Teleseismic waveform analysis of deep-focus earthquake for the preliminary estimation of crustal structure of the northern part of Korea

Crustal structures in the several areas of the northern part of Korea are estimated using the long-period teleseismic depth phase pP and the Moho underside-reflected phase pMP generated by deep-focus earthquakes. The analysis of waveform is performed through comparison of recordings and synthetics of these phases computed using a hybrid reflectivity method, WKBJ approximation for propagation in the vertically inhomogeneous mantle and the computation of Haskell propagator matrix in the layered crust and upper mantle. The pMP phase is a precursor to the surface reflection pP phase and its amplitude is relatively small. The analysis of vertical component of P, pP, and pMP provides the estimation of structure of the source side. The deep-focus earthquakes occurred at the border area of North Korea, China, and Russia are adequate for this study. The seismograms recorded at the GSN stations in Southeast Asia provide clear identification of pMP and pP phases. The preliminary analysis employs deep-focus (580 km) earthquake of magnitude 6.3 Mb of which epicenter is located at the border region between east Russia and northeast China. Seismograms after 0.01 - 0.2 Hz bandpass filtering clearly exhibit pMP and pP phases recorded on four GSN stations (BTDF, PSI, COCO, and DGAR). Shin and Baag (2000) suggested approximate crustal thickness of the region between northern Korea and northeastern China. The crustal thickness appears to be varied from 25 to 35 km that is compatible with the preliminary analysis.