Statistical Assessment for the Hazard of Large Aftershocks Post to the Chi-Chi Mainshock


Real-time hazard assessment for large aftershocks from a major earthquake is usually needed for disaster relief and rescue efforts. In this paper, we employ the Reasenberg-Jones (RJ) model to describe the time-magnitude distribution of aftershocks after the Chi-Chi earthquake (M = 7.3, 1999/9/21). Both the maximum likelihood estimated RJ model and the Bayesian estimated RJ model are used to compute the probability of having at least one future M ≥ 5.0 aftershock. A probabilistic aftershock hazard map (PAHM) is also constructed for estimating the likely spatial distribution of M ≥ 5.0 aftershocks over the study region. This map gives then alarming for potential hazardous area of future M ≥ 5.0 aftershocks. Finally, we evaluate the association between the future M ≥5.0 aftershocks and the alarming obtained from the maximum likelihood estimated PAHM and Bayesian estimated PAHM, denoted by LPAHM and BPAHM, respectively. The results suggest that the LPAHM-based alarming is superior to the BPAHM-based one for locating future M ≥ 5.0 aftershocks after the Chi-Chi earthquake.

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