Determination of seismic surface wave strain magnitude based on borehole strain seismic wave records

The high sampling rate borehole strain gauge, developed in recent years, can record the horizontal strain caused by seismic waves, which is a crucial method for the study of dynamic Coulomb stress. It is an important scientific topic to determine earthquake magnitude by using strain seismic waves that recorded by borehole strain gauge. In this study, strain seismic wave data recorded by four-component borehole strain gauges at ten stations in China from January to March in 2020 are collected, and a total of 68 shallow source earthquakes with magnitude 114 >= 4. 0 are selected. The strain magnitude formula obtained by using the least square method is M-epsilon = lgE(max) + 1. 651g(Delta) +1. 43. For earthquakes with magnitude M<6. 5, the strain magnitude <(M)over bar>(epsilon) calculated is basically consistent with the magnitude M-CENC published by the China Earthquake Networks Center: M-CENC = 1. 03 (M) over bar (epsilon) - 0. 23. However, the strain magnitudes of the two earthquakes with magnitude M>7. 0 in this study occur magnitude saturation phenomenon. The basic conclusion of this paper is that using strain to determine magnitude is basically feasible, but the saturation phenomenon of the two earthquakes with magnitude M>7.0 needs to be further studied. Because they contain not only the determination of earthquake magnitude, but also the study of triggering effect of dynamic Coulomb stress caused by remote earthquakes. In the future study, analyzing more borehole strain seismic wave records of large earthquakes are needed.