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

Abstract

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 (∆σ 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 ∆σ 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 ∆σ S , low E S /M 0 , and high Vr occurred at sea; the other with high ∆σ 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.

Rupture Directivity of the 2019 ML 6.3 Xiulin (Taiwan) Earthquake Estimated by Near-Field Seismograms: Implications for Source Scaling During Faulting

“…2, our results revealed that the largest subevent with MW 6.1 occurred about 3 s later than the initiation. The 𝐸 𝑠 /𝑀 0 ratio of 3.4  10 −5 also resembled the global average (3.0  10 −5 ; Ide & Beroza 2001) and was comparable with that of the 2018 Hualien earthquake (2.72  10 −5 ;Hwang et al 2019).…”

Understanding the 6 February 2018, Hualien earthquake sequence through catalog compilation

“…On 6 February 2018, an earthquake with a moment magnitude (M w ) of 6.4 hit Hualien, east Taiwan, toppling several buildings and causing more than a dozen casualties Chen et al 2019;Hwang et al 2019;Wen et al 2019). Unlike another hazardous M w = 6.4 earthquake that occurred two years ago in Meinong, Southwest Taiwan (Kanamori et al 2017;Kuo-Chen et al 2017;Lee et al 2017), the 2018 Hualien earthquake was preceded by a prominent foreshock sequence, including a M w = 6.1 event followed by more than 50 events of local magnitude M L ≥ 3.0 within 12 h that migrated southwest and upwards (Fig.…”

Radiated seismic energy from the 2021 ML 5.8 and ML 6.2 Shoufeng (Hualien), Taiwan, earthquakes and their aftershocks

“…b E S fromVenkataraman and Kanamori (2004) c E S fromHwang (2012) d E S from the IRIS DMC (2013) e E S fromHwang et al (2019) f E S fromHwang et al (2022) g E S , M 0 and M W from this study…”

“…Similarly, from the 2019 Xiulin aftershocks, the logE S -M L relationship, analyzed by Chan et al (2020), also failed to predict the E S of the 2019 M L 6.3 Xiulin earthquake (mainshock). Figure 3 also illustrates the E S values for several M L > 6 earthquakes in Taiwan (Venkataraman and Kanamori 2004;Wang, 2004;Hwang 2012;Hwang et al 2019Hwang et al , 2022; Table 1).…”

“…Therefore, the E S /M 0 ratio provides a measurement of the average stress drop on the fault. For comparison, also included in this plot are the E S of several earthquakes in Taiwan (IRIS DMC 2013; Venkataraman and Kanamori 2004;Wang 2004;Hwang 2012;Hwang et al 2019Hwang et al , 2022; also see Table 1). The blue dashed lines denote the standard deviations Figure 5 illustrates the plot of E S vs. M 0 .…”