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

提案摘要0106680(PH#63x)标题：大地震起源的全球调查：地震震级和深度对力矩释放增长率的影响PI：加州大学洛杉矶分校的Heidi Houston地震如何引发是理解地震破裂过程的关键问题。例如，地震破裂如何发展以及大地震是否以不同于小地震的方式引发的问题近年来引起了人们的极大关注，但仍存在争议。我们建议直接从地震记录中确定许多(~150)大地震(深度15~100公里，Mw\2046.7)的地震破裂的初始速率(初始震源时间函数)，并在时间上有详细的分辨率。结果的系统比较和统计分析将使我们能够确定地震震级、震源深度、震源机制和构造环境等因素对破裂在最初几秒钟内如何增长的影响。最近的几个结果表明，这种影响可能是存在的。对于MW8.0~8.2级地震，一般存在一个持续时间与最终震级成正比的缓慢开始破裂(地震成核期)，持续时间为4~10秒。这里提出的工作应该在我们的震级范围内检测到它的系统存在或不存在。与大地震相比，小地震能量收支存在系统性差异，这表明熔融或流体增压作用发生在大地震而不是小地震期间，并影响动态破裂。破裂的持续时间随着深度的增加而减少，这意味着初始破裂生长的速度增加。断裂发育受断层长宽比(形状)的影响，与构造体制密切相关。起裂速率与震级、深度或其他参数的不同(或不存在)可能会对破裂起爆过程中的物理过程施加限制。

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.