摘要
2017年8月8日21时19分在我国四川省北部阿坝州九寨沟县发生了M_W6.5左旋走滑型地震.该地震发生在青藏高原巴颜喀拉块体东北缘,东昆仑断裂南东段的塔藏断裂、岷江断裂和虎牙断裂的交汇地带.包括此次地震,近年来在巴颜喀拉块体周缘已发生了九次6级以上强震,表明巴颜喀拉块体周缘主要活动断裂上的应力水平仍处于不断调整之中.本文采用库仑应力模型研究2017年M_W6.5九寨沟地震激发的库仑应力变化、该地震与周边地震的应力触发关系以及强震对周边主要活动断裂的应力扰动.强震序列包括周边区域1536—1975年M≥6历史强震和1976—2017年的M_W≥6 gCMT地震目录中的强震,共计32个.研究结果表明:(1)2017年M_W6.5九寨沟地震激发的同震库仑应力变化仅在局部范围内超过0.1×10~5Pa,且75%的余震(～12.7天)受到该地震明显的同震应力触发作用,而其余25%的余震落在应力影区,采用最优破裂面可以进一步提高同震库仑应力变化与余震分布的空间相关性;(2)2008年M_W7.9汶川地震对2017年M_W6.5九寨沟地震的发生有一定的促进作用,在后者震源处激发的同震库仑应力变化为(0.026～0.263)×10~5Pa,震后黏弹性库仑应力变化为(0.010～0.032)×10~5Pa.该库仑应力的变化范围取决于汶川地震源断层参数和九寨沟地震接收断层参数.2013年M_W6.6芦山地震对九寨沟地震的发生几乎没有影响(<0.001×10~5Pa);(3)1654年M8.0甘肃天水南地震对九寨沟地震的发生有明显的促进作用,在九寨沟地震震源处激发的同震库仑应力变化为(0.410～1.266)×10~5Pa,震后库仑应力变化为(0.147～0.490)×10~5Pa.1879年M8.0甘肃武都地震可能有比1654年M8.0甘肃天水南地震更强的应力触发作用,但也有可能对九寨沟地震的发生起到抑制作用.在选取的8个九寨沟地震接收断层面上,其中6个接收断层面上该地震所激发的同震库仑应力变化为(0.913～2.364)×1
At 21：19 PM, 8 August 2017 （local time） a MW6.5 sinistral strike-slip earthquake （hereinafter termed the Jiuzhaigou earthquake） struck at the Jiuzhaigou county, Sichuan province, China. This strong earthquake occurred in the proximity of the northeast rim of the Bayan Har block on the Tibetan Plateau. Locally, it took place at the confluence zone of the Tazang fault to the north that is the southeastern segment of the NW Eastern Kunlun fault, the NS Minjiang fault to the west and the NW Huya fault to the south. Apart from the Jiuzhaigou earthquake, over the past twenty years there have occurred eight MW≥6 strong earthquakes along the periphery of the Bayan Har block, suggesting that stress levels on major active faults bounding the Bayan Har block have been being adjusted profoundly. In this paper, we use the Coulomb failure model to explore the Coulomb stress triggering effects in terms of mainshock-aftershock triggering, mainshock-mainshock triggering, and mainshock-fault interplay, so as to understand the relations between the Jiuzhaigou earthquake and its aftershocks, whether the Jiuzhaigou earthquake was triggered or promoted by the 2008 MW7.9 Wenchuan earthquake or 2013 MW6.6 Lushan earthquake and to what extent the surrounding major faults were loaded or unloaded. We consider additional 31 surrounding MW≥6 earthquakes comprising 19 historic earthquakes from 1536 to 1975 and 12 other MW≥6 earthquakes from the gCMT catalog from 1976 to 2017. Our results indicate that： （1） The Jiuzhaigou earthquake aroused significant Coulomb stress changes （larger than 0.1×105Pa） merely in a local region. In addition, 75% of the total 1867 relocated aftershocks with relocation precision less than 0.7 km during the approximately 12.7 days lay in stress triggering zones on a profile where the source fault is included, whereas the remaining 25% still took place in stress shadows. The inconsistency between the spatial patterns of these aftershocks and coseismic Coulomb stress changes can be reconciled
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2017年第11期4398-4420,共23页
Chinese Journal of Geophysics
基金
国家重点基础研究发展计划(973计划)项目(20-13CB733303)
国家自然科学基金重点项目(41431069)
国家自然科学基金项目(41574002
41474019)联合资助
