由多震相走时和波形作三维地震成像(英文)

3D Seismic Tomography by Using Traveltimes and Waveforms of Multi-phase

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３２个地震，４０４条射线的Ｐｇ，Ｓｇ，Ｐｍ，Ｓｍ，Ｐｎ，Ｓｎ等震相增加约束条件；２）用已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Ｍｏｈｏ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。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，对地球动力学研究也有重要意义。

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 methods are applied to the Central and Southern parts of the Korean Peninsula. 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 an-isotrophy bodies near north of Seoul in the upper crust, implying that they may be related to the Chugaryong Rift Zone. They found that there were low velocity bodies beneath the Kyongiu area at the depth 10-15 km, the Youngwol area at the depth 10 km, and the Hongsung area at the depth 5-10 km, indicating that they must be due to the earthquake sources of Kyongju (6/25/1997), Youngwol (12/13/1996), and Hongsung (10/07/1978), respectively. These results are also well consistent with Bouguer gravity anomalies showing very complex and low velocity bodies beneath the Chugaryung Rift Valley and/or deep fault systems and the earthquake hrpocenters, respectively.