The Effect of Catalog Lead Time on Earthquake Forecasting Using the EEPAS Model

Sepideh J Rastin, David A. Rhoades, & Annemarie Christophersen

Published August 10, 2020, SCEC Contribution #10325, 2020 SCEC Annual Meeting Poster #102

‘Every Earthquake a Precursor According to Scale’ (EEPAS) is a catalog-based model to forecast earthquakes within the coming months, years and decades, depending on magnitude. EEPAS performs well for seismically active regions including California and New Zealand (NZ). It has been formally evaluated in Collaboratory for the Study of Earthquake Predictability (CSEP) testing centres. It has provided the medium-term component of hybrid earthquake forecasts and time-varying probabilistic seismic hazard models in NZ for nearly a decade.

The starting time of the earthquake catalog affects the performance of the EEPAS model. The EEPAS model is based on the observation that seismicity increases prior to major earthquakes. This increase follows predictive scaling relations. For larger target earthquakes the precursor time is longer and precursory seismicity may have occurred prior to the start of the catalog. The lead time is defined as the time between the start of the catalog and a given target earthquake. We have developed a formula for the completeness of precursory earthquake contributions as a function of lead time and target earthquake magnitude. We have also developed a version of EEPAS that applies the same lead time to all target earthquakes. When fitted to the same NZ catalog period as previous versions of EEPAS, the maximum lead time is 35 years. Systematically reducing the lead time to three years, we refit the EEPAS parameters and measure the information gain over a time-invariant model. The fixed lead-time EEPAS model provides insights on the effect of the missing precursory earthquakes on the performance of the model. This allows us to develop a new version of the EEPAS model that compensates for the restricted catalog duration.

Citation
J Rastin, S., Rhoades, D. A., & Christophersen, A. (2020, 08). The Effect of Catalog Lead Time on Earthquake Forecasting Using the EEPAS Model. Poster Presentation at 2020 SCEC Annual Meeting.

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