Abstract

An Ms7.6 Chi-Chi earthquake, which ruptured the Chelungpu fault, struck central Taiwan on 20 September 1999 at 17:47 p.m. GMT. Observed data and inversion results show remarkable differences in source proper-ties between the northern and southern segments of the Chelungpu fault. In this study, the Chelungpu fault is divided into two individual segments, and each segment is approximated by a one-body spring-slider model in the presence of friction. Results show that the simple model can interpret the differences in displacements and predominant periods between the two segments. Meanwhile, the ground surface displacement of the fault is capable of reflecting behavior of the thoroughly ruptured area, consisting of numerous different asperities, while the predominant period is able to display the oscillations of a major asperity in the fault plane. However, based on ground surface data the simple model cannot explain the differences in velocities and accelerations between the two segments.

Highlights

  • J The M .6 Chi-Chi earthquake struck central Taiwan on 20 September 1999 at 17:47 p.m.GMT (Ma et al 1999; Shin 2000)

  • The earthquake resulted from an over SO-kilometer-long, east-dipping thrust fault, with a maximum vertical ground displacement of over 6 meters and with a maximum horizontal ground displacement of over 9 meters

  • All the results show remarkable differ­ ences in source properties between the northern and southern segments of the Chelungpu fault

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Summary

INTRODUCTION

J The M .6 Chi-Chi earthquake struck central Taiwan on 20 September 1999 at 17:47 p.m. At near-fault stations, Wang et al (2002) reported a lower degree of complexity of accelerograms and larger predominant periods at northern stations than at southern ones. An attempt is made to apply a one-body spring-slider model to approximate each segment of the Chelungpu fault and to investigate the differences in stress drops, predominant periods, displacements, velocities, and accelerations at the two segments. From the source rupture processes inferred by several authors (Chi et al 2001; Kilruchi et al 2000; Lee and Ma 2000; Ma et al 2000, 2001; Wu et al 2001; Zeng and Chen 2001), the whole fault plane is composed of asperities with different sizes and displacements: larger asperities with large displacements on the northern plane and smaller asperities with small displacements on the southern plane.

DISCUSSION
CONCLUSIONS

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