An Interactive Web Tool to Visualize and Improve USGS Operational Aftershock Forecasts

Gabrielle Paris, & Andrew J. Michael

Published August 12, 2021, SCEC Contribution #11301, 2021 SCEC Annual Meeting Poster #257 (PDF)

The USGS Earthquake Hazards Program provides information to the public when potentially damaging earthquakes happen. The Operational Aftershock Forecasting (OAF) system (https://earthquake.usgs.gov/data/oaf/) publishes the chance of more earthquakes occurring in the next day, week, month, and year after all M5+ earthquakes in the US. OAF makes ~70 forecasts per sequence and produces ~5000 forecasts per year. Accuracy is important because the forecasts are used by emergency managers and infrastructure operators to make well-informed decisions, increasing the efficiency of emergency response. The forecasts also help increase public awareness of potential aftershock dangers, such as damaged buildings.

We are building an interactive web tool to visualize aftershock sequences and determine the accuracy of the OAF forecasts. The underlying code will be an open-source R package that interacts with the Comprehensive Earthquake Catalog (ComCat), where OAF stores its forecasts and obtains data to tune its models. The package starts with a flexible query function that allows the user to focus on the area and time period of their interest, query ComCat for earthquakes with forecasts, pull the forecast data, and retrieve seismicity in order to visualize and analyze the forecasts interactively via the web tool.

The web page will show 6 visualizations. Earthquakes with forecasts are shown on a global map and selecting an earthquake shows the aftershocks on a local map. A magnitude-time scatter plot shows magnitude type and the source network, a line plot compares the cumulative number of aftershocks to the forecast model, and a magnitude-frequency plot shows the number of earthquakes of each magnitude. We will also take the forecasts for each sequence and determine what fraction of observations are within the forecasted range. Each plot can be customized based on user choices.

Improving the plots helps seismologists understand complexities in the data. During the 2021 M6.0 Antelope Valley sequence, the new magnitude-time plot showed us that ComCat used different seismic networks and inconsistent methods for different earthquake magnitude ranges. Improved maps help seismologists evaluate the spatial region used for the forecast and improve communication with users. Comparing past forecasts to observations will help improve the OAF system. Thus, our R package will help the OAF team maintain operational awareness and provide accurate information to the public.

Citation
Paris, G., & Michael, A. J. (2021, 08). An Interactive Web Tool to Visualize and Improve USGS Operational Aftershock Forecasts. Poster Presentation at 2021 SCEC Annual Meeting.

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