Radiation of Teleseismic Body Waves from Dynamic Faults

动力断层远震体波的辐射

• 批准号: 0208494
• 负责人: Thomas Heaton
• 金额: $ 5.75万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-15 至 2003-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0208494&HistoricalAwards=false
• 关键词: Radiation; Teleseismic; Body; Waves; Dynamic

Thomas H. HeatonEAR-0208494This project is examining the effects of fault opacity (the tendency of reflected phases to be trapped in the hanging wall of the fault) on radiated energy by constructing models of P and SH body waves from shallow thrust fault earthquakes at teleseismic distances. Three-dimensional finite-element models are used to calculate rupture history assuming a variety of friction models. These slip histories are used to calculate the teleseismic body waves that results from the different friction models. Systematic differences are determined between these dynamic models and traditional dislocation models that are commonly used for determining seismic moments. The main goal is to quantify how teleseismic P and SH body waves from dipping faults are affected by near-source interactions between the seismic waves and a dynamically slipping fault. It has been common practice to estimate seismic moments by modeling these teleseismic waveforms using double-couple source representations. In these models, the medium is modeled as an elastic continuum with displacement jumps caused by distributions of double-couple body forces. While these models satisfy all boundary conditions within a continuous medium, they are not necessarily compatible with the frictional stress boundary conditions on the slipping fault (a discontinuous medium). In particular, shear waves that reflect off of the Earth's surface are generally allowed to propagate back through the slipping fault without reflection; this is sometimes referred to as a transparent fault. There is a long-standing question about whether or not systematic errors in determining earthquake sizes have been introduced by using transparent fault models. This study should provide quantitative estimates of the importance of this effect.

Thomas H. HeatonEAR-0208494该项目正在通过构建远震距离浅逆冲断层地震的 P 和 SH 体波模型来研究断层不透明度（反射相被困在断层上盘中的趋势）对辐射能量的影响。三维有限元模型用于计算假设各种摩擦模型的破裂历史。这些滑动历史用于计算由不同摩擦模型产生的远震体波。这些动态模型与通常用于确定地震矩的传统位错模型之间存在系统差异。 主要目标是量化来自倾斜断层的远震 P 和 SH 体波如何受到地震波和动态滑动断层之间的近源相互作用的影响。通过使用双耦合源表示对这些远震波形进行建模来估计地震矩是常见的做法。在这些模型中，介质被建模为弹性连续体，其位移跳跃是由双力偶体力的分布引起的。虽然这些模型满足连续介质内的所有边界条件，但它们不一定与滑断层（不连续介质）上的摩擦应力边界条件兼容。特别是，从地球表面反射的剪切波通常可以通过滑动断层传播回来，而不会发生反射；这有时被称为透明故障。一个长期存在的问题是，使用透明断层模型是否会引入确定地震震级的系统误差。这项研究应该提供这种效应重要性的定量估计。