A comprehensive model of postseismic deformation of the 2004 Sumatra-Andaman earthquake deduced from GPS observations in northern Sumatra

Endra Gunawan, Takeshi Sagiya, Takeo Ito, Fumiaki Kimata, Takao Tabei, Yusaku Ohta, Irwan Meilano, Hasanuddin Z. Abidin, Agustan, Irwandi Nurdin, Didik Sugiyanto

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)

Abstract

We investigate the postseismic deformation of the 2004 Sumatra-Andaman earthquake (SAE) using 5years of Global Positioning System (GPS) data located in northern Sumatra. Continuous GPS data from northern Sumatra suggest that the relaxation time in the vertical displacement is longer than horizontal displacements. This implies that there are multiple physical mechanisms that control the postseismic deformation, which refer to afterslip and viscoelastic relaxation. In this study, we introduce an analysis strategy of postseismic deformation to simultaneously calculate multiple mechanisms of afterslip and viscoelastic relaxation. The afterslip inversion results indicate that the distribution of the afterslip and the coseismic slip are compensatory of each other. Also, afterslip has a limited contribution to vertical deformation in northern Sumatra. In our rheology model, we use a gravitational Maxwell viscoelastic response and the result indicates that the elastic layer thickness is 65±5km and the Maxwell viscosity is 8.0±1.0×1018Pas. We find that afterslip plus Maxwell viscoelastic relaxation are appropriate to explain the deformation in northern Sumatra. We also find that our rheology model reproduces the long-term features of the GPS time series in Thailand. Applying our rheology model to the data in Andaman Islands our afterslip estimation is located at the down-dip part of the plate boundary. Finally, we showed that our rheology model is applicable to the GPS datasets of postseismic deformation of the 2004 SAE located in northern Sumatra, Thailand, and Andaman-Nicobar, respectively.

Original languageEnglish
Pages (from-to)218-229
Number of pages12
JournalJournal of Asian Earth Sciences
Volume88
DOIs
Publication statusPublished - 2014 Jul 1

Keywords

  • Afterslip
  • Postseismic deformation
  • Viscoelastic relaxation

ASJC Scopus subject areas

  • Geology
  • Earth-Surface Processes

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