A Transient in Surface Motions Dominated by Deep Afterslip Subsequent to a Shallow Supershear Earthquake: The 2018 Mw7.5 Palu Case

N. Nijholt, W. J.F. Simons, J. Efendi, D. A. Sarsito, R. E.M. Riva

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Abstract

The 2018 (Formula presented.) Palu earthquake is a remarkable strike-slip event due to its nature as a shallow supershear fault rupture across several segments and a destructive tsunami that followed coseismic deformation. GPS offsets in the wake of the 2018 earthquake display a transient in the surface motions of northwest Sulawesi. A Bayesian approach identifies (predominantly aseismic) deep afterslip on and below the coseismic rupture plane as the dominant physical mechanism causing the cumulative, postseismic, surface displacements whereas viscous relaxation of the lower crust and poro-elastic rebound contribute negligibly. We confirm a correlation between shallow supershear rupture and postseismic surface transients with afterslip activity in the zone below an interseismically locked fault plane where the slip rate tapers from zero to creeping.

Original languageEnglish
Article numbere2020GC009491
Number of pages16
JournalGeochemistry, Geophysics, Geosystems
Volume22
Issue number4
DOIs
Publication statusPublished - 2021

Keywords

  • afterslip
  • Bayesian inference
  • GPS
  • postseismic deformation
  • strike-slip fault
  • Sulawesi

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