Scaling Relationships between Local Magnitude, Seismic Moment, and Radiated Seismic Energy for the 18 April 2019 Xiulin, Taiwan, Earthquake Sequence: Implications for Source Non-Self-Similarity

Using local seismograms, we obtain the source parameters of the 2019 M-L 6.32 Xiulin, Taiwan, earthquake sequence to establish scaling relationships among the local magnitude (M-L), seismic moment (M-0), moment magnitude (M-w), and radiated seismic energy (E-S) for M-L<4.0 events. The key findings are as follows: (1) logE(S)proportional to 2.0M(L), which is consistent with previous studies; (2) logM(0)proportional to 1.0M(L), which leads to M-w proportional to 0.67M(L); and (3) the scaled energy (E-S/M-0) is proportional to M-0. These relationships imply that the source duration (T) should be independent of M0. Further analysis via forward waveform modeling reveals a very weak correlation between T and M-0 (i.e., logT proportional to 0.03logM0), suggesting that T should be nearly constant. These findings indicate that the source properties of the 2019 Xiulin earthquake sequence were not self-similar. In addition, the two relationships, logE(S)proportional to 2.0M(L) and logM(0)proportional to 1.0M(L), suggest that E-S/M-0 should increase with M0 rather than E-S/M-0 tending to be a constant.