Statistical analysis of the February 2018 Hualien，Taiwan，China，earthquake sequence：The features of its foreshocks，mainshocks，and aftershocks

As we know, the statistical properties of an earthquake sequence are associated with three important empirical laws in seismology: Gutenberg-Richter law for the frequency-magnitude distribution, Båth law for the magnitude of the largest aftershock, and the modified Omori’s law for the temporal decay of aftershocks. In this paper these three laws are combined to study the February 2018 Hualien, Taiwan, China, earthquake sequence. In addition, a physics-based model proposed by Dieterich is used to describe the foreshock activities. The Hualien aftershock sequence is divided as three major sequences compounding with the M_L5.5 foreshock sequence, the M_L5.5 aftershock sequence and the M_L6.0 sequence. The results indicate that the b values associated with Gutenberg-Richter law for the M_L5.5 aftershock sequence and the M_L6.0 aftershock sequence are approximately 1, respectively. And b value of the M_L5.5 foreshock sequence are approximately 0.5. The p values with associated modified Omori’s law for the M_L5.5 and M_L6.0 aftershock sequences are both approximately 0.9, respectively. The estimated maximum aftershock magnitudes based on the modified form of Båth law are about M_L5.0 and M_L5.5, respectively, for M_L5.5 and M_L6.0 aftershock sequences, and the magnitude error is within $\Delta M$＝0.1 with a comparison to the recorded events. We also find that, for the M_L5.5 foreshock sequence, the seismicity rate ${\dot N}$ increases as a function of 1/（t_m−t）, where t （$t {\text{＜}} {t_{\rm{m}}}$） is the time of the foreshock and ${t_{\rm{m}}}$ is the time when the M_L5.5 earthquake occurred, respectively, which is consistent with the Dieterich earthquake triggering model, suggesting that the foreshock sequence may be related with mainshock nucleation process.