Time-Dependent Seismic Hazard Assessment Based on the Annual Consultation: A Case from the China Seismic Experimental Site (CSES)

We propose an interdisciplinary approach to Time-dependent Neo-deterministic Seismic Hazard Assessment (T-NDSHA) for the China Seismic Experimental Site (CSES) at a one-year time scale. The approach is based on the Neo-deterministic Seismic Hazard Assessment (NDSHA), with the “controlling earthquakes” (or “scenario earthquakes”) as defined by the Annual Consultation on the Likelihood of Earthquakes. The Annual Consultation, organized by the China Earthquake Administration (CEA), has been an interdisciplinary practice since 1972, with the output of “alert regions” with increased probabilities of strong earthquakes, featured by real forward forecasting characteristics. We take the year 2014, in which there were four strong earthquakes in the CSES region, as a showcase example to illustrate how the T-NDSHA may be conducted and evaluated. Considering the alert regions provided by the Annual Consultation, the expected strong ground motion parameters and the macroseismic intensities are mapped by the NDSHA algorithms considering the regional Earth structures and the focal mechanisms of historical earthquakes. The estimated intensities are then compared with the observed intensities produced by the actual earthquakes. Evaluation of the performance of such annual seismic hazard assessment is performed using a confusion matrix and Molchan error diagram, respectively, indicating that the combination of the NDSHA and the annual forecasting provides the emergency preparation with a ready-to-use mapping of expected intensities which outperforms random forecasting. The proposed approach provides a substantial improvement to the Annual Consultation, and it can naturally be applied to other regions where intermediate-term middle-range earthquake forecasts are available and where the need for emergency preparation are duly considered.