Spatio-temporal seismicity changes and high-resolution fault zone structures associated with recent large earthquakes in China

中国近期大地震的时空地震活动变化及高分辨率断裂带结构

• 批准号: 1447091
• 负责人: Zhigang Peng
• 金额: $ 26.01万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1447091&HistoricalAwards=false
• 关键词: Spatio; temporal; seismicity; changes; resolution

Large earthquakes occur on major fault zones. Obtaining spatio-temporal changes of seismic activities and detailed fault zone properties around the times of large earthquakes are long-sought goals in earthquake seismology. Sometimes large shallow earthquakes are preceded by increased seismic activity also known as ?foreshocks?. However, the exact relationship among foreshocks, mainshock nucleation and fault zone structures are still in debate. Recently several large earthquakes occurred around the Tibetan Plateau in China, and produced significant damages and casualties. These include the 2008 Ms7.3 Yutian, Ms8.0 Wenchuan, the 2010 Ms7.0 Yushu, the 2013 Ms7.0 Lushan, and the 2014 Ms7.3 Yutian earthquakes. Among them, the Yushu and Yutian mainshocks had clear evidence of M4-5 foreshocks, while the Wenchuan and Lushan mainshocks did not., a comprehensive analysis could provide us a better understanding on whether foreshocks exist and their physical mechanisms. This project will support a team to conduct a systematic examination of seismicity changes around the times of these large earthquakes in China, as well as high-resolution imaging of fault zone structures. The study will employ continuous waveforms recorded by permanent seismic stations around the region of each mainshock, as well as dense aftershock deployment. To examine evolutionary changes in seismicity and fault zone processes, the researchers plan to conduct the following tasks: (1) Use a recently developed waveform matched filter technique to detect all earthquakes long before the occurrence of each mainshock; (2) Use newly relocate catalogs to search for spatio-temporal evolutions before mainshock, as well as performing Epidemic Type Aftershock Sequence (ETAS) modeling and deriving source properties; (3) Identify fault zone head waves along the rupture zones of several recent events; and (4) Perform joint inversion of P and FZHWs for high-resolution fault interface properties. With multi-facet techniques and extensive waveform data, they look to obtain a more complete picture on evolutions of seismic activities and their relationship with fault zone processes around the epicenters of several large intra-plate earthquakes in China. This project can provide important new evidence on the existence (or lack of) precursory changes that precede large mainshocks. The obtained results are essential for evaluating the use of foreshocks as forecasting tools and seismic hazard mitigation in these regions. The project will develop data products such as newly detected earthquake catalog and share with other researchers via peer-reviewed publications. This project will support both graduate students and undergraduate interns to conduct scientific research in China, and promote international collaboration. The project is co-supported by the ISE Global Venture Fund.

大地震发生在主要断裂带上。获取大地震前后地震活动的时空变化和详细的断裂带特征是地震学长期追求的目标。有时，大浅层地震之前会出现地震活动增加，也称为“前震”。然而，前震、主震成核与断裂带结构之间的确切关系仍存在争议。近期，我国青藏高原周边发生多起特大地震，造成重大损失和人员伤亡。其中包括2008年玉田7.3级地震、汶川8.0级地震、2010年玉树7.0级地震、2013年庐山7.0级地震和2014年于田7.3级地震。其中，玉树和玉田主震有明显的M4-5级前震证据，而汶川和芦山主震则没有。综合分析可以帮助我们更好地了解前震是否存在及其物理机制。该项目将支持一个团队对中国这些大地震前后的地震活动变化进行系统检查，并对断层带结构进行高分辨率成像。该研究将采用每次主震区域周围永久地震台记录的连续波形以及密集的余震部署。为了研究地震活动和断层带过程的演化变化，研究人员计划开展以下任务：（1）使用最近开发的波形匹配滤波技术来检测每次主震发生之前很久的所有地震； （2）利用新迁移的目录搜索主震前的时空演化，并进行流行型余震序列（ETAS）建模并推导震源属性； (3) 识别最近发生的几次事件中沿着破裂带的断层带头波； (4) 对 P 和 FZHW 进行联合反演以获得高分辨率断层界面属性。通过多方面的技术和广泛的波形数据，他们希望获得关于地震活动演化及其与中国几次大型板内地震震中周围断裂带过程的关系的更完整的图景。该项目可以提供重要的新证据，证明大型主震之前是否存在（或缺乏）前兆变化。获得的结果对于评估这些地区使用前震作为预报工具和减轻地震灾害至关重要。该项目将开发新检测到的地震目录等数据产品，并通过同行评审的出版物与其他研究人员分享。该项目将支持研究生和本科生实习生在中国开展科学研究，并促进国际合作。该项目得到了ISE全球风险基金的共同支持。