[1]ZHU jie.Anomalies of Microtremors Before the Yunnan Ludian MS6.5 Earthquake in 2014[J].Journal of Seismological Research,2020,43(01):64-70.
Copy
Anomalies of Microtremors Before the Yunnan Ludian MS6.5 Earthquake in 2014
Journal of Seismological Research[ISSN 1000-0666/CN 53-1062/P] Volume:
43
Number of periods:
2020 01
Page number:
64-70
Column:
Public date:
2020-01-30
- Title:
- Anomalies of Microtremors Before the Yunnan Ludian MS6.5 Earthquake in 2014
- Keywords:
- the Ludian earthquake; microtremors; low-frequency wave; precursor anomaly; polarization method
- CLC:
- P315.72
- DOI:
- -
- Abstract:
- Using the broadband digital data of the Yunnan digital seismic network Zhaotong,Qiaojia,Yanjin and Dongchuan stations about 10 days before the Ludian MS6.5 earthquake occurred on August 3,2014,this paper deals with the data by means of wavelet threshold denoising and fast Fourier transform,and studies the anomalous variation characteristics of the recorded microtremors before earthquakes,and also determines their anomalies by means of correlation coefficient method and polarization method.The variation of energy source orientation is used to distinguish the difference between the anomalous variation and the typhoon disturbance.The results show that:①The anomalous variation of microtremors at the four stations before the Ludian earthquake is consistent,and can be divided into two stages.The first stage begins about 112 hours before the earthquake,lasts 58 hours to 81 hours,and the maximum envelope value in the frequency band of 0.1～0.14 Hz gradually increases; the second stage starts about 37 hours before the earthquake,lasts 30 hours to 37 hours,and the maximum value in the frequency band of 0.1～0.14 Hz decreases sharply.Earthquakes occur when they fall to a low value and then rise rapidly.②The energy source orientation of low-frequency wave precursor anomaly is the focal area,which eliminates typhoon disturbance.③The anomalous variation energy is related to the epicenter distance,and generally shows a trend of spreading from the focal area to the surrounding area.
- References:
- -
- Similar References:
Memo
-
Last Update:
2020-01-30