Rupture features of the 2010 Mw 8.8 Chile earthquake extracted from surface waves

Abstract

This study used the rupture directivity theory to derive the fault parameters of the 2010 Mw 8.8 Chile earthquake on the basis of the azimuth-dependent source duration obtained from the Rayleigh-wave phase velocity. Results revealed that the 2010 Chile earthquake featured asymmetric bilateral faulting. The two rupture directions were N171°E (northward) and N17°E (southward), with rupture lengths of approximately 313 and 118 km, respectively, and were related to the locking degree in the source region. The entire source duration was approximately 187 s. After excluding the rise time from the source duration, the northward rupture velocity was approximately 2.02 km/s, faster than the southward rupture velocity (1.74 km/s). On average, the rupture velocity derived from this study was slower than that estimated from finite-fault inversion; however, several historical earthquakes in the Chile region also showed slow rupture velocity when using low-frequency signals, as surface waves do. Two earlier studies through globalpositioning-system data analysis showed that the static stress drop of 50-70 bars for the 2010 Chile earthquake was higher than that for subduction-zone earthquakes. Hence, a remarkable feature was that the 2010 Chile earthquake had a slow rupture velocity and a high static stress drop, which suggested an inverse relationship between rupture velocity and static stress drop.

Expanding the Range of Back-Projections: Core Phase Approach for Southern Hemisphere Earthquake Imaging

“…Our PKIKP phase BP results are consistent with BP results resolved by direct P phase BP (Figure 3b, d;and Koper et al, 2012) in terms of the north branch length and direction. However, published studies show discrepancies in the rupture direction, length, and speed for the south branch (Koper et al, 2012;Zhang, 2018;Palo et al, 2014;Huang et al, 2017). By comparing our BP results from PKIKP and P phases, we find that the former resolves a clearer south branch (Figure 3a, c).…”