Broadband Seismological Investigations of Earth Structure and Earthquake Sources

地球结构和震源的宽带地震研究

• 批准号: 0125595
• 负责人: Thorne Lay
• 金额: $ 52.5万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2006-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0125595&HistoricalAwards=false
• 关键词: Broadband; Seismological; Investigations; Earth; Structure

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.

这是一个为期四年的项目，旨在进行地球深部结构和震源的地震学调查。利用现代数字地震波形数据，将讨论关于地幔动力结构和大地震破裂过程的基本问题。随着板间地震破裂持续时间系统变化的发现，将对俯冲带中大型逆冲断裂上的极小逆冲地震的震源有限性进行详细的分析。平均而言，在较大深度，这些浅层地震的破裂时间是可比的地震矩事件的2到3倍。确定这是由于低应力降还是低破裂速度所致，需要确定破裂尺寸，这将通过理论和经验格林函数的方向性分析来进行。还将进行主要边界层动力学的研究。将用三维方法模拟中深震源地震的S波的振幅和到达时间异常，以帮助约束深板下井的速度结构和命运。这些下沉对地幔中相平衡的影响将用波形叠加方法来检验，这种方法探测和表征俯冲板块周围地幔中的速度和阻抗对比。UCSC将使用新的数字数据集和最近开发的2D/3D波传播混合方法来分析核-地幔边界附近的复杂速度不均匀。