2019年四川长宁6.0级地震序列时空演化特征及其地震构造环境研究

doi:10.12196/j.issn.1000-3274.2020.04.007

摘要/Abstract

摘要： 地震序列类型能够直观地反映构造应力场环境、地震构造及孕震环境介质的差异性。主—余型地震多发生在相对均匀的介质环境, 而前—主—余型地震及震群型地震往往发生在复杂的构造环境。 2019年6月17日四川省宜宾市长宁县发生的6.0级地震余震活动总体呈NW向分布, 其南东段的余震呈相对单一的NW向条带状, 而北西段的余震活动呈现丛集的特征。两段的地震序列类型也表现出明显的差异性, 南东段地震序列为主—余型, 序列衰减速度较快; 北西段地震序列为震群型, 序列初期衰减非常缓慢, 余震丰富。此次6.0级地震序列发生在长宁—双河大背斜上, 该复式背斜主要由多个次级褶皱构造和不同走向的伴生断层组成, 结构复杂。长宁6.0级地震序列的分段性特征表明, 该地震序列不是发生在单一的断裂构造上, 为多个构造级联破裂所导致的复合型地震序列。此外, 序列北西段余震的深度逐渐变深, 可能预示着该区域受华蓥山断裂带活动的影响, 地震序列对华蓥山断裂带未来地震活动的影响应引起关注。

关键词: 2019年长宁6.0级地震, 地震序列, 构造环境

Abstract: Features of seismic sequence can directly reflect the differences among tectonic stress field, seismotectonic and seismogenic environment. For example, mainshock-aftershock-type earthquakes mostly occur in a relatively uniform medium environment. However, foreshock-mainshock-aftershock-type earthquakes and swarms mainly occur in complex structure. On 17 June, 2019, the M6.0 an earthquake occurred in Changning County, Yibin City, Sichuan Province. Its aftershock totally distributed along a NW direction belt, bit in the northwest part of the belt, the aftershock distribution showed the cluster features. There is an obvious difference between the southeast part and northwestern part for aftershock activity. The southeast part can be considered as a mainshock-aftershock type with a fast decay. The northwestern part shows a feature of swarm, which decay is slowly and many aftershocks with M5 or more in the early stage. The M6.0 earthquake occurred in the Changning-Shuanghe anticline which is complicated and composed of several secondary fold structures and associated faults. The segmentation characteristics of the Changning M6.0 earthquake indicate that it is hardly to be produced by a single fault but a cascade fractures. Moreover, the aftershock focal depths in the northwestern part are more deeply, this means that the seismic activity in this area has been controlled by the Huaying Shan fault zone. Oppositely, the possible influence of the 2019 Changning M6.0 earthquake on Huaying Shan fault zone should be emphasized in the future.

Key words: The 2019 Changning M6.0 earthquake, Seismic sequence, Tectonic environment

中图分类号:

P315.7

宫悦, 王宇玺, 梁明剑, 龙锋, 赵敏. 2019年四川长宁6.0级地震序列时空演化特征及其地震构造环境研究[J]. 地震, 2020, 40(4): 90-102.

GONG Yue, WANG Yu-xi, LIANG Ming-jian, LONG Feng, ZHAO Min. Study on the Spatio-temporal Evolution Characteristics and Seismic Structure Environment of the 2019 M6.0 Changning Sichuan Earthquake Sequence[J]. EARTHQUAKE, 2020, 40(4): 90-102.

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