Developments in the physical modelling of the Earth’s interior and space geodesy make it possible nowadays to exploit the gravity signature and deformation patterns, including their time variations, caused by megathrust earthquakes at subduction zones with moment magnitude M_w higher than 9.0, as the 2004 Sumatran and 2011 Tohoku-Oki ones. In order to achieve these goals, it has been necessary to develop realistic self-gravitating, compressible Earth’s models, stratified in terms of density and rheological properties of the Earth’s interior. This new class of models allows us to comprehend some not yet fully appreciated mathematical aspects of viscous stress relaxation, such as the interplay between discrete and continuous relaxation spectra depending on the style of density stratification of the viscoelastic mantle or the effects on the gravity fields of sometimes used simplified treatments of compressibility. We show how GRACE and GOCE data allow us to invert for the mass redistribution, inner volume variations, gravity perturbations and surface deformation affecting areas and volumes larger than those embedding the gouge of the earthquakes, including the slip distribution over the fault surface. A correct interpretation of the mass redistribution process for megathrust earthquakes is important for the understanding of the physics of the ocean and Solid Earth coupling, causing the tsunami which struck Sumatra and Thailand and the eastern coast of Japan due to the huge amount of water washed out from the epicentral region as seen from GRACE data and physical modelling. In the present study we focus on the physics of the co-seismic and post-seismic gravity changes due to a M_w = 7.0 scenario normal-fault earthquake, comparable to the 1980 Irpinia earthquake. Our modelling provides the earthquake gravity effects within the perspective of the upcoming Next Generation Gravity Missions (NGGM), designed to detect the gravity anomalies caused by earthquake magnitudes as low as M_w = 7 as well as the gravity anomalies due to the active tectonic processes responsible for the earthquakes. It is expected that the time-dependent gravity will be exploited at the GOCE spatial resolution and at GRACE time resolution, or even better, thanks to a new class of payload instrumentation, based on a laser ranging system measuring the distance variation between one or two pairs of satellites flying in formation at altitudes of about 300 km and at about 100 km separation, each satellite differently affected by the gravity changes of our Planet.

中文翻译：

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来自太空引力任务的地震物理学

地球内部和空间大地测量的物理建模的发展使得如今有可能利用重力特征和变形模式，包括它们的时间变化，这些变化是由矩量级为M _w的俯冲带的特大推力地震引起的。高于9.0，例如2004年的苏门答腊和2011年的东北冲绳。为了实现这些目标，有必要开发现实的自重，可压缩的地球模型，并根据地球内部的密度和流变特性对其进行分层。这类新模型使我们能够理解粘性应力松弛的一些尚未完全理解的数学方面，例如离散和连续松弛谱之间的相互作用，这取决于粘弹性地幔的密度分层样式或对重力场的影响。有时使用简化的可压缩性处理。我们展示了GRACE和GOCE数据如何使我们反演质量再分布，内部体积变化，重力扰动和地表变形影响的面积和体积要大于埋入地震凿孔的面积和体积，包括断层表面的滑动分布。正确解释大推力地震的质量重新分配过程，对于理解海洋和固体地球耦合的物理特性非常重要，因为冲走了大量水，导致了海啸袭击了苏门答腊，泰国和日本的东海岸。从GRACE数据和物理建模中可以看到震中区域。在本研究中，我们重点关注由于地震引起的同震和震后重力变化的物理学。正确解释大推力地震的质量重新分配过程，对于理解海洋与固体地球耦合的物理特性非常重要，由于大量水被冲走，导致海啸袭击了苏门答腊，泰国和日本的东海岸。从GRACE数据和物理建模中可以看到震中区域。在本研究中，我们重点关注由于地震引起的同震和震后重力变化的物理学。正确解释大推力地震的质量重新分配过程，对于理解海洋与固体地球耦合的物理特性非常重要，由于大量水被冲走，导致海啸袭击了苏门答腊，泰国和日本的东海岸。从GRACE数据和物理建模中可以看到震中区域。在本研究中，我们重点关注由于地震引起的同震和震后重力变化的物理学。M _w = 7.0情景正常断层地震，与1980年Irpinia地震相当。我们的模型在即将到来的下一代重力任务（NGGM）的角度内提供了地震重力效应，旨在检测低至M _w =的地震烈度引起的重力异常。以及由于地震活动的构造过程引起的重力异常。预计将借助GOCE空间分辨率和GRACE时间分辨率，甚至更好的时间依赖重力，这要归功于新型的有效载荷仪器，该仪器基于测量一两个物体之间距离变化的激光测距系统成对的卫星以大约300公里的高空飞行，并且间隔约100公里，每颗卫星受地球引力变化的影响不同。