多震相走时和波形三维地震成像方法及在朝鲜半岛和祁连山地壳结构研究的应用

3D Seismic Tomography by Using Traveltime and Waveform of Multi-phase and Application to Crustal Structure in Korean Peninsula and Qilianshan Mt

本项成果包括：提出天然地震走时反演层析成像技术，采用下列方法使得处理结果得以改善：１）利用Ｐｇ，Ｓｇ，Ｐｍ，Ｓｍ，Ｐｎ，Ｓｎ等震相增大约束条件；２）用己有精度较高的人工地震测深结果作速度约束；３）用波形反演来修改模型，把波源，介质吸收，散射等全部物理特征集中反映在记录中，把诸多物理量开发出来互为约束，以修改后的模型再作反演，使解的稳定性大大提高；４）采用最优化过程，选择遗传算法。可以进行震源定位，走时反演，波形反演；５）得到任意深度的速度分布及从地表到Ｍｏｈｏ面的速度剖面。主要应用结果：对于朝鲜半岛南部，划分为５（沿纬度）＊６（沿经度）＊８（沿深度）块，对于中部分２８８块．得到从地表到Ｍ面的８个水平切面；中部地区沿纬度１３个二维剖面及其Ｍｏｈｏ面深度分布。上述方法也用于祁连山中东段地壳三维结构成像，加上地震台网数字记录，反演。该区属塔里木－阿拉善地块走廊过渡带与北祁连褶皱带；从剖面可看出该地块上地壳低速层厚，下地壳有一低速层。北祁连褶皱带盆地与隆起构造之间的起伏差异，显示古浪断裂与金强河断裂之间的深部差异与界线。两地区的结果表明，这些剖面对认识大地构造、地质结构的稳定性，深部事件的性质是很有益的，对地球动力?

Thiss results including; A new technique of simultaneous inversion for 3-D seismic velocity structure using Pg, Sg, PmP, SmS, Pn and Sn arrival times of 32 events with 404 seismic rays are inverted for locations and crustal structure, these is applied to the Center of the Korean Peninsula and Qilianshan Mt. 3-D seismic velocity tomography including 8-sections from earth surface to the Moho, 13 profiles along latitude and longitude, and depth distribution was determined. The velocities fluctuate strongly in the upper crust, There are big anisotrophy, bodies near north of Seoul in upper crust, implying that they may be related to deep fault system of Chugaryong an Valley. They found that there were low velocity bodies under the Kyongju area at the depth 10- 15 km, under the Youngwol area at the depth 10 km, at the Hongsung area at the depth 5-10 km, indicating that they may be related to the earthquake source of Kyongju (6/25/1997, Youngwol (12/13/1996), and Hongsung (10/07/1978),respectively. These results are also consistent with Bouguer gravity anomalies showing very complex and low velocity bodies beneath the Chugaryong Rift Valley and/or deep fault systems and the earthquake hypocenters, respectively.