10:45 AM - 12:15 PM
[SSS03-P05] Determining Hypocenter of 5 earthquakes in South Korea using the 3D velocity structure model
Keywords:Hypocenter determination, 3-D velocity model, nonlinear method
The extent, direction, and formation of subsurface fault can identify the earthquake magnitude and the degree of damage. Analyzing earthquakes occurring at a fault plane can predict the precise structure of the subsurface fault. Determining a hypocenter is affected by a velocity model that reflects the properties of the medium according to the ray path. Through a 3-D velocity structure model, it is possible to improve the accuracy of the hypocenter determination by improving the exact velocity structure required for seismic analysis. This study researched to determine the hypocenter using the 3-D velocity model, one of the results of the subsurface fault and velocity structure model project. The 3-D velocity model is constructed based on the ambient noise tomography applied with the Vp/Vs average ratio. We determined the hypocenter using the velocity models (1D and 3D) and the analysis data (phase arrival time) of the Korea Meteorological Administration(KMA) about five earthquakes that occurred recently in South Korea and compared our result with KMA and previous research. The hypocenters were determined by the NonLinLoc (Lomax et al., 2000), a nonlinear method applied to calculation of posterior probability density. Our hypocenter result of the 2017 M5.5 Pohang earthquake is better constrained as the result of the Korean government commission. The change of epicenters of 5 recent earthquakes using the 3-D velocity model was not shown distinctly, but the depth for each earthquake is lower except for sea earthquakes. Our result indicates that using a 3-D velocity model for the hypocenter can be more enhanced than a 1-D velocity model.