“4·20”芦山地震次声波研究

摘要

2013年4月20日北京时间8点2分,放置于成都的数字化次声监测仪实时探测并完整记录了四川省雅安市芦山7.0级地震及以后多次＞3级余震的地震次声波全波形数据.通过时间-频率分布分析方法STFT(短时傅立叶变换)对所有特征次声事件信号进行分析处理发现,芦山地震次声波具有显著的特征:(1)具有3～4 Hz的特征频率;(2)主震次声波卓越频率为3.2 Hz,时频谱峰值能量强度达到220,维持时间长达230 s;(3)该次地震的多次余震震级(Ms)与其对应次声波经STFT分析后的峰值强度值(Amax)具有良好的相关关系:Ms=0.60105 lgAmax+2.06383,其相关性系数超过0.84.次声波或将为地震、滑坡等由岩石破裂引起的地质灾害的探测和早期预警提供一种新的手段和方法.%Many infrasound events produced by the Lushan earthquake (Ms=7.0) and aftershocks (Ms＞ 3.0) in Sichuan were detected and recorded perfectly on a digital infrasonic monitoring instrument located in Chengdu City.All of the recorded infrasound events were processed and analyzed by the time-frequency distribution analysis method,that is STFT (short time Fourier transform).The analysis results show that the characteristics of the infrasound waves from the Lushan earthquake as follows.(1) The characteristic frequency ranges from ～ 3 to 4 Hz.(2) The excellent frequency of the main earthquake is about 3.2 Hz,and the max amplitude of the timefrequency distribution spectrum is about 220.Furthermore,the infrasound wave from the main earthquake lasted long time about 230 seconds.(3) The magnitudes (Ms) of many aftershocks and the max amplitudes (Amax) of the corresponding infrasound events in time-frequency spectrum have a good relationship:Ms=0.60105 lgAmax+2.06383,and the correlation coefficient is ＞0.84.Therefore,infrasound may be a new method to detect and early warn geo-disasters caused by rock failures,such as earthquake,landslide,and so on.