Automated determination of magnitude and source length of large earthquakes using backprojection andPwave amplitudes

Abstract

Fast estimates of magnitude and source extent of large earthquakes are fundamental for disaster mitigation. However, resolving these estimates within 10–20 min after origin time remains challenging. Here we propose a robust algorithm to resolve magnitude and source length of large earthquakes using seismic data recorded by regional arrays and global stations. We estimate source length and source duration by backprojecting seismic array data. Then the source duration and the maximum amplitude of the teleseismic P wave displacement waveforms are used jointly to estimate magnitude. We apply this method to 74 shallow earthquakes that occurred within epicentral distances of 30–85° to Hi‐net (2004–2014). The estimated magnitudes are similar to moment magnitudes estimated from W‐phase inversions (U.S. Geological Survey), with standard deviations of 0.14–0.19 depending on the global station distributions. Application of this method to multiple regional seismic arrays could benefit tsunami warning systems and emergency response to large global earthquakes.

Supershear Rupture During the 2021 MW 7.4 Maduo, China, Earthquake

“…The resulting multi-array back-projection results are shown in Figures 2d-2f. According to the obtained HF source time function (Figure 2d) and the empirical method proposed by Wang et al (2017), the rupture duration was estimated to be 38 s. As shown in Figure 2e, the earthquake ruptured toward both east-southeast (ESE) and west-northwest (WNW). The ESE rupture propagated approximately 90 km away from the initial rupture point with an average velocity of 4.0 km/s which exceeds the 3.5-km/s local S wave velocity (Bassin et al, 2000).…”

The 2018 MW 7.5 Papua New Guinea Earthquake: A Dissipative and Cascading Rupture Process

“…Figure 2 shows the imaged spatiotemporal migration of the radiated high-frequency sources. According to the empirical method proposed by Wang et al (2017) and the high-frequency source time function as shown in Figure 2b, the lower limit of the rupture duration time is estimated to be approximately 53 s. The rupture process can be divided into three stages based on the spatiotemporal features (Figures 2c and 2d). In the first stage (0-14 s), the rupture propagated southeastward approximately 25 km away from the initial point and had an average velocity of 1.9 km/s.…”

Near-Real-Time Loss Estimates for Future Italian Earthquakes Based on the M6.9 Irpinia Example

“…Back projections of the rupture line source [17] and estimates of early warning [18] may become available in near-real-time. This will replace the need to rely on aftershocks to estimate the rupture direction and length.…”