Assessment of Space–Time Hazard of Large Aftershocks of the 2008 Mw7.9 Wenchuan Earthquake

To adaptively forecast forthcoming large aftershocks of the 2008 Mw7.9 Wenchuan, China, earthquake, we construct a new hazard model to describe the occurrence rate of aftershocks in a study region along the Longmenshan fault. The model is denoted by SRJ since it is a combination of the Reasenberg–Jones (RJ) model and a spatial hazard model that is obtained by taking a reference of previous earthquakes in the study region. We employ the maximum likelihood (ML) method to estimate the SRJ model based on aftershocks that occurred within 1 or 2 days after the Wenchuan earthquake. The probabilities of M ≥ 5.0 aftershocks at each of the grids in the study region during next few days are then computed according to the estimated SRJ model, and hence the corresponding relative aftershock hazard (RAH) map is constructed. Finally, according to a variety of criteria for evaluating the hazard maps on depicting possible rupture area of forthcoming large aftershocks, the SRJ-based RAH map is demonstrated to be more efficient than the RAH maps constructed based on the RJ model incorporated with the gridding method using a fixed radius or varying radii.