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。 与几十年来已知的几秒钟内发生的常规地震断层滑动或稳定变形不同，大部分深断层在几天或几周内不稳定地移动，然后停止移动数月至数年，然后再次缓慢移动。这种新的模式，零星耦合变形和弱地震辐射被称为幕式震颤和滑动（ETS）在几个俯冲带都有发现它从卡斯卡迪亚大型逆冲断层的锁定部分每14个月周期性地向下倾斜。ETS区与俯冲带的锁定和危险部分的密切关系和可能的相互作用要求更好地理解ETS现象。阵列阵列项目是对ETS周围许多关键问题的全面研究，利用临时地震部署，以前所未有的细节来成像卡斯卡迪亚俯冲带震颤。具体而言，一组阵列被部署在奥林匹克半岛，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，六个20站阵列，和一行站连接两个阵列。 还有一套由15个短周期和7个宽带连续记录地震仪组成的骨干设备，这些地震仪阵列揭示了地震位置和深度、迁移、高频频谱内容的时空细节，以及更好的地震分辨率和低频震源特征。 对来自这个独特阵列的数据进行分析将回答有关震颤的许多关键问题，并进一步阐明ETS过程的物理学，并为卡斯卡迪亚地震减灾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.