A PRELIMINARY STUDY OF THE FORM OF THE MOHO-DISCONTINUITY IN THE BEIJING AREA

The contours of equal depths of the Mohorovicic Discontinuity underneath the Beijing area in North China are presented in this paper. They have been obtained on the basis of the Pn-travel time data of explosions recorded by the Beijing seismic network. The procedure of computation consists of three steps:1. Correction of the Pn-travel time for unconsolidated surface layers and also for station and shot elevations;2. Determination of the time-term of every observation point (stations and explosion sites) and Vpn, using the modified time-term method;3. Finally, simulation of the Moho-Discontinuity, by a thin elastic plate and then calculate the depths.It may be seen quite obviously from the depth contours a tendency that toward the northwest in the mountainous part of the area, the Moho-Discontinuity is deeper, but shallower toward the southeast. In the direction of 72 northwest, it dips about 2.The average depth of the Moho-Discontinuity of the entire area is about 37 km. Besides, below it, the value of Vpn become more stable.