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Months-longthousand-kilometre-scale wobbling before great subduction earthquakes

机译：大俯冲地震前数月千公里规模的摆动

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Observed reversals in GNSS surface motions suggests greatly enhanced slab pull in the months preceding the great subduction earthquakes in Maule (Chile, 2010) and Tohoku-oki (Japan, 2011) of moment magnitudes 8.8 and 9.0.Megathrust earthquakes are responsible for some of the most devastating natural disasters(1). To better understand the physical mechanisms of earthquake generation, subduction zones worldwide are continuously monitored with geophysical instrumentation. One key strategy is to install stations that record signals from Global Navigation Satellite Systems(2,3) (GNSS), enabling us to track the non-steady surface motion of the subducting and overriding plates before, during and after the largest events(4-6). Here we use a recently developed trajectory modelling approach(7) that is designed to isolate secular tectonic motions from the daily GNSS time series to show that the 2010 Maule, Chile (moment magnitude 8.8) and 2011 Tohoku-oki, Japan (moment magnitude 9.0) earthquakes were preceded by reversals of 4-8 millimetres in surface displacement that lasted several months and spanned thousands of kilometres. Modelling of the surface displacement reversal that occurred before the Tohoku-oki earthquake suggests an initial slow slip followed by a sudden pulldown of the Philippine Sea slab so rapid that it caused a viscoelastic rebound across the whole of Japan. Therefore, to understand better when large earthquakes are imminent, we must consider not only the evolution of plate interface frictional processes but also the dynamic boundary conditions from deeper subduction processes, such as sudden densification of metastable slab.
机译：观测到的GNSS表面运动的逆转表明，在矩量级为8.8和9.0的Maule（智利，2010）和Tohoku-oki（日本，2011）发生大俯冲地震之前的几个月中，平板拉力大大增强了。最破坏性的自然灾害（1）。为了更好地了解地震发生的物理机制，全球范围内的俯冲带都用地球物理仪器进行了连续监测。一种关键策略是安装可记录来自全球导航卫星系统（2,3）（GNSS）的信号的台站，使我们能够在最大事件发生之前，之中和之后跟踪俯冲和俯冲板块的非稳定表面运动（4）。 -6）。在这里，我们使用最近开发的轨迹建模方法（7），该方法旨在从每日GNSS时间序列中分离出长期的构造运动，以显示2010年智利的Maule（矩量级8.8）和2011年的Tohoku-oki，日本的矩量9.0 ）地震发生之前，地表位移逆转了4-8毫米，持续了几个月，跨越了数千公里。东北冲地震前发生的地表位移逆转的模型表明，最初缓慢的滑动，随后菲律宾海平板突然突然下滑，速度如此之快，以至于引起了整个日本的粘弹性反弹。因此，为了更好地了解即将发生大地震的情况，我们不仅要考虑板界面摩擦过程的演变，而且还要考虑更深的俯冲过程的动态边界条件，例如亚稳平板的突然致密化。

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    《Nature》 |2020年第7805期|628-635|共8页
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    Helmholtz Ctr Potsdam GFZ German Res Ctr Geosci Potsdam Germany;

    Univ Concepcion Dept Geofis Concepcion Chile;

    Helmholtz Ctr Potsdam GFZ German Res Ctr Geosci Potsdam Germany|Free Univ Berlin Inst Geol Sci Berlin Germany;

    Free Univ Berlin Inst Geol Sci Berlin Germany;

    Univ Chile Natl Seismol Ctr Santiago Chile;

    Ohio State Univ Sch Earth Sci Columbus OH 43210 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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