Environmental Response Removal and Pre-earthquake Anomaly Extraction of Borehole Strain Data

In borehole strain observation, the strain response caused by solid tide, air pressure, water level and other environmental factors will annihilate the pre-earthquake strain anomaly generated by the seismogenic process. Based on the Time Series Decomposition to remove borehole strain data of long-term trends and cycles, further on the basis of air pressure and water level is negatively related to the strain data of real-time characteristics of the Multi-channel Singular Spectrum Analysis of strain caused by removal of water level and pressure response, extract anomalies before earthquake. Take the Lushan earthquake as an example, between January 2011 and January 2014 in the response of strain data, the results show that the water level and its strain response of the correlation coefficient is -0.97, the effect of pressure is short-term, three years daily air pressure and its strain response of the absolute value of correlation coefficient is greater than 0.9 the number of days with 96%. By analyzing the negentropy anomaly of the strain data before Lushan earthquake after removing the environmental response, it is found that the abnormal cumulative acceleration phenomenon occurred 4-6 months before the earthquake.