions of faults with different slip rates where it is prone to large earthquakes. Based on surface traces of faults, the distribution of relocated earthquake sequence and surface ruptures, the mainshock was determined to have occurred at the conjunction of the Tuolaishan (TLS) fault and LLL fault, and the west and east segments of the aftershock sequence were on the TLS fault and LLL fault, respectively. Aftershocks migrate in the early and late stages of the earthquake sequence. In the first 1.5 h after the mainshock, aftershocks expand westward from the mainshock. In the late stage, seismicity on the northeast side of the east fault is higher than that in other regions. The migration rate of the west segment of the aftershock sequence is approximately 4.5 km/decade and the afterslip may exist in the source region. 相似文献
4.
2012年6月30日新疆维吾尔自治区新源-和静县交界发生MS6.6地震,该地震是2010年青海玉树7.1级地震和2013年4月20日四川芦山7.0级地震之间中国大陆发生的最大的地震.本文基于新疆数字地震台网记录的此次地震序列震相资料,分别用绝对和相对定位方法联合对其进行重新定位,重新定位后余震展布为NW向,主震位置为43.429°N,84.755°E,深度为21.8 km.基于新疆地震台网记录6.6级地震波形数据,本文用CAP方法反演了震源机制解和震源深度.结果显示：MS6.6地震震源机制解：节面Ⅰ走向39°,倾角46°,滑动角12°,节面Ⅱ走向301°,倾角81°,滑动角135°;震源深度为21 km,与利用地震震相到时确定的主震震源深度基本一致.主震震源机制解的节面Ⅱ与伊犁盆地北缘断裂走向和倾角基本一致,综合精确定位余震展布和伊犁盆地北缘断裂性质分析认为,新源-和静MS6.6地震发震构造是伊犁盆地北缘断裂,震源深度为21 km左右,是一个高角的内陆倾滑地震. 相似文献
5.
2014年11月22日在NW向鲜水河断裂带中南段四川康定县发生M6.3级地震,11月25日在该地震震中东南约10km处再次发生M5.8级地震.基于中国国家数字地震台网和四川区域数字地震台网资料,采用多阶段定位方法对本次康定M6.3级地震序列进行了重新定位;利用gCAP(generalized Cut And Paste)矩张量反演方法获得了M6.3和M5.8级地震的震源机制解与矩心深度,分析了本次地震序列的发震构造,并结合历史强震破裂时空分布和2001年以来小震重新定位结果,对鲜水河断裂带中段强震危险性进行了初步探讨.获得的主要结果如下:(1)M6.3级主震震中位于101.69°E、30.27°N,震源初始破裂深度约10km,矩心深度9km;M5.8级地震震中位于101.73°E、30.18°N,初始破裂深度约11km,矩心深度9km.gCAP矩张量反演结果揭示这两次地震双力偶分量占主导,M6.3级地震的最佳双力偶解节面Ⅰ走向143°/倾角82°/滑动角-9°,节面Ⅱ走向234°/倾角81°/滑动角-172°.M5.8级地震最佳双力偶解节面Ⅰ走向151°/倾角83°/滑动角-6°,节面Ⅱ走向242°/倾角84°/滑动角-173°.依据余震分布长轴展布与断裂走向,判定节面Ⅰ为发震断层面,M6.3和M5.8级地震均为带有微小正断分量的左旋走滑型地震.(2)序列中重新定位的459个地震平均震源深度约9km,地震主要集中分布在6~11km深度区间,余震基本发生在M6.3和M5.8级地震震源上部.依据余震密集区展布范围,推测本次康定地震的震源体尺度长约30km、宽约4km、深度范围约6km.M6.3级主震震源附近的余震稀疏区可能是一个较大的凹凸体(asperity),在主震中能量得以充分释放.(3)最初3天的余震主要分布在M6.3级地震NW侧;而M5.8级地震之后的余震主要集中在其震中附近.M6.3级地震以及最初3天的绝大部分余震发生在倾角约82°近直立的NW走向色拉哈断裂上;M5.8级地震与其后的多数余震发生在倾角约83°近直立的NW走向折多塘断裂北端走向向北偏转部位,M5.8级地震可能是M6.3级地震触发相邻的折多塘断裂活动所致.(4)康定M6.3与M5.8级地震发生在鲜水河断裂带乾宁与康定之间的色拉哈强震破裂空段,本次地震破裂尺度较小,尚不足以填补该强震空段.色拉哈段以及相邻的乾宁段7级地震平静时间均已超过其平均复发周期估值,未来几年存在发生7级地震的危险.康定M6.3级地震序列基本填补了震前存在于塔公与康定之间的深部小震空区,未来强震发生在塔公至松林口段深部小震稀疏区内的可能性很大. 相似文献
6.
MECHANISM OF THE 2015 PISHAN,XINJIANG, MS6.5 MAINSHOCK AND RELOCATION OF ITS AFTERSHOCK SEQUENCES 下载免费PDF全文
下载免费PDF全文 Using the digital broadband seismic data recorded by Xinjiang network stations, we obtained focal mechanism of the July 3 Pishan, Xinjiang, MS6.5 earthquake with generalized Cut and Paste(gCAP)inversion method. The strike, dip and rake of first nodal plane are 97°, 27°, 51°, and the second nodal plane are 318°, 70°, 107°. The centroid depth and moment magnitude are calculated to be 12km and 6.4. Combining with the distribution of aftershocks, we conclude that the first nodal plane is the seismogenic fault, and the main shock presents a thrust earthquake at low angle. We relocated 1014 earthquakes using the double-difference algorithm, and finally obtained 937 relocated events. Our results show that the earthquake sequences clearly demonstrate a unilateral extension about 50km nearly in NWW direction, and are mainly located above 25km depth, especially the small earthquakes are predominately located at the shallow parts. Furthermore, the focal depth profile shows a southwestward dipping fault plane at the main shock position, suggesting listric thrust faulting, which is consistent with the dip of the mainshock rupture plane. The spatial distribution of aftershocks represents that the Tarim block was thrust under the West Kunlun orogenic belt. In addition, the dip angle of the fault plane gradually increases along the NWW direction, possibly suggesting a gradual increase of strike-slip component during the NWW rupturing process. From above, we conclude that the Pishan MS6.5 earthquake is the result of Tibet plateau pushing onto the Tarim block from south to north, which further confirms that the continuous collision of India plate and Eurasia plate has strong influence on the seismic activity in and around the Tibet plateau. 相似文献
7.
本研究采用基于贝叶斯理论的绝对定位方法对2014年2月12日新疆于田MS7.3级地震进行绝对定位,得到震中位置为82.56°E、36.04°N、震源深度为12.3 km;采用双差定位法对254个地震序列进行相对定位,得到101个重定位事件.结果显示,主震位于阿尔金断裂带西南端多个分支断裂的交汇处.余震震源主要分布范围在5~10 km深度之间,主震处余震代表的断层面较为陡立,且余震序列呈现出明显的西南向纯单侧扩展模式.沿阿尔金断裂带主震的北东向民丰震区本次地震后显示一个明显的地震丛集,说明本次主震对该震区具有触发作用. 相似文献
8.
基于四川区域地震台网记录的波形资料,利用CAP波形反演方法,同时获取了2013年4月20日芦山M7.0级地震序列中88个M≥3.0级地震的震源机制解、震源矩心深度与矩震级,进而利用应变花（strain rosette）和面应变（areal strain）As值,分析了芦山地震序列震源机制和震源区构造运动与变形特征.获得的主要结果有：（1）芦山M7.0级主震破裂面参数为走向219°/倾角43°/滑动角101°,矩震级为MW6.55,震源矩心深度15 km.芦山地震余震区沿龙门山断裂带走向长约37 km、垂直断裂带走向宽约16 km.主震两侧余震呈不对称分布,主震南西侧余震区长约27 km、北东侧长约10 km.余震分布在7~22 km深度区间,优势分布深度为9~14 km,序列平均深度约13 km,多数余震分布在主震上部.粗略估计的芦山地震震源体体积为37 km×16 km×16 km.（2）面应变As值统计显示,芦山地震序列以逆冲型地震占绝对优势,所占比例超过93%.序列主要受倾向NW、倾角约45°的近NE-SW向逆冲断层控制;部分余震发生在与上述主发震断层近乎垂直的倾向SE的反冲断层上;龙门山断裂带前山断裂可能参与了部分余震活动.P轴近水平且优势方位单一,呈NW-SE向,与龙门山断裂带南段所处区域构造应力场方向一致,反映芦山地震震源区主要受区域构造应力场控制,芦山地震是近NE-SW向断层在近水平的NW-SE向主压应力挤压作用下发生逆冲运动的结果.序列中6次非逆冲型地震均发生在主震震中附近,且主震震中附近P轴仰角变化明显,表明主震对其震中附近局部区域存在明显的应力扰动.（3）序列整体及不同震级段的应变花均呈NW向挤压白瓣形态,显示芦山地震震源区深部构造呈逆冲运动、NW向纯挤压变形.各震级段的应变花方位与形状一致,具有震级自相似性特征,揭示震源区深部构造运动和变形模式与震级无关.（4）不同深度的应变花形态以NW-NWW向挤压白瓣为优势,显示震源区构造无论是总体还是分段均以NW-NWW向挤压变形为特征.但应变花方位与形状随深度仍具有较明显的变化,可能反映了震源区构造变形在深度方向上存在分段差异.（5）芦山地震震源体尺度较小,且主震未发生在龙门山断裂带南段主干断裂上,南段长期积累的应变能未能得到充分释放,南段仍存在发生强震的危险. 相似文献
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利用双差定位方法对西藏比如MS6.1地震序列141次ML≥2.0地震进行重新定位,采用CAP波形反演方法获得主震的震源机制解,并运用最小空间旋转角方法比较不同机构发布的震源机制解的差异。重新定位后主震震中位置为(31.924°N,92.824°E),靠近余震区中心,震源深度为12.8 km;余震分布沿NE向展布,长约18 km。沿NE向深度剖面结果显示,在主震右上方存在5 km×10 km的近椭圆形地震破裂空区。主震的震源机制解为正断兼走滑型,最佳矩心深度为9.3 km,矩震级为5.98。结合重新定位后余震分布、主震与历史地震震源机制解及地质构造背景等分析,认为具有左旋运动性质的安多南缘断裂可能是该次地震序列的主要发震构造。 相似文献
10.
Relocation of the 10 March 2011 Yingjiang,China, earthquake sequence and its tectonic implications 下载免费PDF全文
下载免费PDF全文 Jianshe Lei Guangwei Zhang Furen Xie Yuan Li Youjin Su Lifang Liu Honghu Ma Junwei Zhang 《地震科学（英文版）》2012,25(1):103-110
An earthquake with MS5.8 occurred on 10 March 2011 in Yingjiang county, western Yunnan, China. This earthquake caused 25 deaths and over 250 injuries. In order to better understand the seismotectonics in the region, we collected the arrival time data from the Yunnan seismic observational bulletins during 1 January to 25 March 2011, and precisely hand-picked the arrival times from high-quality seismograms that were recorded by the temporary seismic stations deployed by our Institute of Crustal Dynamics, China Earthquake Administration. Using these arrival times, we relocated all the earthquakes including the Yingjiang mainshock and its aftershocks using the double-difference relocation algorithm. Our results show that the relocated earthquakes dominantly occurred along the ENE direction and formed an upside-down bow-shaped structure in depth. It is also observed that after the Yingjiang mainshock, some aftershocks extended toward the SSE over about 10 km. These results may indicate that the Yingjiang mainshock ruptured a conjugate fault system consisting of the ENE trending Da Yingjiang fault and a SSE trending blind fault. Such structural features could contribute to severely seismic hazards during the moderate-size Yingjiang earthquake. 相似文献