The influence of focal mechanism on seismic radiation energy estimation

The measurement of radiated seismic energy has long been an important aspect of seismological studies. In this work, broadband teleseismic P-wave recordings from the China National Seismic Network and Global Seismograph Network were used to measure the radiated seismic energy and energy magnitude of 105 shallow earthquakes in and outside China （M_W≥6.0 for the former and M_W≥6.5 for the latter） that occurred during 2014–2019. These measurements were then used to study the effects of focal mechanism on seismic radiation energy estimation. The following findings were obtained: ① Radiated seismic energy varies widely depending on the focal mechanism. Strike-slip earthquakes have the greatest impact on radiated seismic energy （with an average increase in energy magnitude of 0.34）, followed by normal earthquakes （with an average increase in energy magnitude of 0.08）, and thrust earthquakes （average increase in energy magnitude of 0.05）. ② The differential magnitude ΔM also varies with the focal mechanism, and the ΔM values of strike-slip, normal, and thrust earthquakes are 0.31, 0.21, and 0.08, respectively. Therefore, strike-slip earthquakes have the highest efficiency in terms of radiated seismic energy, followed by normal and thrust earthquakes. ③ Based on measurements of the 2014 Ludian earthquake, if the energy-to-moment ratio and slowness parameter are both higher than the global average, there is a chance for severe damage to occur, even at small seismic magnitudes. ④ Because the energy magnitude M_e and moment magnitude M_W reflect the dynamic and static attributes, respectively, of a seismic source, combined measurements of M_e and M_W are profoundly important for seismic danger estimation and earthquake response planning.