Crustal thickness variations in East Asia from Moho underside reflections of deep earthquakes

Thickness of crust is essential information for studying various geological and tectonic processes. Particularly in East Asia, the evolution of cratonic lithospheres, Mesozoic-to-Cenozoic extensions and riftings by subduction of oceanic plates, and the development of intraplate volcanism are of interest. To estimate the variation of crustal thickness in East Asia, we measured the time difference between the phases of the Moho underside reflection (pmP) and the surface reflection of outgoing P wave (pP) from deep earthquakes, which occurred at deeper depths by subduction of Pacfic plate under the Eurasian Plate. We select earthquakes in East Asia with magnitude greater than Mw 5.5 and depth deeper than 300 km. The vertical component of seismograms were used for stations in distance between 45-85° from the sources. Seven events are selected mainly in the border regions between North Korea, China, and Russia since 1990. Data from stations belong to GSN, FDSN, and PASSCAL networks were used. The data sample parts of northeastern China, the far east Russia and the East Sea (Japan Sea). The time differences were measured in independent seismograms and stacked ones to enhance the signal. In addition, we computed synthetic seismograms to compare with the observed seismograms. Estimated crustal thicknesses were in the range of 26-44 km in northeastern China, 30-43 km in the east Russia, and 9-17 km in the East Sea, which correspond to previous estimations, but provide more details about the variation of the Moho surface in East Asia.