2011年云南盈江Ms5.8地震及其余震序列重定位

使用川滇地区三维走时表和三维速度模型,利用单纯形法对2011年3月10日云南盈江Ms5.8地震进行了重新定位.震中位置为97.901°E,24.677°N;震源深度13.1 km.使用双差定位方法对其余震序列进行了重定位.余震呈现明显的时空分布特征:余震主要分布在大盈江断裂的两侧及中段和北东段的转折处,余震带长度约12...     

2011 年云南盈江MS 5. 8 地震序列重定位

利用云南数字地震台网和腾冲火山台网记录的2011 年1 ～ 12 月震相数据,采用Hypo2000、HypoDD 定位方法对2011 年盈江MS5. 8 地震序列的前震、余震进行了重新定位。定位结果显示地震分布较定位前更为集中。前震活动主要沿大盈江断裂呈NE 走向分布。余震呈共轭分布:一支沿大盈江断裂呈NE 向分布,另一支沿垂直于大盈江断裂的隐伏错断呈SSE向分布。余震分布存在着稀疏段落,可能对应着前震主要破裂区域。     

利用双差法对2005年江西九江-瑞昌5.7级地震序列重新定位

利用江西地震台网数据,对2005年江西九江-瑞昌5.7级地震序列86个ML≥1.0余震序列用双差法重新定位,定位后得到其中60次地震的基本参数.重新定位后的结果与江西地震台网定位的原始结果进行比较,发现:①重新定位结果显示了震中分布比较集中,震中位置向广济断裂带靠近,定位后的震中空间分布与地面约34°角;②震源深度优势分布集中在7～10 km以内,平均深度为9 km;③重新定位后定位残差由原来的1.21 s降为0.16 s,震源位置的估算误差在EW方向平均为0.21 km,在NS方向平均为0.32 km,在垂直方向平均为0.34 km.     

Relocation of the M8.0 Wenchuan earthquake and its aftershock sequence

We relocated M8.0 Wenchuan earthquake and 2706 aftershocks with M≥2.0 using double-difference algorithm and obtained relocations of 2553 events. To reduce the influence of lateral variation in crustal and upper mantle velocity structure, we used different velocity models for the east and west side of Longmenshan fault zone. In the relocation process, we added seismic data from portable seismic sta-tions close to the shocks to constrain focal depths. The precisions in E-W, N-S, and U-D directions after relocation are 0.6, 0.7, and 2.5 km respectively. The relocation results show that the aftershock epi-centers of Wenchuan earthquake were distributed in NE-SW direction, with a total length of about 330 km. The aftershocks were concentrated on the west side of the central fault of Longmenshan fault zone, excluding those on the north of Qingchuan, which obviously deviated from the surface fault and passed through Pingwu-Qingchuan fault in the north. The dominant focal depths of the aftershocks are between 5 and 20 km, the average depth is 13.3 km, and the depth of the relocated main shock is 16.0 km. The depth profile reveals that focal depth distribution in some of the areas is characterized by high-angle westward dipping. The rupture mode of the main shock features reverse faulting in the south, with a large strike-slip component in the north.     

Relocation of the M 8.0 Wenchuan earthquake and its aftershock sequence

We relocated M8.0 Wenchuan earthquake and 2706 aftershocks with M⩾2.0 using double-difference algorithm and obtained relocations of 2553 events. To reduce the influence of lateral variation in crustal and upper mantle velocity structure, we used different velocity models for the east and west side of Longmenshan fault zone. In the relocation process, we added seismic data from portable seismic stations close to the shocks to constrain focal depths. The precisions in E-W, N-S, and U-D directions after relocation are 0.6, 0.7, and 2.5 km respectively. The relocation results show that the aftershock epi-centers of Wenchuan earthquake were distributed in NE-SW direction, with a total length of about 330 km. The aftershocks were concentrated on the west side of the central fault of Longmenshan fault zone, excluding those on the north of Qingchuan, which obviously deviated from the surface fault and passed through Pingwu-Qingchuan fault in the north. The dominant focal depths of the aftershocks are between 5 and 20 km, the average depth is 13.3 km, and the depth of the relocated main shock is 16.0 km. The depth profile reveals that focal depth distribution in some of the areas is characterized by high-angle westward dipping. The rupture mode of the main shock features reverse faulting in the south, with a large strike-slip component in the north. Supported by the Basic Research Project of Institute of Geophysics, China Earthquake Administration (Grant No. DQJB08Z03)     

High-precision relocation of the aftershock sequence of the January 8, 2022, MS6.9 Menyuan earthquake

The 2022 Menyuan M_S6.9 earthquake, which occurred on January 8, is the most destructive earthquake to occur near the Lenglongling (LLL) fault since the 2016 Menyuan M_S6.4 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.     

Relocation of the 1998 Zhangbei-Shangyi earthquake sequence using the double difference earthquake location algorithm

Introduction On January 10, 1998, at 11h50min Beijing Time (03h50min UTC), an earthquake of ML=6.2 occurred in the border region between the Zhangbei County and Shangyi County of Hebei Province. In total 87 events with ML3.0 were recorded by Beijing Telemetry Seismic Network (BTSN) before March of 1999. Before relocation the preliminary hypocenters determined by BTSN showed an epicentral distribution of 25 km long and 25 km wide without any predominate orientation. The epicentral a…     

芦山MS7.0级地震余震序列重新定位及构造意义

利用四川省地震台网的震相数据和双差定位方法对芦山M_S7.0级地震及其余震序列进行了精确定位,根据余震分布确定了发震断层的位置和断层面的几何特征,并对余震活动进行了分析.结果显示,芦山M_S7.0级地震的震中位于30.28°N、102.99°E,震源深度为16.33 km.余震沿发震断层向主震两侧延伸,主要分布在长约32 km、宽约15~20 km、深度为5~24 km的范围内.地震破裂带朝西南方向扩展范围较大,东北方向略小,余震震级随时间迅速衰减.震源深度剖面清晰地显示出发震断层的逆冲破裂特征,推测发震断层为大川—双石断裂东侧约10 km的隐伏断层.该断层走向217°、倾向北西,倾角约45°,产状与大川—双石断裂相比略缓,它们同属龙门山前山断裂带的叠瓦状逆冲断层系.受发震断裂影响,部分余震沿大川—双石断裂分布,西北方向的余震延伸至宝兴杂岩体的东南缘,与汶川地震的破裂带之间存在50 km左右的地震空区,有可能成为未来发生强震的潜在危险区.     

2003年新疆巴楚—伽师地震序列的双差法重新定位研究

将近台记录和区域台网数据联合用于双差地震定位算法,对2003年新疆巴楚-伽师MS6.8强震后404个ML≥3.5余震序列进行双差法重新精确定位,并对其进行了理论上的可行性分析. 精定位后定位结果与传统定位方法的原始定位结果进行比较发现：（1）精定位后震中分布图像更加集中,与当地的烈度考察和震源机制解结果更加协调;（2）震源深度优势分布集中在15～25km以内,与当地存在深度为10km以上低速沉积层的地质构造情况相一致;（3）精定位后定位残差由原来的3.94s降为0.24s,水平向估算误差平均可控制在1.1km以内,垂直向估算误差平均可控制在2.4km.     

Relocation and seismogenic structure of the 1998 Zhangbei-Shangyi earthquake sequence

Introduction The January 10, 1998 Zhangbei-Shangyi, Hebei Province, earthquake has been the third large event of magnitude 6.0 and greater since the 1976 great Tangshan earthquake of magnitude 7.8 in the northern China (33皛42癗, 110皛124癊). Before this event, there were only two events of magnitude 6.0 and greater occurred in or around the Tangshan area since 1976: the M=6.9 Ninghe, Tianjin, earthquake of November 15, 1976 and the M=6.2 Hangu, Tianjin, earthquake of May 12, 1977. The …     

川西地区小震重新定位及其活动构造意义

使用双差地震定位法对川西地区1992～2002年的13367个小震进行重新定位, 初步分析了地震活动性与地表活动构造的关系及其揭示的构造信息. 重新定位后,地震活动沿活动断裂成线（带）状分布现象非常突出,呈现出与地表活动构造的密切关系：结构简单的单一走滑断层具有上宽下陡的花状结构特征,拉分盆地与逆断裂具有线性而发散的分布式结构特征,逆断裂之下还存在缺震层. 此外,沿活动断裂带地震活动还具有空间分段性,揭示出局部地段存在着隐伏活动断裂和可圈定为地震危险区的地震空区. 震源深度分布显示,川西高原在15～20km的深度范围内普遍存在厚度约5km的缺震层,以高温高压实验结果为基础,通过计算川西地区地壳强度表明,大约14～19km的深度范围花岗岩处于塑性流变状态,说明缺震层的出现具有地壳物质塑性变形基础.     

2014 年云南盈江Ms 6.1 地震震源机制研究

利用中国数字地震台网记录的区域宽频带波形,通过频率域和时间域多步反演,研究了2014年云南盈江Ms6.1地震基于点源模型的震源机制解和有限断层模型.考虑到使用不同的波形资料类型和简化的一维速度模型等因素对震源参数反演结果的影响,进行了大量的测试比较.结果表明,使用近震波形和本区域简化一维速度模型M1,波形拟合误差最小.基于点源模型的震源机制解显示此次地震发震断层面参数分别为:走向176°/倾角84°/滑动角-173°,表现为一次右旋走滑错动为主的事件.矩心在水平方向上位于震中(24.99°N,97.84.E)北东向约7km,最佳波形拟合矩心深度7km.平均总标量地震矩M0为7.56×1017N·m,计算成矩震级为Mw5.8.进一步模拟高达0.5Hz的高频波形,获得了盈江地震的有限断层模型,结果显示此次地震未表现出明显的破裂方向性.破裂半径约10km,整个破裂面积为267.2km2,平均滑动量约0.05m,破裂在5 s内释放了大多数能量.震后0～2s内,破裂以孕震点为中心向四周同时扩展,在深度7～ 17km内释放了部分能量.2s后,破裂朝断层面顶部和沿走向两侧进一步延伸,约5s后破裂基本停止.     

Accurate relocation of earthquakes in central-western China using the double-difference earthquake location algorithm

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.     

2017年精河6.6级地震余震序列重新定位和发震构造

采用双差定位方法,利用中国地震台网的数据对2017年8月9日精河6.6级地震的余震序列进行了重新定位。截至2017年8月14日16时,共获得209个余震的重新定位结果。结果显示,余震主要呈近EW向或NWW向分布,余震区长约50km,宽约17km。余震分布在主震的西侧,推断此次地震单侧破裂。余震震源深度为1～25km,其中,震级较大余震深度为8～17km。精河地震序列的余震活动随时间呈起伏状衰减,震后2天内比较活跃,此后出现较快衰减。随时间推移,余震区呈现中西部衰减慢、东部衰减快的特点。此次地震震中距2011年精河5.0级地震震中21km,相比2011年精河地震,其震源更深,震级更大,但震源机制解相近,均为逆冲型。结合区域构造背景分析认为,库松木契克山前断裂为此次地震发震构造的可能性较大。     

2014年三峡秭归M4.5、M4.7震群序列定位及震源区三维P波速度结构研究

采用双差层析成像方法,对2014年3月27日M4.7和3月30日M4.5秭归震群重定位显示:0～5 km深度层P波高速区分布在仙女山断裂北中段和九畹溪断裂北段,天阳坪断裂一带为低速区;8 km深度层高速区分布在九畹溪断裂东侧,仙女山断裂较低;11 km层高速区仅分布在高桥断裂和周家山—牛口断裂之间地带。在地震集中区的下方(即8～12 km处)存在分布较为稳定的低速区,较大地震事件主要分布在高速区或高低速区交界地带,低速区内则很少有地震分布。局部高速体的存在为岩石发生瞬间破裂提供了物质基础,其与低速体间的梯度带是发震构造常发育的区域。研究区内的仙女山断裂北段、九畹溪断裂正是在该梯度带内发育的两条活动断裂。本地震序列的自地表至5 km和5～10 km深度范围内均有大量破裂存在表明,浅层地震仍在水库渗透范围内,而深部地震则与流体渗透无关。此次地震活动同时存在水库诱发地震和构造地震存在。     

2017年西藏米林6.9级地震震源参数及其构造意义

北京时间2017年11月18日06时34分,西藏自治区林芝市米林县发生了M6.9级地震.地震位于印度板块向欧亚板块插入的东北犄角,是喜马拉雅造山带地壳缩短和构造旋转变形最为强烈的部位.本研究利用多种近震和远震台网记录的波形和到时数据,对该地震的震源位置和发震时刻进行重新确定.结果表明,地震震源深度为海平面以下7 km±2 km（或地表以下10 km±2 km）,经纬度为（29.87°N±0.01°N,95.02°E±0.01°E）.结合其他地球物理和地质学资料,我们推测该地震发生在NNW向西兴拉断裂带,南迦巴瓦构造结北东向的逆冲推覆和青藏高原东南向逃逸的侧向挤出是该地震发生的主要构造背景.

     

云南盈江5.8级地震应急行动及灾害特征

2011年3月10日云南盈江发生5.8级地震,地震造成重大人员伤亡和财产损失.震后,各级政府和地震部门立即启动应急预案,周密安排和部署各项应急处置和救灾行动.本文简要介绍了盈江5.8级地震的应急行动和灾害情况及特征.     

2012年9月7日彝良地震及余震序列双差定位研究

本文提出了时域多通道相关检测函数并用其计算波形互相关走时差数据,采用双差定位法对2012年9月7日云南彝良地震和余震序列共944个地震进行重定位,得到652个重定位事件,并与目录数据的结果进行了对比.本文采用了多个准则对走时差数据进行筛选,确保定位结果稳定可靠.得到MS5.7主震的震中为27.516°N,103.951°E,震源深度6.9 km;MS5.6主震的震中为27.543°N,104.023°E,震源深度7.27 km;重定位结果显示,地震序列紧缩为条带状并沿附近断裂走向分布,深度总体分布较重定位前变浅,集中分布在5~8 km,地震群出现轻微倾斜.东西向、南北向、深度和发震时刻的平均相对误差分别为55.2 m,43.0 m,186.7 m和0.01 s,走时残差16ms.研究表明:互相关数据的结果要优于目录数据;震源深度与速度模型存在较大的相关性;确定彝良—会泽断裂为本次彝良地震序列的发震构造.     

福建仙游震群重定位及序列特征分析

使用福建东南沿海地壳速度结构模型,利用双差定位方法(hypodd),对2010年8月—2013年12月福建仙游地区震群序列进行重新定位,讨论仙游震群序列的变化特征。定位结果显示,仙游震群序列主要围绕金钟水库蓄水区周缘活动,震源位置和深度表现出一定时空阶段性分布特征,并具有一定水库地震性质。