Thrust-type focal mechanisms of tectonic tremors in Taiwan: Evidence of subduction

Satoshi Ide, Suguru Yabe, Hsin Ju Tai, Kate Huihsuan Chen

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Unlike tectonic tremors in subduction zones and along transform faults, the hosting structure for tremors in Taiwan remains debated. Tectonic tremors in Taiwan have been discovered at ∼30km depth beneath the southern Central Range, which is a young and active collisional mountain belt. Here we provide the first evidence for the focal mechanism of tremor using moment tensor inversion in the very low frequency band, employing broadband seismograms stacked relative to the hypocentral time of tremor. The best solution corresponds to low-angle thrust faulting, suggesting the subduction of the Eurasian plate. This mechanism is consistent with strong tidal modulation of tremor activity but differs from the normal-type faulting that dominates regional shallow earthquakes. This result suggests vertical variations in the tectonic stress regime. Thrust faulting may be facilitated by a decrease in normal stress due to the buoyant roots of the mountain belt and local high fluid pressure. Key Points Focal mechanism of tectonic tremors first determined in Taiwan Strong tidal modulation consistent with the focal mechanism Low-angle thrust mechanism suggests slip on the plate interface

Original languageEnglish
Pages (from-to)3248-3256
Number of pages9
JournalGeophysical Research Letters
Volume42
Issue number9
DOIs
Publication statusPublished - 2015 May 16

Keywords

  • Taiwan
  • focal mechanism
  • subduction
  • tectonic tremor
  • very low frequency earthquake

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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