During the last two decades, space geodesy allowed mapping accurately rupture areas, slip distribution, and seismic coupling by obtaining refined inversion models and greatly improving the study of great megathrust earthquakes. A better understanding of these phenomena involving large areas of hundreds of square kilometers came from the last gravity satellite mission that allowed detecting mass transfer through the Earth interior. In this work, we performed direct modeling of satellite GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) derived gravity gradients up to degree/order N = 200 of the harmonic expansion and then corrected this by the effect of topography. Cutting off the model up to this degree/order allows inferring mass heterogeneities located at an approximate depth of 31 km, just along the plate interface where most (but not all) significant slip occurs. Then, we compared the vertical gravity gradient to well-constrained coseismic slip models for three of the last major earthquakes along the Sunda interface. We analyzed seismic rupture behavior for recent and for historical earthquakes along this subduction margin and the relationship of the degree of interseismic coupling using the gravity signal. From this, we found that strong slip patches occurred along minima gravity gradient lobes and that the maximum vertical displacements were related quantitatively to the gravity-derived signal. The degree of interseismic coupling also presents a good correspondence to the vertical gravity gradient, showing an inverse relationship, with low degrees of coupling over regions of relatively higher density. This along-strike segmentation of the gravity signal agrees with the along-strike seismic segmentation observed from recent and historical earthquakes. The thermally controlled down-dip ending of the locked fault zone along central Sumatra also presented an inverse relationship with the density structure along the forearc inferred using our modeling. From this work, we inferred different mass heterogeneities related to persistent tectonic features along the megathrust and along the marine forearc, which may control strain accumulation and release along the megathrust. Combining these data with geodetical and seismological data could possibly delimit and monitor areas with a higher potential seismic hazard around the world.

在过去的二十年中，通过获取精细的反演模型并极大地改善了大推力地震的研究，通过空间大地测量可以准确绘制破裂区域，滑动分布和地震耦合图。上一次重力卫星飞行任务使人们能够更好地了解涉及数百平方公里大面积区域的这些现象，该任务使我们能够检测到通过地球内部的质量转移。在这项工作中，我们对卫星GOCE（重力场和稳态海洋环流探测器）导出的重力梯度进行了直接建模，直至高达谐波的度数/阶数N = 200，然后通过地形效应对其进行了校正。将模型切割到这个程度/级别可以推断出大约31 km深度处的质量异质性，刚好沿着大部分（但不是全部）明显滑动发生的板界面。然后，我们将沿Sunda界面发生的最近三场主要地震的垂直重力梯度与约束良好的同震滑动模型进行了比较。我们利用重力信号分析了沿该俯冲幅度的近期和历史地震的地震破裂行为，以及地震耦合程度之间的关系。由此，我们发现沿着最小重力梯度波瓣出现了强烈的滑动斑块，并且最大垂直位移与重力衍生信号定量相关。地震耦合程度也与垂直重力梯度表现出良好的对应关系，显示出反比关系，在相对较高密度的区域上耦合程度较低。重力信号的这种沿震的分段与从最近和历史地震中观察到的沿震的地震分段是一致的。利用我们的模型推断，沿苏门答腊中部锁定断层带的热控制下倾端也与沿前臂的密度结构呈反比关系。通过这项工作，我们推断出与沿大推力和海洋前臂的持久构造特征有关的不同质量异质性，这可能控制沿大推力的应变积累和释放。将这些数据与大地测量和地震数据相结合，可能会划定并监视世界范围内潜在地震危险性更高的区域。