Study of Coseismic Damage and Post-mainshock Healing on the Longmen-Shan Fault Ruptured in the 2008 M8 Wenchuan Earthquake in China

2008年汶川8级地震龙门山断裂带同震破坏及主震后修复研究

• 批准号: 0910911
• 负责人: Yong-Gang Li
• 金额: $ 10.86万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0910911&HistoricalAwards=false
• 关键词: Study; Coseismic; Damage; Post; mainshock

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5) The Longmen-Shan Fault (LSF) located at the east margin of the Tibetan Plateau in western China is featured by active tectonics. It was broken in total length of 300 km with the maximum slip larger than 9 m in the devastating M8 Wenchuan earthquake on May 12, 2008. Its rupture length, slip and magnitude are comparable with those of the 1857 and 1906 big earthquakes in California. The PI and student will study the co-seismic rock damage and post-mainshock healing on the LSF associated with this M8 earthquake using the data recorded at the Sichuan Seismic Network (SSN) stations and portable seismographs deployed at the ruptures after the Wenchuan earthquake. We shall identify clusters of repeated earthquakes among more than ten thousands of Wenchuan aftershocks and use the waveform data from them to measure temporal changes in seismic velocity caused by the Wenchuan earthquake. They will also delineate the subsurface structure of the low-velocity damage zone on the LSF using fault-zone trapped waves generated by aftershocks recorded at near-fault stations. The results from the Longmen-Shan Fault will be compare to those obtained from our previous studies for the process of rock damage and heal at the Parkfield San Andreas Fault and rupture zones of the 1992 M7.4 Lands and 1999 M7.2 Hector Mine earthquakes.Because of the density of the data recorded at the Sichuan Seismic Network for the pre-shock and aftershock sequence of the 2008 M8 Wenchuan earthquake, this study will be one of a few cases to illuminate the in-situ fault-zone rock damage and healing at seismogenic depths associated with a big M8 earthquake. The wealth of unexpected data from the M8 Wenchuan earthquake will improve the resolution in our study of the spatio-temporal variations in properties of the active faults and the depth extent of the damage zone. The spatial extent of fault-zone damage and the loss and recouping of strength across the earthquake cycle are critical ingredients in understanding of fault mechanics and physics. With a comparison of big earthquakes in China with those in US, the most basic information on the in-situ state of the fault zone aids the understanding of earthquake processes and hazards globally. The proposed work will allow us to determine the evolution of fault-zone physical properties with a big earthquake, document characteristics of damaging earthquakes and help us to evaluate potential earthquake risk in seismogenic regions in USA and China. This research project on the M8 Wenchuan earthquake will be carried out under the Sino-US Earthquake Study Protocol. The project will involve post-doctoral and graduate researcher.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）的龙门山断层（LSF）位于中国西部青藏高原东缘，具有活动构造的特点。在2008年5月12日汶川8级特大地震中，断裂全长300 km，最大滑动量超过9 m。其破裂长度、滑动量和震级与1857年和1906年加州大地震相当。PI和学生将使用四川地震台网（SSN）台站记录的数据和汶川地震后部署在破裂处的便携式地震仪，研究与这次M8地震相关的LSF的同震岩石破坏和主震后愈合。我们将从汶川地震的上万次余震中识别出重复地震群，并利用它们的波形数据来测量汶川地震引起的地震速度的时间变化。他们还将利用近断层台站记录的余震产生的断层带陷波来描绘LSF上低速破坏区的地下结构。将龙门山断层的结果与我们以前在帕克菲尔德圣安德烈亚斯断层和1992年7.4级陆地地震和1999年7.2级赫克托矿地震破裂带的岩石损伤和愈合过程的研究结果进行比较。通过对2008年汶川8级地震的地震和余震序列的研究，本研究将成为阐明8级大地震在孕震深度的原地断裂带岩石损伤和愈合的少数案例之一。汶川8级地震的丰富的突发性资料将提高我们研究活动断裂性质和破坏带深度的时空变化的分辨率。断层带破坏的空间范围以及地震周期中强度的损失和恢复是理解断层力学和物理学的关键因素。通过中美大地震的对比，了解断裂带的最基本的原位状态有助于了解全球地震过程和灾害。建议的工作将使我们能够确定断层带的物理性质与大地震的演变，文件破坏性地震的特点，并帮助我们评估潜在的地震风险在美国和中国的孕震区。本次汶川8级地震研究项目将在中美地震研究协议框架下进行。该项目将涉及博士后和研究生研究人员。