Broadband Seismological Investigations of Earth Structure and Earthquake Sources

这是一个为期四年的项目，主要进行深部地球结构和震源的地震学调查。利用现代数字地震波形数据，将解决地幔动力学结构和大地震破裂过程的基本问题。在发现了板块间地震破裂持续时间的系统变化之后，将对俯冲带大逆冲断层上的小逆冲地震的震源有限性进行详细分析。平均而言，这些浅层地震事件的破裂时间是较大深度地震事件的2到3倍。确定这是由于低应力降还是低破裂速度，需要确定破裂尺寸，这将使用具有理论和经验格林函数的指向性分析。主要边界层动力学的研究也将进行。中深震源地震的振幅和到达时间异常将通过三维方法建模，以帮助约束深板下水管的速度结构和命运。这些下行流对地幔相平衡的影响将使用波形叠加方法来检测和表征俯冲板块周围地幔的速度和阻抗对比。将使用UCSC最近开发的新的数字数据集和混合2D/3D波传播方法分析核幔边界附近的复杂速度非均质性。

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.