Evidence for fault lubrication during the 1999 Chi-Chi, Taiwan, earthquake (Mw7.6)

Kuo Fong Ma, Emily E. Brodsky, Jim Mori, Chen Ji, T. R.A. Song Teh-Ru A., Hiroo Kanamori

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The ground motion data of the 1999 Chi-Chi, Taiwan, earthquake exhibit a striking difference in frequency content between the north and south portions of the rupture zone. In the north, the ground motion is dominated by large low-frequency displacements with relatively small high-frequency accelerations. The pattern is opposite in the south, with smaller displacements and larger accelerations. We analyze the fault dynamics in light of a fault lubrication mechanism using near-field seismograms and a detailed rupture model. The fault zone contains viscous material (e.g., gouge), in which pressure increases following the Reynolds lubrication equation. When the displacement exceeds a threshold, lubrication pressure becomes high enough to widen the gap, thereby reducing the area of asperity contact. With less asperity contact, the fault slips more smoothly, suppressing high-frequency radiation.

Original languageEnglish
Pages (from-to)48-1 - 48-4
JournalGeophysical Research Letters
Issue number5
StatePublished - 1 Mar 2003


  • Chi-Chi Taiwan earthquake
  • Fault dynamics
  • Fault lubrication
  • Fluid pressurization
  • High slip velocity
  • Nearfield strong motion station


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