The Physics of the Earthquake Source and Radiated Waves: Frequency Dependence, Spatial Distribution, and Directivity in Elastodynamic Models of Repeated Fault Ruptures

该建议探讨了一类新的弹性动力学模型的扩展，这类模型已经成功地模拟了广泛的地震行为，以研究地震过程中产生的辐射能量。 由于辐射能量是观测数据的最丰富来源，它最终将为地震模型提供最重要的约束。 以前的工作已经研究了如何总辐射能量可以敏感的震源物理，表现出不同的滑动弱化与速度弱化摩擦的弹性动力断层模型。 该项目建议更深入地研究辐射能量场，以寻找源物理学的进一步特征。 首先，该项目将研究远场辐射能量的频谱内容，而不是只关注总辐射能量，将其作为力矩的函数进行检查，并针对一系列摩擦。 在这里，我们可以看到滑动与速度削弱摩擦的进一步差异。 接下来，研究将检查辐射的空间依赖性，研究辐射能量如何随着从远场移动到近场而变化。 在这里，该项目将检查相对于事件震源的固定半径和角度的平均谱能量密度，对类似大小的事件进行平均。 有趣的距离依赖性的影响，特别是对于地壳深度的距离。 最后，研究将寻找断层运动与辐射能量场方面的相关性。 具体而言，模型显示滑动和传播速度的变化，通过应力不均匀性的断层上的滑动脉冲，这些变化是如何表现在方向性的影响和频谱内容？

This proposal examines the extension of a new class of elastodynamic models, which have already been successful at simulating a wide range of earthquake behaviors, to the study of the radiated energy produced during earthquakes. Because radiated energy is the richest source of observational data, it will ultimately provide the most significant constraints on earthquake models. Previous work has examined how total radiated energy can be sensitive to the earthquake source physics, showing differences for slip weakening versus velocity weakening friction in elastodynamic fault models. This project proposes to look deeper into the radiated energy field to look for further signatures of the source physics. First, rather than looking only at the total radiated energy, the project will investigate the spectral content of the far field radiated energy, examining this as a function of moment, and for a range of frictions. Here we can expect to see further differences for slip versus velocity weakening friction. Next the research will examine the spatial dependence of the radiation, looking at how the radiated energy changes as one moves from the far field to the near field. Here, the project will examine the average spectral energy density for a fixed radius and angle relative to the event hypocenter, averaging over events of similar size. Interesting distance dependence effects are expected, particularly for distances of order a crustal depth away. Finally, the research will look for correlations in the motions on the fault with aspects of the radiated energy field. Specifically, the models show slip and propagation velocity variations as slip pulses pass through stress heterogeneities on the fault; how are these variations manifested in directivity effects and spectral content?