Unlocking the Inner Life of Cascadia Tremor with an Array of Arrays

在过去的10年里，人们观察到了一种奇怪的断层滑动方式。与几十年来已知的常规地震断层在几秒钟内滑动或稳定变形不同，深断裂的大部分在几天或几周内不稳定地移动，然后停止运动几个月到几年，然后再次以慢动作蹒跚前进。这种零星耦合变形和弱地震辐射的新模式被称为幕式震颤和滑动(ETS)，已在几个俯冲带被发现。大约每14个月，它就会从卡斯卡迪亚巨型逆冲带的锁定部分周期性地向下倾斜。ETS带与俯冲带的锁定和危险部分之间的密切关系和可能的相互作用要求更好地了解ETS现象。阵列阵列项目是对围绕ETS的许多关键问题的综合研究，该项目利用临时地震部署，旨在以前所未有的细节拍摄卡斯卡迪亚俯冲带地震。具体地说，在奥林匹克半岛上部署了一组阵列，以记录2009年夏季和2010年秋季发生的ETS事件，包括一个40站阵列，6个20站阵列，以及连接其中两个阵列的一系列站。此外，还有一套由15台短周期和7台宽带连续记录地震仪组成的主干设备。该阵列揭示了地震位置和深度的时空细节、地震的迁移、高频的频谱含量以及更好的地震和低频震源特征的分辨率。对这一独特阵列的数据分析将回答许多有关地震的关键问题，并进一步阐明ETS过程的物理机制，并为缓解卡斯卡迪亚地震灾害的棘手问题提供答案。

In the last 10 years, a strange way for faults to slip has been observed. Rather than regular earthquake fault slip in a matter of seconds or steady deformation, both of which have been known to occur for decades, large parts of deep faults move unsteadily over the course of days or weeks, then stop moving for months to years before lurching in slow motion again.This new mode of sporadic coupled deformation and weak seismic radiation is termed Episodic Tremor and Slip (ETS) has been discovered in several subduction zones. It recurs episodically down-dip from the locked portion of the Cascadia megathrust about every 14 months. The close relationship and likely interaction of the ETS zone with the locked and hazardous portions of subduction zones mandate better understanding of the ETS phenomena.The Array of Arrays project is a comprehensive study of many of the key questions surrounding ETS utilizing a temporary seismic deployment designed to image Cascadia Subduction Zone tremor in unprecedented detail. Specifically, a set of arrays are being deployed on the Olympic Peninsula to record the ETS events occurring during Summer 2009 and Fall 2010, comprising one 40-station array, six 20-station arrays, and a line of stations connecting two of the arrays. There is also a backbone set of 15 short-period and 7 broadband continuously recording seismometers.The Array of arrays is unveiling the spatio-temporal details of the tremor location and depth, its migration, its spectral content at high frequencies, as well as better resolution of tremor and low-frequency earthquake source character. Analysis of the data from this unique array will answer many key questions about tremor and further elucidate the physics of the ETS process, and provide answers to vexing issues of Cascadian earthquake hazard mitigation.