Communicating Aftershock Forecasts for Situational Awareness During Humanitarian Response

Nicholas J. van der Elst, Sara K. McBride, Jeanne L. Hardebeck, Andrew J. Michael, & Morgan T. Page

Published August 12, 2021, SCEC Contribution #11307, 2021 SCEC Annual Meeting Poster #258

The USGS provides aftershock forecasts to USAID Bureau of Humanitarian Assistance (BHA) after major international earthquakes to promote situational awareness when a US response may be required. The forecasts are based on the Epidemic-Type Aftershock Sequence model and are generated using interactive software developed with BHA support. Work remains to improve the forecast communication. In particular, recent experience has highlighted the need for spatial context; it is often unclear whether the forecast applies to locations some distance from the mainshock. Such context could be as simple as a map of the aftershocks so far, or as complicated as a map showing possible shaking levels in the region.

We are now tailoring a suite of forecast products for routine delivery to BHA. The forecast suite is organized into tiers, with the idea that disaster response personnel will gain familiarity with the types of information the USGS can provide, and USGS will receive feedback on which information is actually used. Forecast Tier 1: A single summary probability, e.g. the chance of a magnitude 5 aftershock ¬– large enough to be of societal concern, small enough to be reasonably likely. This tier will include a geographic description or map of aftershocks that have occurred so far for context. Tier 2: Narrative forecast scenarios, describing three possible outcomes in terms of the size of the largest aftershock, including the worst-case where the first earthquake is a foreshock. Tier 3: A graphical summary of aftershock probabilities sorted by magnitude and forecast duration. This provides a visual summary of the hazard in terms of small and large aftershocks over a range of timeframes. Tier 4: A more detailed text version of the previous tier that includes the possible numbers of aftershocks, ready for quantitative use. Tier 5: A map of the probability of experiencing potentially damaging shaking in the surrounding region. This could be a first-tier product if adequately communicated, and continued evaluation will inform future developments.

Presenting the forecast in a tiered manner will hopefully allow a user to delve only as deep as necessary to meet their emergency response or public communications needs. Ultimately, the goal is to deliver a streamlined, minimal product that is optimized based on use.

Key Words
operational aftershock forecasting, science communication

Citation
van der Elst, N. J., McBride, S. K., Hardebeck, J. L., Michael, A. J., & Page, M. T. (2021, 08). Communicating Aftershock Forecasts for Situational Awareness During Humanitarian Response. Poster Presentation at 2021 SCEC Annual Meeting.

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