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Developing an Empirical Relationship Between Different Distances Metrics for Seismic Hazard Assessment

The seismic hazard of an area is determined based on the ground motion observed at that site. The intensity of the ground motion can be predicted using Ground motion models (GMMs). These equations are generally developed based on the rupture model, which uses distances such as Joyner-Boore distance (RJB) and Rupture distance (RRUP). However, Probabilistic Seismic Hazard Analysis (PSHA) utilizes point-source based distances like Epicentral distance (REPI) and Hypo-central distance (RHYP), where the fault geometry may not be known. To obtain an accurate seismic hazard of an area, we need to determine the relationship between the distance metrics from these two different models. In this study, we develop empirical relationships between various distances to convert from one distance to another. This avoids conducting computationally intensive tasks such as computing finite-fault-based distances for different fault geometry of a virtual rupture plane for each point source and vice versa. The empirical equations provide the relation between two distance metrics (RJB and RHYP, RRUP and REPI, etc.) based on the magnitude of the earthquake and the dip angle of the fault. We also discuss methods to include the variability due to the conversion of the distance metrics in the PSHA. We have compared the results with previous equations developed by various researchers and found a good fit. The equations developed in this paper can be directly applied in PSHA and is independent of the GMMs used for seismic hazard calculations. Furthermore, the equations developed in this study can also be used for different fault geometries with a range of dip angles varying from 10° to 90°, different magnitude earthquake events ranging from 4.0 to 8.0 and a distance upto 1000 km.

Session: Rethinking PSHA: Are We Using Appropriate Inputs for the End Goal? IV

Type: Oral

Room: Grand A

Date: 4/21/2022

Presentation Time: 05:30 PM Pacific

Presenting Author: Melish Kayastha

Student Presenter: Yes

Additional Authors