A Global Survey of the Initiation of Large Earthquakes: The Influence of Earthquake Magnitude and Depth on the Rate of Growth of Moment Release

全球大地震发生调查：地震震级和深度对力矩释放增长率的影响

• 批准号: 0106680
• 负责人: Heidi Houston
• 金额: $ 10.29万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-07-15 至 2005-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0106680&HistoricalAwards=false
• 关键词: Global; Survey; Initiation; Large; Earthquakes

Abstract for proposal EAR 0106680 (PH # 63x)Title: A global survey of the initiation of large earthquakes: The influence of earthquake magnitude and depth on the rate of growth of moment releasePI: Heidi Houston, University of California, Los AngelesHow earthquakes initiate is a key issue in understanding the process of seismic rupture. For example, the question of how seismic ruptures grow and whether large earthquakes initiate in a different manner than small ones has attracted significant attention in recent years, but remains controversial. We propose to determine the initial rates of growth of earthquake ruptures (initial source time functions) with detailed resolution in time for many (~150) large earthquakes (with depths of 15 to 100 km and MW \204 6.7) directly from seismograms. Systematic comparison and statistical analysis of the results will enable us to determine the influences of factors such as earthquake magnitude, source depth, focal mechanism, and tectonic setting on how ruptures grow in their first few seconds. Several recent results suggest that such influences may exist. A slow beginning to rupture (seismic nucleation phase) proportional in duration to the final magnitude and lasting 4 to 10 seconds for MW 8.0 to 8.2 earthquakes has been put forward as a general feature. The work proposed here should detect its systematic presence or absence in our magnitude range. Systematic differences in the energy budgets of small earthquakes compared to large ones have been proposed, which suggest that melting or fluid pressurization occurs during large but not small events, and affects dynamic rupture. The duration of rupture is known to decrease with depth, implying an increase in the rate of initial rupture growth. Finally, rupture growth could be affected by the aspect ratio (shape) of the fault, which is closely related to tectonic regime. Differences (or their absence) in rate of initiation with magnitude, depth, or other parameters can place constraints on the physical processes acting during rupture initiation.

摘要提案编号0106680（PH #63 x）标题：大地震启动的全球调查：地震震级和深度对矩释放增长率的影响PI：海蒂休斯顿，加州大学，洛杉矶地震如何启动是理解地震破裂过程的关键问题。 例如，地震破裂如何增长以及大地震是否以与小地震不同的方式引发的问题近年来引起了人们的极大关注，但仍然存在争议。我们建议直接从地震记录中确定许多（~150）大地震（深度为15至100 km，MW为6.7）的地震破裂增长的初始速率（初始震源时间函数）。 对这些结果进行系统的比较和统计分析，将使我们能够确定地震震级、震源深度、震源机制和构造背景等因素对破裂在最初几秒钟内如何发展的影响。 最近的一些结果表明，这种影响可能存在。 一个缓慢的开始破裂（地震成核阶段）的持续时间成比例的最终震级和持续4至10秒的MW 8.0至8.2地震已被提出作为一个一般特征。 这里提出的工作应该检测它在我们的量级范围内的系统存在或不存在。小地震的能量收支与大地震相比存在系统性差异，这表明在大地震而不是小地震期间发生了熔融或流体加压，并影响了动态破裂。 破裂的持续时间是众所周知的，随着深度的减少，这意味着在初始破裂增长率的增加。 最后，破裂的增长可能会受到影响的纵横比（形状）的断层，这是密切相关的构造体制。 不同（或不存在）的幅度，深度，或其他参数的启动速率可以放置在破裂启动过程中的物理过程的约束。