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

Abstract Using local seismograms, we obtain the source parameters of the 2019 ML 6.32 Xiulin, Taiwan, earthquake sequence to establish scaling relationships among the local magnitude (ML), seismic moment (M0), moment magnitude (Mw), and radiated seismic energy (ES) for ML<4.0 events. The key findings are as follows: (1) logES∝2.0ML, which is consistent with previous studies; (2) logM0∝1.0ML, which leads to Mw∝0.67ML; and (3) the scaled energy (ES/M0) is proportional to M0. 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 M0 (i.e., logT∝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, logES∝2.0ML and logM0∝1.0ML, suggest that ES/M0 should increase with M0 rather than ES/M0 tending to be a constant.