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本文分析了2004年12月26日苏门答腊-安达曼地震的宽频带地震图。目的是通过不同频率成分的子事件的发生时间了解断层的破裂过程。具体分析的是由相应宽频带地震记录得到的P波的时频地震图。分析结果说明,在S波到达前的时窗内发生了最大辐射强度的相应频率低于1 Hz的15次较大子事件,但在同样的时窗内,还发生了最大辐射强度的频率更高的数百次小事件,形成了准连续的次声频率的蜂鸣声,在远至8 000 km的距离上都还能观测到。由于高频波在射线传播路径上存在较强的吸收,因而可以断定,地震期间有一大部分的地震能量是以蜂鸣声的形式被释放了。
This paper analyzes the broadband seismogram of the Sumatra-Andaman earthquake on December 26, 2004. The purpose is to understand the rupture process of faults by the occurrence time of sub-events of different frequency components. Specifically analyzed is the time-frequency P-wave seismic image obtained from the corresponding broadband seismic records. The analysis results show that the 15 largest sub-events with the corresponding maximum frequency of radiation below 1 Hz occurred within the time window before the arrival of the S wave. However, in the same time window, the frequency of the maximum radiation intensity Hundreds of high, small incidents led to the formation of quasi-continuous infrasonic beeps that were still visible up to a distance of 8,000 km. Due to the strong absorption of high-frequency waves in the ray propagation path, it can be concluded that a significant fraction of the seismic energy is released in the form of a buzzing sound during the earthquake.