Upper-crust Tomographic Structure of the Southern Korea Peninsula from Local Earthquakes

Abstract:

We derived the three dimensional P wave velocity model for the uppermost 14 km of crust in the southern Korea peninsula using travel-time data from local earthquakes which are recorded by two nation-wide seismic networks operated by Korea Meteorological Administration and Korea Institute of Geoscience and Mineral Resources. Earthquakes in the study occurred between 2001 and 2014. 19,935 P wave arrivals from 747 earthquakes observed by 184 seismic stations are selected for the 3-D tomographic inversion. In order to secure best possible data for tomography inversion, we applied a strict criteria during the selection of earthquakes and travel-times. The study area is parameterized by 10km×10km×4km grid for velocity inversion and 1km×1km×1km grid for travel time calculations. Checkerboard resolution test are used to demonstrate the ray coverage and the resolution for the given station-event configurations. The results indicate P-wave velocity model at shallow depths less than 2 km are not properly resolved mainly due to the insufficient ray coverage. The model at deeper depths greater than 14 km also suffered by lack of ray coverage. Thus, we limit our interpretations of the preliminary P wave velocity model to areas that are illuminated by enough rays. P wave velocity model indicates there are significant lateral velocity variations across the southern Korea peninsula. Most distinguished feature in the velocity model is the higher velocity anomaly beneath the southeastern Korea peninsula. The anomaly regions is distinguished by well-defined tectonic boundary. At 8 km depth, lower velocity anomaly is observed in Gyeonggi massif and high-mountain regions in the southern Korea peninsula. The 3-D velocity model is compared with geophysical and geological observations.