Physics-based broadband ground motion simulation of the 2016 M 5.8 Gyeongju, South Korea, earthquake, using slip-weakening distance heterogeneity

The Korean Peninsula, located on the eastern margin of the Eurasian plate, has historically exhibited the low seismicity characteristic of intra-plate regions. However, the 2016 M 5.8 Gyeongju earthquake, the largest instrumentally recorded inland earthquake in the region, challenged the perception of the peninsula as a seismically safe zone. This event underscored the need for comprehensive seismic hazard assessment and mitigation strategies. Understanding ground motion characteristics of future large earthquakes is critical for advancing these efforts. Recently, physics-based broadband ground motion simulations using dynamic rupture models have gained popularity for studying near-source strong ground motion characteristics. In this study, I performed broadband (0.1–10.0 Hz) ground motion simulations of the 2016 Gyeongju earthquake using dynamic rupture modeling with the slip-weakening friction law on high-performance computing platforms. To enhance the heterogeneity of rupture processes and generate high-frequency (> 1 Hz) ground motions, I incorporated heterogeneity in the slip-weakening distance, modeled using the von Karman distribution. The distribution was controlled by three key input parameters: correlation length, Hurst exponent, and standard deviation. Preliminary results indicate that incorporating heterogeneous slip-weakening distances produces higher-frequency ground motions compared to homogeneous models. However, the simulated high-frequency energy remains insufficient to match the observed data fully. This highlights the importance of further refining physics-based broadband ground motion simulation methods to support advanced seismic hazard assessments. Future work will explore a broader parameter space for the heterogeneity of dynamic rupture parameters, including stress drop, strength excess, and slip-weakening distance. Additionally, the developed dynamic rupture models could be used to derive pseudo-dynamic rupture models, leveraging the source statistics of key kinematic parameters. These efforts aim to establish a robust physics-based broadband ground motion simulation platform for improved seismic hazard evaluation.