用接收函数方法研究中国及邻区上地幔间断面的埋藏深度

APPLICATION OF RECEIVER FUNCTION METHOD TO ESTIMATE THE BURIED DEPTHS OF DISCONTINUI- TIES IN THE UPPER MANTLE BENEATH CHINA AND ADJACENT AREA

使用中国及邻区的 1 8个数字化地震台的宽频带三分向远震记录图 ,筛选计算得到了 2 6 3条径向接收函数 ,并拾取了在 41 0km和 6 6 0km间断面上的透射转换震相P41 0 S、P660 S与P波的到时差 .通过调整各台站之下的速度模型中这两个间断面的深度 ,使理论接收函数的P41 0 S、P660 S与P波的到时差与观测值相符 ,最终确定这两个间断面的实际埋藏深度 .结果表明 ,各台站之下 41 0km间断面的平均深度为 40 3km ,具有明显的横向不均匀性和区域性 ,其中北京台、西安台、兰州台和恩施台等的埋藏深度较浅 ,琼中台、CHTO等台较深 .6 6 0km间断面的平均埋藏深度为 6 6 3km ,也存在明显的横向不均匀性 ,其中牡丹江台和MAJO台的较深 ,琼中台和HYB台的较浅 .

receiver functions were provided from three component broadband seismograms recorded in the 18 stations in China and adjacent areas for the far earthquakes. The observed arrival time differences of P 410 S and P 660 S with P were obtained in these receiver functions. The buried depths of 410km and 660km discontinuities under a station are acquired by the way of adjusting the depths of these two discontinuities in the velocity model until the theoretical arrival time differences of P 410 S and P 660 S with P well conformed to the observed. The result shows obvious lateral heterogeneity for the buried depths of 410km and 660km discontinuities. The depth of 410km discontinuity is shallower beneath BJI, XAN, LZH and ENH, but deeper under QIZ and CHTO, and the average is 403km. The average depth of 660km is 663km, deeper under MDJ and MAJO, but shallower under QIZ and HYB.