A complex 660 km discontinuity beneath northeast China

We present a detailed seismic study of the 660 km discontinuity beneath northeast China using the receiver function technique. We use seismic data collected from 24 broadband stations in northeast China. Analysis of these data shows that the 660 km discontinuity is locally depressed in the region from longitude 128.0degreesE to 130.5degreesE and latitude 40.0degreesN to 44.0degreesN. and then it splits into multiple discontinuities in the surrounding regions. The complexity of the 660 km discontinuity beneath the subduction zones is probably attributable to the interaction between the upper mantle and subducted slab. We speculate that the flattening of the subducted lithosphere near the bottom of the upper mantle causes the multiple discontinuity structure, and that the slab penetrating the 660 km discontinuity into the lower mantle causes the narrow 660 km depression area. (C) 2003 Elsevier Science B.V. All rights reserved.