长白山天池火山区的谐频事件

通过对长白山天池火山地区2002、2003和2005年夏季3期流动地震观测资料的频谱分析,发现火山口附近存在一种在频率域中形态比较特殊的地震事件,其频谱由1组等间隔的谱峰构成,峰值振幅随频率缓慢变化,形态与时间域中的谐波信号相似,我们把这种地震事件称为谐频事件。在3个夏季的流动观测中,共发现38个谐频事件,且这些事件大多与震群活动有关。分析表明,谐频地震频谱中的谐波现象与震源有关,可能是岩石破裂过程中,在特殊激发条件下,裂缝壁和裂缝内部岩浆或热液的压力扰动相互作用产生的。我们认为近年来长白山天池地震活动的突然增加和谐频事件的出现与深部岩浆的侵入活动有关

HARMONIC-SPECTRAL EVENT AT CHANGBAISHAN TIANCHI VOLCANO

By analyzing seismic data recorded by temporary seismic network deployed at Changbaishan Tianchi volcanic region in the summers of 2002, 2003 and 2005, we find one type of events whose spectra appear to be special. The station-averaged spectrum of each event consists of a series of evenly-spaced narrow peaks, the amplitudes of peaks change gradually with the frequency, the shape of spectrum is quite similar to harmonic signal in time domain. We called such event as harmonic-spectral event. During the three summers, 38 harmonic-spectral events were detected, and most of them occurred in seismic swarms. Analyses show that the harmonic spectral characteristics of these events are most likely associated with seismic sources, which might be caused by interaction with crack wails and pressure disturbances within magmatic or hydrothermal fluids filled inside of cracks at special excitation conditions, during the rock rupture processes. We suggest that the apparent increasing of seismicity and emergence of harmonic events in Changbaishan Tianchi volcanic region are associated with deep magmatic intrusion activities.