Collaborative Research: High-Precision Teleseismic Relocation and Tomography for the M 9 and M 8.7 Sumatra Great Earthquake Sequences

合作研究：苏门答腊岛9级和8.7级大地震的高精度远震重定位和层析成像

• 批准号: 0609535
• 负责人: Michael Brudzinski
• 金额: $ 2.26万
• 依托单位: Miami University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0609535&HistoricalAwards=false
• 关键词: Collaborative; Research; Precision; Teleseismic; Relocation

The seismic and tsunami hazard posed by great subduction zone earthquakes has long been recognized, but in light of the December 26, 2004 Mw 9+ Sumatra-Andaman Islands earthquake, the resulting tsunami, infrastructure damage and huge loss of life, it is clear that the danger posed by such events remains underestimated. The Sumatra great earthquake is one of the four largest events in the instrumental record, comparable in many respects to the 1960 Mw 9.5 Chilean and 1964 Mw 9.2 Alaska subduction megathrust events that generated significant damage and tsumani within the Pacific ocean basin. The Sumatra-Andaman Islands event triggered a second great earthquake, the March 28, 2005 Mw 8.7 Nias event, directly to the south, increasing concerns about the occurrence of a third great earthquake offshore southern Sumatra in the near-term. This study consists of a series of high-precision earthquake relocation of the 2004 and 2005 Sumatra aftershock sequences and prior regional seismicity and computation of compressional and shear seismic wave speeds in three-dimensions for the Sumatra region in order to better constrain how thermal, mechanical, compositional, hydrological, and rupture processes interact along subduction megathrusts during great earthquakes. The 2004 and 2005 main shock and aftershock sequences generated over 5000 earthquakes recorded globally by seismic networks along 1700 km of subduction system. In the Sumatra region, however, the seismogenic portion of the subduction megathrust lies primarily within an oceanic environment, which ultimately limits the amount and coverage of local and regional seismic data that will become available, and emphasizes the need for state-of-the-art analysis of the available global data. The increased precision earthquake catalog is used to refine subduction zone geometry and to explore spatio-temporal variability within and between the aftershock series. Comparisons between aftershocks and prior regional seismicity provide insight into processes within the subduction zone leading up to these great earthquakes, while comparisons between compressional and shear wave speed models and regional seismicity patterns can be related to variations in rupture behavior along the subduction megathrust. The study builds over three stages: 1) probabilistic phase re-determination, waveform cross-correlation of phases to reduce picking error, and single-event earthquake relocations using the Engdahl, van der Hilst, and Buland method, 2) high-precision relative earthquake locations using teleseismic double-difference methods, and 3) inversion for regional compressional and shear wave speed models in three dimensions using teleseismic DD tomography methods. Among the broader impacts are: 1) The methods developed significantly advance the use of global catalog and waveform data to study regional-scale problems where high spatial density local seismometer deployments are not feasible, and all techniques are shared with the public; 2) Data analysis and interpretation involves undergraduate, graduate, and young investigator collaboration with well-established experts in the fields of earthquake location and tomography; and 3) The project involves five institutions, including the Institut Teknologi Bandung, and strengthens ties with the scientific community in Indonesia.

长期以来，大俯冲区地震带来的地震危害和海啸危害已得到认可，但鉴于2004年12月26日MW 9+苏门答腊 - 安达曼群岛地震，最终的海啸，基础设施损害和巨大的生活损失，很明显，这些事件构成了这些事件的危险。苏门答腊大地震是工具记录中的四个最大事件之一，在许多方面与1960 MW 9.5智利和1964 MW 9.2阿拉斯加俯冲Megathrust事件相当，在太平洋海洋盆地内造成了重大损害和Tsumani。苏门答腊 - 安达曼群岛的事件引发了第二次大地震，即2005年3月28日，MW 8.7 NIAS事件，直接向南，对在近期发生的第三次大地震近海苏门答腊岛的发生越来越担心。这项研究包括一系列对2004年和2005年苏门答腊余震序列以及先前的区域地震序列以及苏门答腊区域三维压缩和剪切地震波速的计算的高精度地震迁移，以便更好地限制热量，机械，组合物，水文和破裂的过程中的热量，以更好地限制如何限制热量。 2004年和2005年的主要冲击和余震序列沿俯冲系统沿1700 km的地震网络在全球播放了5000多个地震。然而，在苏门答腊区域中，俯冲的地震部分主要位于海洋环境中，这最终限制了将可用的局部和区域地震数据的数量和覆盖范围，并强调了对可用全球数据进行最新分析的需求。提高的精确地震目录用于改进俯冲带的几何形状，并探索余震序列内和之间的时空变异性。余震与先前的区域地震性之间的比较提供了对俯冲区域内的过程的洞察力，导致这些巨大地震，而压缩和剪切波速度模型和区域地震性模式之间的比较可能与俯冲Megathrust沿俯冲沿线的破裂行为的变化有关。 该研究建立了三个阶段：1）概率的相位重新确定，波形的阶段的波形互相关以减少采摘误差，以及使用Engdahl，van der Hilst和Buland方法进行单事地震重新定位，2）使用远距离抗抗性的方法和3）dimiression shoptions和3）dimiression shoptions和3）远距离DD断层扫描方法。 更广泛的影响是：1）所开发的方法可显着提高全球目录和波形数据的使用来研究高空间密度局部地震计的部署不可行的区域尺度问题，并且与公众共享所有技术； 2）数据分析和解释涉及与地震地点和层析成像领域的良好专家的本科，研究生和年轻的研究者合作； 3）该项目涉及五个机构，包括Teknologi Bandung研究所，并加强了与印度尼西亚科学界的联系。