Towards a Comprehensive Understanding of Episodic Tremor and Slip

在这项研究中，我们开发和应用技术来提高我们对最近发现的一种现象的理解，这种现象被称为深部非火山地震。深震是一种或多或少持续但微弱的地面震动，与大地震但非常缓慢的地震有关。地震的性质是长时间但不是脉冲的地面运动，这需要地震学家采用新的和创新的方法，因为适用于普通地震的常规分析不能适用于地震。我们目前正在改进PI和他的同事们已经开发的方法，并将它们应用于不同地区的震颤。我们还在继续开发新的和改进的震颤分析方法。其中包括低频地震的匹配过滤分析，用于检测低频地震的震动幕的连续自相关分析，以及用于识别相似但不相同的小规模低频地震的“子空间”检测算法。我们使用从这一分析中产生的理解来解决震颤行为的系统性，以及震颤过程的力学。拟议研究的地区都是地震发生有很好记录的地区，特别是：卡斯卡迪亚、日本西南部和加利福尼亚州中部。地震的战略位置--我们预计未来大地震将在锁定带的边界启动--以及对它代表板块边界剪切滑动的新认识，使其成为一个重要的研究目标，对地震预报具有重要的潜在意义。特别是，更好的理解应该有助于科学家评估深震对卡斯卡迪亚俯冲带和加利福尼亚州中部地震危险的重要性，在那里，地震在圣安德烈亚斯断层的乔拉姆段深处观察到，这段断层已经150多年没有破裂了。另一个更广泛的重要影响是这项工作的国际色彩：美国研究人员和研究生将与东京大学、国家地球科学和灾害预防研究所以及日本其他机构的研究人员在这项研究的大部分内容上进行合作。

In this research we develop and apply techniques to improve our understanding of a recently discovered phenomenon known as deep, non-volcanic tremor. Deep tremor is a more or less incessant, but weak, shaking of the ground that has been associated with large, but very slow earthquakes. The nature of tremor, with long, but not impulsive, episodes of ground motion requires new and innovative approaches from seismologists because the usual analysis applied to ordinary earthquakes cannot be applied to tremor. We are currently improving methods that have already been developed by the PI and his colleagues, and applying them to tremor in different areas. We are also continue to develop new and improved methods for tremor analysis. Among these are matched-filter analysis of low frequency earthquakes, a running auto-correlation analysis of tremor episodes to detect low frequency earthquakes, and a ''sub-space'' detection algorithm for identifying similar, but not identical small low frequency earthquakes. We use the understanding that emerges from this analysis to address the systematics of tremor behavior of the mechanics of the tremor process. The areas of the proposed study are all areas where tremor occurrence is well documented, specifically: Cascadia, Southwest Japan, and Central California. The strategic location of tremor -- at the boundary of the locked zone where we expect future large earthquakes to initiate -- and the emerging understanding that it represents shear slip on the plate boundary, makes this an important research target with significant potential implications for earthquake forecasting. In particular, an improved understanding should help scientists to assess the significance of deep tremor for earthquake hazard in the Cascadia subduction zone and in central California, where tremor is observed deep under the Cholame segment of the San Andreas Fault, a segment that has not ruptured in over 150 years. Another important broader impact is the international flavor of this work: U.S. researchers and graduate students will collaborate with researchers at the University of Tokyo, the National Institute for Earth Sciences and Disaster Prevention, and other institutions in Japan on significant portions of this research.