超导重力测量数据中地震事件的频域特征信息分析

Frequency domain characteristic information of seismic events in superconducting gravity measurement data

超导重力仪观测数据精度可达0.1μGal(1μGal=10^(−8) m/s^(2)),是获取地震重力信号频域特征的重要依据。本文利用中国计量科学研究院iGrav-012超导重力仪观测数据,基于谱分析探究地震事件发生前后重力场扰动信号的优势频段随震级和震中距的变化特征。研究表明:4级以上远震中,震级和震中距对同震响应、震前和震后不同时窗超导重力数据优势频段的影响不显著。地震的发生对超导重力震前震后数据的频域成分有调制作用,即震前1小时和震后1小时时窗内PSD曲线的谱峰中心个数和谱峰中心频率会发生变化。同震期间超导重力数据PSD曲线的谱峰中心个数和谱峰中心频率无显著规律。这为高频次地球内部活动导致重力场变化信息的深度分析提供了新的认识,揭示了基于高精度超导重力数据频域特征分析实现地震孕育及发生过程动态监测的应用前景。

The accuracy of superconducting gravimeter can reach 0.1μGal,which is an important basis for acquiring the frequency domain characteristics of gravity changed by earthquakes.Based on the observation data of the iGrav-012 superconducting gravimeter in National Institute of Metrology,China,we performed the variation characteristics of the dominant frequency band of the gravity disturbance signal before and after the earthquake event with the magnitude and epicenter distance using the spectral analysis method.The study showed that for distant epicenters above magnitude 4,the impact of magnitude and epicentral distance on the coseismic response and dominant frequency bands of superconducting gravity data in different time windows before and after the earthquake is not significant.The occurrence of earthquakes has a modulating effect on the frequency domain components of superconducting gravity earthquake pre-and post-earthquake data.That is,the number of spectral peak centers and the spectral peak center frequency of the PSD curve in the time window of 1 hour before the earthquake and 1 hour after the earthquake will change.There is no significant pattern in the number of spectral peak centers and the frequency of spectral peak centers in the PSD curve of superconducting gravity data during coseismic periods.This provides a new understanding of the indepth analysis of gravity field change information caused by high-frequency internal activities of the Earth,and reveals the application prospects of dynamic monitoring of earthquake breeding and occurrence processes based on frequency domain feature analysis of high-precision superconducting gravity data.