Broadband Seismological Investigations of Earth Structure and Earthquake Sources

这是一个为期四年的项目，目的是对地球深部结构和震源进行地震学调查，利用现代数字地震波形数据，解决有关地幔动力结构和大地震破裂过程的基本问题。板间地震破裂持续时间的系统性变化的发现将通过对俯冲带中巨型逆冲断层上的极小逆冲地震的震源有限性的详细分析来跟进。平均而言，这些浅层事件被发现需要2至3倍的时间比可比的地震矩事件在更大的深度破裂。确定这是否是由于低应力降或低破裂速度，需要确定破裂尺寸，这将采用理论和经验绿色函数的方向性分析。还将对主要的边界层动力学进行研究。中深源地震S波的振幅和到达时间异常将通过三维方法模拟，以帮助约束速度结构和深板下延的命运。将使用波形叠加方法，检测和表征俯冲板周围的地幔中的速度和阻抗对比的影响，这些downpermons在地幔中的相平衡进行检查。将使用新的数字数据集和UCSC最近开发的混合2D/3D波传播方法分析核幔边界附近的复杂速度不均匀性。

This is a four-year project to conduct seismological investigations of deep earth structure and earthquake sources.Using modern digital seismic waveform data, fundamental questions about dynamical structures in the mantle and rupture processes of large earthquakes will be addressed. The discovery of systematic variation of interplate earthquake rupture duration will be followed-up by detailed analysis of the source finiteness for very small thrust earthquakes on the megathrust fault in subduction zones. On average, these shallow events are found to take 2 to 3 times longer to rupture than comparable seismic moment events at larger depths. Establishing whether this is due to low stress drop or low rupture velocity requires determination of rupture dimensions, which will be pursued using directivity analysis with theoretical and empirical Green's functions. Studies of major boundary layer dynamics will also be conducted. Amplitude and arrival time anomalies for S waves from intermediate and deep focus earthquakes will be modeled by three-dimensional methods to help constrain the velocity structure and fate of deep slab downwellings. The effects of these downwellings on phase equilibria in the mantle will be examined using waveform-stacking methods that detect and characterize velocity and impedance contrasts in the mantle around subducting slabs. Complex velocity heterogeneity near the core-mantle boundary will be analyzed using new digital data sets and a hybrid 2D/3D wave propagation method that has recently been developed at UCSC.