中朝克拉通东部上地幔精细圈层结构：来自朝鲜核爆源深地震测深剖面的约束

Since the Late Mesozoic, the lithospheric properties of the Sino-Korean Craton have changed significantly. However, the specific form of craton "destruction" is mainly based on the investigation of surface geology, geochemistry, crustal structure imaging and the detection of low-velocity discontinuity in the upper mantle, lacking constraints on the fine structure and properties of the entire upper mantle. Therefore, based on the seismic observations from the nuclear explosion on September 3, 2017 in North Korea recorded by the national seismic network of China and some temporary broadband seismic stations, we obtain high-vertical-resolution one-dimensional VP models of the upper mantle beneath the eastern Sino-Korean Craton and its adjacent areas by using deep seismic sounding imaging method. The results reveal that the regional average crustal thickness is about 29∼30 km, and the average crustal velocity is about 6.10∼6.17 km·s^-1, which is significantly lower than the global continental average value, indicating the lower crust below these profiles is extremely thin or even missing. Thin and strong reflection coefficient across the Moho discontinuity may be caused by the existence of strong horizontal anisotropy at the base of the thin crust. An intra-lithospheric discontinuity (ILD) with small positive velocity gradient is detected at about 80 km depth. We speculate it may be caused by the phase transformation from spinel to garnet, the Lehmann discontinuity is observed at about 220 km, which usually exist below stable cratons. What's more, the velocity of the upper mantle between the ILD and Lehmann discontinuity is significantly lower than that of the global IASP91 model. The arrival times of these upper mantle seismic phases (Pn, PL and P410) are between the stable craton region and the active tectonic region, indicating that the upper mantle in the eastern Sino-Korean Craton and its adjacent areas is in a "cold" to "hot" transition state as a whole.