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.
CITATION STYLE
Ma, K. F., Brodsky, E. E., Mori, J., Ji, C., Song Teh-Ru A., T. R. A., & Kanamori, H. (2003). Evidence for fault lubrication during the 1999 Chi-Chi, Taiwan, earthquake (Mw7.6). Geophysical Research Letters, 30(5). https://doi.org/10.1029/2002gl015380
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