Multiple-event analysis of the 2018 M_L 6.2 Hualien earthquake using source time functions

• Published in: Terrestrial, Atmospheric and Oceanic Sciences Vol. 30; no. 3; pp. 367 - 376
• Main Authors: Ruey-Der Hwang, Chiung-Yao Lin, Cai-Yi Lin, Wen-Yen Chang, Tzu-Wei Lin, Yi-Ling Huang, Jo-Pan Chang
• Format: Journal Article
• Language: English
• Published: 中華民國地球科學學會 01.06.2019
• Subjects: Rupture velocity; Source time function; Static stress drop; 2018 Hualien earthquake; Multiple-event analysis
• ISSN: 1017-0839
• DOI: 10.3319/TAO.2018.11.15.01

Through forward multiple-event analysis of teleseismic P-waves using source time functions (STFs), derived by non-negative time-domain deconvolution, we inferred the rupture features of the 2018 Hualien earthquake. At least six sub-events composed the Hualien earthquake, with the largest one (corresponding to M_w = 6.3) occurring 4.8 s later than the initiation of rupture. The total seismic moment (M_0) of 6.48 × 10^(18) Nm (M_w = 6.5) and radiated seismic energy (E_S) of 1.76 × 10^(14) Nm led to the E_S/M_0 ratio ~2.72 × 10^(-5). A static stress drop (Δσ_S) of 5.03 MPa was also derived for the earthquake. On average, the rupture parameters of the 2018 Hualien earthquake from this study were similar to globally average values. From M_0 and source duration (10.9 s), this implied an average rupture velocity (Vr) less than 2.0 km s^(-1). The forward multiple-event modeling showed that Δσ_S varied with the sub-events and increased with E_S/M_0 to imply the frictional strength being heterogeneous along the fault. From the highest STF peak (6.9 s after the initiation) near the land-sea interface, we suggested that the Hualien earthquake be divided into two rupture processes. One with low Δσ_S, low E_S/M_0, and high Vr occurred at sea; the other with high Δσ_S, high E_S/M_0, and low Vr occurred on land. Both seawater and local velocity structures probably played crucial factors behind these rupture discrepancies during the 2018 Hualien earthquake.