Collaborative Research: Deformation Processes in the Andaman-Nicobar Islands

合作研究：安达曼-尼科巴群岛的变形过程

• 批准号: 0809954
• 负责人: Anthony Lowry
• 金额: $ 6万
• 依托单位: Utah State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0809954&HistoricalAwards=false
• 关键词: Collaborative; Research; Deformation; Processes; Andaman

The December 2004 Sumatra-Andaman earthquake was the second largest (Mw 9.3) and second deadliest (~280,000 casualties) earthquake ever recorded. It was also unusual in that it combined a normal ?fast? rupture with a more unusual slow fault slip event. This unique occurrence presents an important opportunity to examine two questions with potentially wide-ranging implications for global earthquake studies: (1) What processes and rheologies re-equilibrate stress following great earthquakes in island arc settings? And (2) What Earth properties control the speed of rupture in great earthquakes? The boundary between the Indian and Andaman tectonic plates is almost entirely submarine, but the Andaman-Nicobar Island group enables a revealing look at postseismic deformation in the segment that ruptured principally as a slow earthquake and hence generated relatively little ground shaking. The investigators on this project are continuing to capture postseismic deformation after the Sumatra-Andaman earthquake by operating a network of 14 Global Positioning System (GPS) sites in the Andaman-Nicobar Islands. The network currently consists of 4 continuous and 10 campaign sites. These ?ground-truth? geodetic data (from a locale where data acquisition is notoriously difficult) are being combined with satellite measurements of gravity and shoreline changes to examine key scientific questions about the deformation and stress cycle on a subduction thrust that exhibited unusual slow slip behavior during one of the largest earthquakes of the past century. Modeling of the first several years of GPS postseismic displacements indicates slip down-dip of the seismic rupture dominated near-field deformation during that period. Modeling suggests the early fault slip response is now completed and that mantle flow will dominate near-field deformation for the next several years. The network is designed to capture these viscoelastic flow signals, to fingerprint any continuing fault slip that may illuminate slip stability of the shallow plate-bounding thrust, and to assess whether time- and space-dependent nonlinear effects of power-law creep rheology are in evidence. Slip stability in particular is being assessed by examining the data for evidence of nonlinear fault slip (so-called ?slow slip events?) on the shallow plate boundary that ruptured during the earthquake. The rock flow process is also being examined for evidence of a different type of nonlinearity that is expected based on laboratory rock deformation experiments, but that has not been observed unequivocally in the real Earth. University of Memphis investigators are operating the GPS network in partnership with the Indian Institute of Science, Bangalore and the Society of Andaman & Nicobar Ecology (SANE). Modeling and interpretation combines the expertise of investigators at the University of Memphis and Utah State University (USU). Deformation processes that re-equilibrate stress following large earthquakes are intrinsically linked to the processes that accumulate stress leading up to large earthquakes, so this ongoing investigation will illuminate the physics of earthquake slip and the earthquake cycle globally

2004年12月的苏门答腊-安达曼地震是有记录以来第二大地震（里氏9.3级）和第二大致命地震（约28万人伤亡）。它的不寻常之处在于，它结合了正常？快速？伴随着更不寻常的缓慢断层滑动事件的破裂。这一独特的事件提供了一个重要的机会来研究两个问题，这些问题可能对全球地震研究产生广泛的影响：(1)在岛弧环境中，什么过程和流变学重新平衡了大地震后的应力？(2)什么地球特性控制了大地震的破裂速度？印度和安达曼构造板块之间的边界几乎完全是在海底，但安达曼-尼科巴群岛群可以揭示地震后变形的部分，主要是由于缓慢的地震而破裂，因此产生的地面震动相对较小。该项目的研究人员通过在安达曼-尼科巴群岛运行一个由14个全球定位系统（GPS）站点组成的网络，继续捕捉苏门答腊-安达曼地震后的形变。该网络目前由4个连续和10个竞选网站组成。这些真实?大地测量数据（来自一个数据采集非常困难的地区）正在与重力和海岸线变化的卫星测量相结合，以研究有关俯冲逆冲的变形和应力循环的关键科学问题，该俯冲逆冲在上个世纪最大的地震之一中表现出不寻常的慢滑行为。对前几年GPS地震后位移的模拟表明，在这一时期，地震破裂主导了近场变形的滑动下倾。模拟表明，早期断层滑动响应现在已经完成，地幔流将在未来几年主导近场变形。该网络旨在捕捉这些粘弹性流动信号，识别任何可能阐明浅板块边界逆冲滑动稳定性的连续断层滑动，并评估幂律蠕变流变学的时间和空间相关非线性效应是否存在。特别是滑动稳定性是通过检查非线性断层滑动(所谓的？缓慢滑动事件？)在地震中破裂的浅板块边界上。岩石流动过程也正在被研究，以寻找一种不同类型的非线性的证据，这种非线性是基于实验室岩石变形实验所期望的，但在真实的地球上并没有明确观察到。孟菲斯大学的研究人员正在与班加罗尔的印度科学研究所和安达曼尼科巴生态学会（SANE）合作运营GPS网络。建模和解释结合了孟菲斯大学和犹他州立大学（USU）研究人员的专业知识。大地震后重新平衡应力的变形过程与导致大地震的应力积累过程有着内在的联系，因此这项正在进行的研究将阐明地震滑动的物理学和全球地震周期