Modelling earthquakes and earth,s interior based upon exascale simulations of seismic wave propagation

我们建议使用现代数值方法和计算机，以改善地震和地球内部的地震波传播的正向和反向模拟的基础上的图像。模拟的基础上的频谱元素的方法和帐户的不均匀性，在地壳和地幔，地形，各向异性，衰减，流体-固体的相互作用，自引力，旋转和海洋。在未来的艾级机器上，我们将能够在全球模拟中达到远低于1 Hz的频率。我们的目标是超越经典的走时层析成像，并使用包含在整个地震波形的信息。通过绘制地震层析成像、气候和海洋动力学中流行的伴随方法以及时间反演成像之间的联系，我们已经证明，层析成像反演中的一次迭代可以基于针对每次地震的两次数值模拟来执行：一次计算针对当前模型，第二次伴随计算使用接收器处的时间反演信号作为同时的虚拟源。这最终打开了解决3D逆问题的大门，即使用数据和数据之间的剩余差异的问题。

We propose to use modern numerical methods and computers to improve images of earthquakes and Earth's interior based upon forward and inverse simulations of seismic wave propagation. The simulations are based upon a spectral-element method and account for heterogeneity in the crust and mantle, topography, anisotropy, attenuation, fluid-solid interactions, self-gravitation, rotation, and the oceans. On future exascale machines we will able to reach frequencies well below 1 Hz in global simulations. Our objective is to go beyond classical traveltime tomography, and to use information contained in entire seismic waveforms. By drawing connections between seismic tomography, adjoint methods popular in climate and ocean dynamics, and time-reversal imaging, we have demonstrated that one iteration in tomographic inversions may be performed based upon just two numerical simulations for each earthquake: one calculation for the current model and a second adjoint calculation that uses time-reversed signals at the receivers as simultaneous, fictitious sources. This has finally opened the door to solving the 3D inverse problem, namely the problem of using the remaining differences between the data and the