Acoustic-Gravity Waves from Earthquake Sources
Acoustic-Gravity Waves from Earthquake Sources
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DOI：
10.1007/978-1-4020-9508-5_9
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发表时间：
2010-01-01
期刊：
影响因子：
--
通讯作者：
Watada, Shingo
中科院分区：
文献类型：
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作者：
Mikumo, Takeshi;Watada, Shingo
本章回顾了各种观测的甚低频，中高频大气压力波传播直接从地震源，和那些从耦合地震瑞利波和海啸波。第一类波的频率在1.2和8.3兆赫之间的观测和理论波形建模进行了详细描述。结果表明，结合实际的热结构在低层大气中高达220公里的高度与震源参数，低频波后观察到的1964年阿拉斯加地震，2004年苏门答腊-安达曼地震是声重力波产生的大规模，海底的同震垂直升降以及这些大逆冲地震扩展震源区上方海面的相关隆起和凹陷。记录波形和合成波形之间的比较提供了同震垂直形变的量及其时间常数的估计。最近，在2003年日本十胜外地震时，利用灵敏的微气压仪和同地宽带地震仪对第三类次声波进行了全面观测。两种类型的记录之间的密切比较清楚地表明，所观察到的压力变化所激发的地面运动所激发的地震瑞利波的通道。根据这些观测结果，从压力扰动与垂直地面速度的频谱比作为频率的函数，地震次声压力传递函数已经变得清楚。
This chapter reviews various observations of very low-frequency, and medium- to high-frequency atmospheric pressure waves propagating directly from earthquake sources, and those from coupled with seismic Rayleigh waves and tsunami waves. The observations and theoretical waveform modeling of the first type of waves with frequencies between 1.2 and 8.3 mHz are described in some detail. It is shown that incorporating a realistic thermal structure in the lower atmosphere up to an altitude of 220 km with seismic source parameters, the low-frequency waves observed after the 1964 Alaskan earthquake, and the 2004 Sumatra-Andaman earthquake are acoustic-gravity waves generated by large-scale, coseismic vertical uplift and subsidence of the sea bottom and associated swelling and depression of the sea surface over the extended source regions of these great thrust earthquakes. Comparison between the recorded and synthetic waveforms provides estimates of the amount and its time constants of the coseismic vertical deformation. A recent, comprehensive observation of the third type of infrasonic waves has been made at the time of the 2003 Off-Tokachi earthquake, Japan, with sensitive microbarographs together with co-located broadband seismographs. A close comparison between the two types of the records clearly indicates that the observed pressure changes are excited by the ground motion excited by the passage of seismic Rayleigh waves. From these observations, the seismic-infrasonic pressure transfer function has been made clear from the spectral ratio of the pressure perturbation to the vertical ground velocity as a function of frequency.