Inchworm-like source evolution through a geometrically complex fault fueled persistent supershear rupture during the 2018 Palu Indonesia earthquake

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1016/j.epsl.2020.116449.

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Authors

Ryo Okuwaki , Shiro Hirano, Yuji Yagi, Kousuke Shimizu 

Abstract

How does fault slip follow an earthquake rupture front propagating faster than the local shear-wave velocity (i.e., at supershear speed)? How does a supershear rupture front pass through a geometrically complex fault system? Resolving the evolution of such complex earthquake ruptures is fundamental to our understanding of earthquake-source physics, but these events have not been well captured by conventional waveform inversions of observational data. We applied a new framework of finite-fault inversion to globally observed teleseismic waveforms and resolved both the spatiotemporal evolution of slip and the fault geometry of the 2018 Palu earthquake (moment magnitude 7.6) in Sulawesi, Indonesia. We show that supershear rupture propagation for this event was sustained by transient slip stagnation and advancement as the rupture front passed through the geometrically complex fault system. This peculiar inchworm-like slip evolution was caused by the rupture front encountering fault bends with favorable and unfavorable orientations for rupture propagation. Our analysis also identified the possible existence of a fault junction beneath Palu Bay connecting an unmapped primary fault in northern Sulawesi with the Palu-Koro fault in the south.

DOI

https://doi.org/10.31223/osf.io/j4cas

Subjects

Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure

Keywords

earthquake, Fault geometry, Kinematic source inversion, Supershear rupture

Dates

Published: 2020-02-21 11:05

Last Updated: 2020-05-30 19:06

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License

CC BY Attribution 4.0 International

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