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Implementation of Interconnected Fault Systems in PSHA: Testing Existing Algorithms in Different Tectonic Context

Description: 

Probabilistic Seismic Hazard studies aim at quantifying the recurrence of ground-motions, based on earthquake occurrence models and ground-motion models. Most source models built for PSHA integrate faults in a rigid way. Within a predefined fault, ruptures can occur on individual segments or on a combination of segments. Ruptures that would involve segments from different predefined faults are not included in the model. The source model thus most often includes only a subset of the future ruptures that may occur on the fault system. In the last decade several research groups have proposed algorithms for implementing faults in a more realistic way. The first and most well-known is the OpenSHA algorithm (Field et al. 2014; Milner and Field 2021), applied on the well-characterized fault system in California. Later on, the SHERIFS algorithm has been proposed (Chartier et al. 2017, 2019), it is simpler than OpenSHA and requires less input parameters. Both algorithms rely on the concept of interconnected fault systems, with rules established to defined which combinations of segments are possible, as well as different techniques to distribute the moment rate budget available in the system over the different earthquake ruptures. We analyze the potential of these algorithms over fault systems with varied levels of deformation: the Sumatran fault system (~15 mm/year), the Levant fault system (~4-5 mm/year), the Java Back-Arc Thurst Fault (~1-2 mm/year). We aim at understanding how the algorithms use the information available in the fault system (slip rate estimates, segmentation, paleoseismic earthquakes, historical earthquakes ..) to produce a set of ruptures with associated rates. We show that the way the scaling relationship is applied (either total length or total area) has a strong impact on the hazard results. We analyze critically the source models obtained, accounting for uncertainties, as well as the hazard levels obtained. Overall, the general trend is towards a decrease of hazard values with respect to a classical implementation of faults, but in some circumstances hazard values may also increase.

Session: Assessing Seismic Hazard for Critical Facilities and Infrastructure – Insights and Challenges [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Celine

Student Presenter: No

Invited Presentation: 

Authors