The Physical Mechanism of Deep-Focus Earthquakes from Broadband Waveforms

这项研究是为了系统地从远震宽带波形中确定深部地震的时间震源特性，包括震源谱、地震能量、应力降、上升时间和持续时间。最近，由美国国家科学基金会支持的全球数字地震台网(GDSN)提供的宽带数字地震图提供了一组宝贵的深部地震波形数据。初步结果表明，俯冲大洋板块内10至670公里深的事件，应力降随深度或时刻没有系统性变化，尽管散布很大。然而，对于深度超过550公里的地震，上升时间会变得更短。在100至200公里深度以下，俯冲板中的压力和温度抑制了在较浅深度引起地震的脆性破坏。这项研究的目标是确定允许发生深部地震的物理过程，这是固体地球物理学中的突出问题之一。

This research is to systematically determine temporal source properties of deep earthquakes including the source spectrum, seismic energies, stress drops, rise times, and durations from teleseismic broadband waveforms. Recently available broadband digital seismograms from the Global Digital Seismic Network (GDSN) supported by NSF provide a valuable data set of waveforms from deep earthquakes. Preliminary results show no systematic change in stress drop with depth or moment for events from 10 to 670 km deep within subducting oceanic slabs, although the scatter is large. Rise times, however, become shorter for events deeper that about 550 km. Below 100 to 200 km depth, pressure and temperature in the subducting slab inhibit the brittle failure that causes earthquakes at shallower depths. The goal of this research is to determine the physical process that allows deep earthquakes to occur, one of the outstanding problems in solid earth geophysics.