EAGER: Upper-plate Response to a Great Eathquake: Integrating Deformation from Seismic to Geologic Timescales

正如2011年日本东北部Mw9.0地震和海啸所清楚表明的那样，发生在沿着俯冲带板块边界的地震可能是地球上最大和最具破坏性的自然事件之一。预测俯冲带的哪些区域最容易受到这些大型逆冲事件的影响的一个关键是估计在大地震之前积累的未释放的板块运动的幅度和位置。目前的俯冲带模型假设在俯冲界面上方的上板块上观察到的变形与板块界面上的滑移缺陷之间存在相对简单的联系;然而，越来越清楚的是，板块界面上同震滑移的实际分布以及由此产生的上板块响应要复杂得多。为了绘制未释放的地震矩的积累图，有必要更好地了解如何将地震前、地震时和地震后的变形观测（在远离板块界面的陆地上进行）与板块边界断层本身的滑动积累和释放的实际过程相对应。该项目将利用观测到的地壳变形（全球定位系统、地质测绘、地震活动性）的非常丰富的数据集，这些数据集的观测时间范围从地质（数百万年）到地震周期（数百至数千年）到东北地震事件附近的地震破裂（分钟至秒）不等。结合地质时间尺度和地震周期时间尺度观测，可以改进俯冲带应变演化的概念模型。 通过更好地了解俯冲带中的上板块如何充当变形过滤器，使用上板块变形的观测结果，研究小组将能够大大改进对板块边界滑动缺陷的估计，（其可以响应于主地震而被地震激活），该项目试图弥补当前俯冲科学中的一个重大空白--地质时间尺度上的构造观测与当前地球物理/地球物理观测之间的差距。通过地震周期对形变进行大地测量观测。这项研究的结果将推动俯冲科学更好地估计地震潜力，可以预期的最大震级，并改进对大地震期间最大能量（力矩）释放位置的估计-所有这些都是减少人类对主要俯冲带地震灾害脆弱性的关键组成部分。

As was clearly demonstrated in the 2011 Mw 9.0 Tohoku (Japan) earthquake and tsunami, earthquakes that occur along subduction zone plate boundaries can be both among the largest and most devastating natural events on Earth. One key to anticipating what regions of subduction zones are most vulnerable to these mega-thrust events is to estimate the magnitude and location of un-released plate motion that accumulates prior to a major earthquake. Current subduction zone models assume a relatively simple link between observed deformation on the upper plate above the subduction interface and this slip deficit on the plate interface; however it is becoming clear that the actual distribution of co-seismic slip on the plate interface and the resulting upper plate response is substantially more complex. In order to map the accumulation of unreleased seismic moment, it is necessary to better understand how to map the observations of pre-, co- and post-earthquake deformation (made on land away from the plate interface) to the actual processes of slip accumulation and release on the plate boundary fault itself. This project will utilize a very rich data set of observed crustal deformation (GPS, geologic mapping, seismicity), observed on time scales ranging from geologic (millions of years) to earthquake cycle (hundreds-to-thousands of years) to earthquake rupture (minutes-to-seconds) in the vicinity of the Tohoku event. By combining geologic time-scale and seismic cycle time-scale observations conceptual models of subduction zone strain evolution can be improved. With a better understanding of how the upper plate in a subduction zone acts as a deformational filter, using observations of upper plate deformation the research team will be able to develop substantially improved estimates of plate boundary slip deficits, post-seismic loading of active structures on the upper plate (which may becomes seismically activated in response the main earthquake), and a better sense of seismic potential of subduction boundaries.This project is an attempt to bridge a substantial gap in current subduction science - the gap between tectonic observations on geologic time-scales and current geophysical/geodetic observations of deformation through the earthquake cycle. Outcomes from this research will move subduction science toward better informed estimates of earthquake potential, maximum magnitudes that could be expected, and improved estimates of locations of maximum energy (moment) release during major earthquakes - all key components in reducing human vulnerability to major subduction zone earthquake hazards.