Collaborative research: Unraveling coseismic and postseismic deformation: A prerequisite for analyses of stress-coupling and tsunami genesis.

合作研究：揭示同震和震后变形：分析应力耦合和海啸成因的先决条件。

• 批准号: 1264288
• 负责人: Timothy Masterlark
• 金额: $ 13.12万
• 依托单位: South Dakota School of Mines and Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1264288&HistoricalAwards=false
• 关键词: Collaborative; research; Unraveling; coseismic; postseismic

The December 26, 2004 M9.2 Sumatra-Andaman Earthquake (SAE), the third largest earthquake ever recorded, ruptured the boundary separating the subducting Indo-Australian Plate from the overriding Burma Plate and triggered a devastating tsunami that significantly impacted 9 countries bordering the Indian Ocean. Near the epicenter, the tsunami caused over 30 meters of run-up in some coastal areas of Northern Sumatra, almost instantly killing over 200,000 people. The rupture of the SAE included more than 20 meters of fault-slip, based on associated seismologic data and GPS measurements of seafloor and ground deformation. This magnitude of deformation provides a rare opportunity to conduct a regional-scale in-situ rheological experiment, in which the coseismic fault-slip is the impulse and the subsequent deformation is the response. Modeling these measured perturbations can test hypotheses of coseismic (including tsunami-genesis) and postseismic (including earthquake-coupling and tsunami run-up) behavior. Specifically, Finite Element Models (FEMs) of the subduction zone near the epicenter allow for a quantitative evaluation of the role of rheologic partitioning and processes, on the stress, strain, and pore pressure that govern coseismic and postseismic behavior. Tsunami propagation models can then use FEM-generated seafloor deformations to predict coastal run-up. This modeling and interpretive study of the SAE will address the following scientific questions: (1) How does the distribution of material properties (i.e., structure, density, porosity, and stiffness of rock formations in the subduction zone) affect fault-slip estimations ? (2) How does this distribution influence seafloor deformation, tsunami genesis, and run-up predictions ? (3) What is the timing and distribution of poroelastic and viscoelastic postseismic deformation ? (4) What afterslip is required ? (5) Do Coulomb stress and pore pressure transients correlate to aftershock occurrence ? These questions are underpinned by a more fundamental question: How do we construct and constrain models of coseismic and postseismic behavior as a synthesis of processes, all of which contribute to the deformational system ? Accordingly, the primary goal of the proposed research is to determine the distribution and calibration of rheologic properties that describe coseismic and postseismic behavior of the SAE. More specifically, FEM simulations will address aftershock occurrence in both space and time (including stress-coupling between the SAE and the March 25, 2005 M8.7 Nias earthquake that occurred 350 km away from the SAE epicenter). FEM-generated seafloor deformation predictions will drive tsunami propagation simulations. Because we expect that variations in material properties (and possibly secondary splay faulting) will cause both long and shorter scale seafloor deformations, tsunami generation and propagation simulations will be performed with the dispersive long wave model FUNWAVE. Tsunami hazards will be expressed in terms of simulated run-up and inundation for the most affected areas of the Indian Ocean (e.g., Northern Sumatra), and compared to the observed impact of the 12/26/04 tsunami. This synoptic approach to simulating coseismic and postseismic deformational systems may significantly advance tectonic and tsunami coastal hazard assessment capabilities for the SAE and impact future assessments of similar mega-thrust earthquakes for other subduction zones hosting high population densities, such as the upper US West Coast (Cascadia) and Japan. Techniques for designing and implementing FEMs will be disseminated to the scientific community during a workshop in the latter stages of this project. Students will use Abaqus software to construct FEMs that simulate fault-slip, which can be used in forward and inverse models of deformation and drive of postseismic processes, including poroelastic and viscoelastic deformation.

2004年12月26日M9.2苏门答腊 - 安达曼地震（SAE）是有史以来第三大地震，破裂的边界破裂了边界，将俯冲的印度 - 澳大利亚板块与超大的缅甸板块分开，并引发了毁灭性的海啸，对9个与印度海洋接壤的国家产生了重大影响。在震中附近，海啸在苏门答腊北部的某些沿海地区造成了超过30米的升级，几乎立即杀死了200,000多人。 SAE的破裂包括超过20米的断层滑移，基于相关的地震数据和海底和地面变形的GPS测量。这种变形的幅度为进行区域尺度的原位流变学实验提供了罕见的机会，其中coseissic断裂滑移是冲动，随后的变形是响应。对这些测得的扰动进行建模可以测试Coseismic的假设（包括海啸生成）和后视见性（包括地震耦合和海啸奔波）的行为。具体而言，俯冲带的有限元模型（FEM）靠近震中附近，可以定量评估流变方法分配和过程，对控制coseismiss和后视性行为的压力，应变和孔隙压力的作用。然后，海啸繁殖模型可以使用女性生成的海底变形来预测沿海的升级。 SAE的这项建模和解释性研究将解决以下科学问题：（1）材料特性的分布（即俯冲带中岩石地层的结构，密度，孔隙和刚度）如何影响断层滑移估计？ （2）这种分布如何影响海底变形，海啸起源和加速预测？ （3）毛弹性和粘弹性后变形的时间和分布是什么？ （4）需要什么何时？ （5）库仑应力和孔隙压力瞬变是否与余震发生相关？这些问题的基础是一个更基本的问题：我们如何构建和约束coseismisic和seasissic行为的模型作为过程的综合，所有这些都会有助于变形系统？因此，拟议的研究的主要目标是确定描述SAE的Coseissic和后视见性行为的流变特性的分布和校准。更具体地说，FEM模拟将解决空间和时间上的余震发生（包括SAE与2005年3月25日M8.7 Nias地震之间发生的应力耦合，距离SAE Epicenter 350公里）。女性生成的海底变形预测将驱动海啸传播模拟。因为我们预计材料特性（以及可能的二次散布断层）的变化将导致长时间和较短的海底变形，因此将使用分散长波模型Funwave进行海啸和传播模拟。海啸危害将以印度洋受影响最大的地区（例如苏门答腊北部）的模拟加速和淹没来表达，并与观察到的12/26/04 Tsunami的影响相比。这种模拟Coseismisic和后震后变形系统的概要方法可能会显着提高SAE的构造和海外沿海危险评估能力，并影响对其他高俯冲钻孔类似的巨型大众地震的未来评估。在该项目后期的研讨会期间，设计和实施FEM的技术将被传播到科学界。学生将使用ABAQUS软件来构建模拟断层滑移的FEM，这些FEM可用于变形和逆向驱动器的后震动过程，包括毛弹性和粘弹性变形。