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Dependence of Seismic Hazard Assessment on the Observation Time Interval: Insights From Physics-Based Simulated Seismicity in Southeastern Spain

Description: 

The magnitude-frequency distribution (MFD), which defines the seismicity of a region, is obtained using the earthquake record. In slow-moving fault systems, where seismicity is low to moderate, earthquake catalogues may not cover the full seismic cycle of active faults. This implies that seismogenic sources may be incompletely characterized on Probabilistic Seismic Hazard Assessment (PSHA), since the quantification of seismic hazard is associated with the specific time period during which earthquake catalogue have been recorded. To evaluate the dependence that exists between seismic hazard and the observation interval, this study develops some PSHAs based on synthetic seismicity. The selected site is the Eastern Betics Shear Zone in SE Spain, where some damaging earthquakes have occurred. The synthetic seismicity of this fault system consists of a million-year earthquake catalogue generated using the RSQSim earthquake simulator. The digital model considers the geometry, slip rates and friction properties of major faults. From the global synthetic catalogue, ten thousand sub-catalogues have been obtained. Their duration has been selected to be equivalent to that of the actual earthquake record (i.e. 1,000 years). Each sub-catalogue shows different features in their MFDs, which can be quantified by the distribution of values of the slope of the Gutenberg-Richter relationship, the annual earthquake rate and the maximum magnitude. A hundred sub-catalogues have been randomly selected to conduct individual PSHA. Seismic hazard curves have been obtained for the cities of Murcia, Lorca, Alicante, Vera, Torrevieja and Almería using R-CRISIS. These curves reveal that each sub-catalogue leads to different return periods for specific values of Peak Ground Acceleration (PGA). The variability coefficient was used to quantify hazard variability, with a maximum value of 58% found in Torrevieja for a PGA=1g and a minimum of 10% in Almeria for a PGA=0.02g. These results show that seismic hazard depends on the time interval during which an earthquake catalogue is recorded. This dependence increases for large PGA values.

Session: Regional-Scale Hazard, Risk and Loss Assessments [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Elena

Student Presenter: No

Invited Presentation: 

Authors