Multi-scale surface wave analysis for the crustal and uppermantle structure beneath the southern Korean Peninsula

Abstract:

The Korean Peninsula has a complex tectonic history since the Precambrian. However, the relationship between the surface geology and the deep structure is still unclear. In this study, Rayleigh wave dispersions are measured from three different datasets to better constrain the entire crust and uppermantle. First, 3-month continuous data recorded in 150 accelerograph stations are used. From the analysis of the ambient noise cross-correlation, group and phase velocities are measured in the period-range of ~1-6 second. Second, group and phase velocities are measured for 3-30 second using ambient noise data from 30 broadband stations. Lastly, phase velocity dispersions of teleseismic data are measured for longer periods (~20-100 s) using the two-station method. We check the reliability of the dispersion measurements by comparisons between the results of different datasets within overlapping wave periods. To construct a three-dimensional model, a series of one-dimensional inversion is performed using the dispersion data extracted from tomographic dispersion maps. We use a recently developed method of the Bayesian inversion, in which S-wave velocity and thickness of each layer are searched. The obtained three-dimensional S-wave velocity model shows that the variation of velocity agrees with the major tectonic regions at shallow depths (< 5 km). In the middle crust, high velocity anomaly is found in the southeastern part of the Peninsula where the particularly low velocity is estimated at the shallow depths. At around Moho depth, the pattern of velocity variation indicates isostatic equilibrium of the Korean Peninsula. In the uppermantle, low velocity anomaly is imaged along the eastern margin of the Peninsula. The estimated model provides evidence of that the Korean Peninsular is generally homogeneous but locally modified, particularly in the southeastern part.