Investigating spatiotemporal changes in crustal stress associated with major earthquakes has implications for understanding seismogenic processes.However,in individual earthquake cases,the characteristics of the stres...Investigating spatiotemporal changes in crustal stress associated with major earthquakes has implications for understanding seismogenic processes.However,in individual earthquake cases,the characteristics of the stress after it reaches its maximum value are rarely discussed.In this study,we use the 2021 M_S6.4 Yangbi earthquake in Yunnan,China and events of magnitudes M_L≥3.0 occurred in the surrounding area in the previous 11 years to investigate the spatiotemporal evolution of apparent stress.The results indicate that apparent stress began to increase in January 2015 and reached a maximum in January 2020.Apparent stress then remained at a high level until October 2020,after which it declined considerable.We suggest that the stress was in the accumulation stage from January 2015 to January 2020,and entered the meta-instability stage after October 2020.During the meta-instability stage,the zone of decreasing stress expanded continuously and the apparent stress increased around the Yangbi earthquake source region.These features are generally consistent with the results of laboratory rock stress experiments.We propose that apparent stress can be a good indicator for determining whether the stress at a specific location has entered the meta-instability stage and may become the epicenter of an impending strong earthquake.展开更多
2021年5月21日21时,云南大理白族自治州漾濞县发生M_(S)6.4地震。该地震的震中位于川滇块体的西南边界,是该区40多年来震级最大的一次地震。地震未产生地表破裂,余震也未沿震区附近已知的断裂分布。研究者针对这次地震的发震构造已有若...2021年5月21日21时,云南大理白族自治州漾濞县发生M_(S)6.4地震。该地震的震中位于川滇块体的西南边界,是该区40多年来震级最大的一次地震。地震未产生地表破裂,余震也未沿震区附近已知的断裂分布。研究者针对这次地震的发震构造已有若干研究结果,但采用不同数据、方法和思考角度对这些结果进行验证并同时补充新认识是必要的。文中利用云南地震台网观测资料分析了漾濞地震序列的时空分布特征,进行重新定位,并通过CAP(Cut and Paste)方法获取序列中较大地震的震源机制解与矩心深度。结果表明,漾濞地震的余震震源深度主要集中在4~13km,余震带总体呈NW-SE走向,空间分段性明显:主震震中北西侧余震稀少且分布相对集中,东南侧余震密集且余震带宽度变大;前震序列发生在主震震中的东南侧,与余震密集段的位置基本重叠,反映主震震中北西侧的稀疏余震应属于触发型,而主震破裂可能属于由震中向SE扩展的单侧破裂型。余震带的深度横剖面显示主震破裂具有明显的分段性,序列北西段的结构较为简单,显示出一个地震丛集,而南东段则相对复杂,很可能由2条倾向SW的高倾角断层组成。漾濞地震序列中29个M_(S)≥3.0地震的矩心深度主要分布于3~13km,震源机制解以右旋走滑型为主,大多存在一个NW-SE走向的高倾角节面,且具有一定的正断倾滑分量。主震是以右旋走滑为主的破裂所引发的,矩心深度为5.2km,与重定位所得的震源初始破裂深度8.9km较为接近,反映该地震发生在上地壳,也反映震区的地震活动深度偏浅。文中对2021年5月云南漾濞序列的时-空分布特征与震源机制解的分析,反映此次地震的发震断层产状及力学性质与NW走向的维西-乔后-巍山断裂较为一致,但位置不同,证实这次地震的发震构造是该断裂南段西侧一条SW陡倾的右旋走滑次级断裂。展开更多
基金partially supported by the research grants from Spark Program of Earthquake Sciences(XH213703Y)National Institute of Natural Hazards,Ministry of Emergency Management of China(No.ZDJ2020-09 and No.ZDJ2019-16).
基金supported by the China National Key R&D Program (No.2018YFC1503305)the Special fund of the Institute of Geophysics,China Earthquake Administration (No.DQJB22Z04)。
文摘Investigating spatiotemporal changes in crustal stress associated with major earthquakes has implications for understanding seismogenic processes.However,in individual earthquake cases,the characteristics of the stress after it reaches its maximum value are rarely discussed.In this study,we use the 2021 M_S6.4 Yangbi earthquake in Yunnan,China and events of magnitudes M_L≥3.0 occurred in the surrounding area in the previous 11 years to investigate the spatiotemporal evolution of apparent stress.The results indicate that apparent stress began to increase in January 2015 and reached a maximum in January 2020.Apparent stress then remained at a high level until October 2020,after which it declined considerable.We suggest that the stress was in the accumulation stage from January 2015 to January 2020,and entered the meta-instability stage after October 2020.During the meta-instability stage,the zone of decreasing stress expanded continuously and the apparent stress increased around the Yangbi earthquake source region.These features are generally consistent with the results of laboratory rock stress experiments.We propose that apparent stress can be a good indicator for determining whether the stress at a specific location has entered the meta-instability stage and may become the epicenter of an impending strong earthquake.
文摘2021年5月21日21时,云南大理白族自治州漾濞县发生M_(S)6.4地震。该地震的震中位于川滇块体的西南边界,是该区40多年来震级最大的一次地震。地震未产生地表破裂,余震也未沿震区附近已知的断裂分布。研究者针对这次地震的发震构造已有若干研究结果,但采用不同数据、方法和思考角度对这些结果进行验证并同时补充新认识是必要的。文中利用云南地震台网观测资料分析了漾濞地震序列的时空分布特征,进行重新定位,并通过CAP(Cut and Paste)方法获取序列中较大地震的震源机制解与矩心深度。结果表明,漾濞地震的余震震源深度主要集中在4~13km,余震带总体呈NW-SE走向,空间分段性明显:主震震中北西侧余震稀少且分布相对集中,东南侧余震密集且余震带宽度变大;前震序列发生在主震震中的东南侧,与余震密集段的位置基本重叠,反映主震震中北西侧的稀疏余震应属于触发型,而主震破裂可能属于由震中向SE扩展的单侧破裂型。余震带的深度横剖面显示主震破裂具有明显的分段性,序列北西段的结构较为简单,显示出一个地震丛集,而南东段则相对复杂,很可能由2条倾向SW的高倾角断层组成。漾濞地震序列中29个M_(S)≥3.0地震的矩心深度主要分布于3~13km,震源机制解以右旋走滑型为主,大多存在一个NW-SE走向的高倾角节面,且具有一定的正断倾滑分量。主震是以右旋走滑为主的破裂所引发的,矩心深度为5.2km,与重定位所得的震源初始破裂深度8.9km较为接近,反映该地震发生在上地壳,也反映震区的地震活动深度偏浅。文中对2021年5月云南漾濞序列的时-空分布特征与震源机制解的分析,反映此次地震的发震断层产状及力学性质与NW走向的维西-乔后-巍山断裂较为一致,但位置不同,证实这次地震的发震构造是该断裂南段西侧一条SW陡倾的右旋走滑次级断裂。
