New software for computing time dependent seismic hazard during aftershock sequences using the OpenSHA platform

Nicholas J. van der Elst, Kevin R. Milner, Edward H. Field, Sara K. McBride, & Morgan T. Page

Published August 15, 2018, SCEC Contribution #8675, 2018 SCEC Annual Meeting Poster #045

The chaos caused by a major earthquake does not end when the shaking stops. Search and rescue, damage assessment, and lifeline repairs all need to be carried out under the constant threat of damaging aftershocks. In some cases, aftershocks can be even more destructive than the initial event, as was the case in Christchurch, New Zealand in the 2010-11 earthquake sequence. While it may never be possible to predict the exact time, place, and magnitude of an impending earthquake, it is nonetheless possible to make probabilistic assessments of aftershock hazard based on past regional sequences and the specifics of an ongoing sequence. Forecasts, and in particular forecast maps, can provide situational awareness, increase public resilience, and help prioritize response and recovery operations. During times of crisis, quick production and release of these forecasts can help fill the vacuum of information and assist a variety of people in making informed decisions.

The USGS, with support of USAID-Office of U.S. Foreign Disaster Assistance, is developing several lines of aftershock forecasting products with the goal of providing rapid quantitative aftershock information to emergency managers and affected communities. Here we introduce software designed to streamline the process of analyzing and forecasting aftershock sequences within a modified Epidemic-Type Aftershock Sequence framework. Forecasts are a Bayesian combination of a regionalized generic model and a specific model tuned to the ongoing sequence as reported by ComCat. The software translates spatio-temporal rate forecasts into time-dependent probabilistic hazard estimates using standard ground-motion prediction equations. Graphical forecast summaries and hazard maps supplement standard magnitude-probability tables. This presentation will describe modifications to the ETAS model that allow for efficient and stable generation of aftershock forecasts, and discuss expected applications of the software.

Key Words
Forecasting

Citation
van der Elst, N. J., Milner, K. R., Field, E. H., McBride, S. K., & Page, M. T. (2018, 08). New software for computing time dependent seismic hazard during aftershock sequences using the OpenSHA platform. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)