Complex fault ruptures for hazard and risk: Case studies for El Salvador and Ecuador

Jessica Velasquez, & Marleen Nyst

Published 2023, SCEC Contribution #13407

We know that complex ruptures happen in nature. Why then are they often missing in hazard and risk models? Fault mapping and characterization throughout much of Latin America and the Caribbean has made great strides in the past decade and hazard models like the Global Earthquake Model’s CCA (Styron et al., 2020) and SARA (Garcia et al., 2017) projects along with consensus models like RESIS II (Benito et al., 2012) and Alvarado et al. (2017) have helped to bring this work together for use in seismic hazard modeling. How then can we make better use of this information when it comes to modeling complex ruptures?

Complex ruptures involving multiple segments of faults or multiple faults can have a two-fold impact on hazard: (1) they can increase the maximum magnitude in a region, and (2) they push the impact of the faults involved to longer return periods as rate is distributed to these complex ruptures. The associated impact on risk is three-fold, involving both (1) and (2) from hazard as well as (3) correlating exposure that otherwise might not be correlated. Here we present examples of the impact of modeling these ruptures in El Salvador and Ecuador. We show that it is important to consider these ruptures, particularly for long return period hazard and risk, especially in areas where the fault database indicates a system of faults (e.g., El Salvador) and areas where only surficial fault information is available (e.g., Ecuador).

Citation
Velasquez, J., & Nyst, M. (2023). Complex fault ruptures for hazard and risk: Case studies for El Salvador and Ecuador. Poster Presentation at Seismological Society of America Annual Meeting. doi: 10.1785/0220230054.