Fractal size and spatial distributions of fault zones: An investigation into the seismic Chelungpu Fault, Taiwan |
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| Authors: | Kenshiro Otsuki Takayuki Uduki Nobuaki Monzawa and Hidemi Tanaka |
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| Institution: | Department of Geoenvironmental Science, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan (email: );and Department of Earth and Planetary Science, Graduate School of Science, Tokyo University, Tokyo 113-0033, Japan |
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| Abstract: | Abstract The fractality of fault zones of thickness T for the 248-m-long core from a borehole penetrating the northern segment of the seismic Chelungpu Fault, Taiwan, was analyzed. The frequency curve of T shows that the fractal dimension is normal when T is smaller than a characteristic thickness T c, and it becomes abnormally large when T exceeds T c. The fractal dimensions of size and spatial distributions of T increase as the mean distribution density of T increases, which is inconsistent with the evolution laws for ordinary brittle faults. This discrepancy implies that the thickening rate of T when T is more than T c is not constant, but a decreasing function of fault displacement. The slow thickening rate is related to the elastohydrodynamic lubrication which was effective on the fault when T exceeds T c. This slip instability mechanism can explain the large, fast and smooth slip on the northern segment of the Chelungpu Fault during the 1999 Chi-Chi earthquake. |
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| Keywords: | Chelungpu Fault Chi-Chi earthquake elastohydrodynamic lubrication fault zone fractal size frequency spatial distribution |
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