Gouge fabrics reset by thermal pressurization record stress on faults after earthquakes

Li Wei Kuo*, Hiroki Sone, Vladimir Luzin, En Chao Yeh, Ya Ju Hsu, Eh Tan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Stress on seismogenic faults provides critical information about how much elastic energy is stored in the crust and released by earthquakes, which is crucial in understanding earthquake energetics and recurrence. However, determining post-earthquake stress states on faults remains challenging because current borehole methods are rarely applicable to damaged fault zone rocks. We applied neutron texture analysis to gouge samples of the 1999 Chi-Chi earthquake in Taiwan to infer the stress state after the earthquake. Results indicate that the clay fabric within the principal slip zone is orthogonal to the fault plane, whereas outside the principal slip zone the fabric is predominantly parallel to the bedding-parallel fault plane. We suggest that the clay fabric in the slip zone was first neutralized by the coseismic fluidization caused by thermal pressurization and later re-oriented to the new direction of post-earthquake principal stress. Such stress orientation is consistent with the orientations inferred from corescale fault slip data and dislocation models constrained from global navigation satellite system displacements. If thermal pressurization is a ubiquitous process during earthquakes, gouge fabrics can be used to help probe the post-earthquake stress state of faults.

Original languageEnglish
Pages (from-to)1033-1037
Number of pages5
JournalGeology
Volume50
Issue number9
DOIs
Publication statusPublished - 2022 Sep

ASJC Scopus subject areas

  • Geology

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