摘要
从波动方程出发,推导出平面波场传播基本公式,阐述了利用地表观测波场反演地球内部波速结构的理论关系.观测波场可通过τ-p 变换分解为地表平面波场,其最大振幅的轨迹能稳定地反映出地球内部波速随深度变化的趋势,这一特征可用来对反演解空间进行约束.波场延拓技术可以充分地利用观测波场中包含的丰富信息,在迭代反演中不仅能简单快速地得到反演解,而且所得解具有良好的稳定性,较少受主观因素影响,这是一种很好的反演技术.对波场延拓进行了理论分析与数值模拟,采用了同态反褶积等改善资料信噪比的措施,使解的分辨能力得到了提高.文中对南海北部一个声纳折射剖面进行了分析和计算.结果表明:该区1.4km 深处,存在一个从1.76km/s 到2.21km/s 的速度间断面.间断面上下两层的速度梯度分别为0.54km·s^(-1)/km,0.63km·s^(-1)/km.最后,从构造演化的角度对浅海构造特征进行了探讨.
Based on wave equation a fundamentl formula for plane wave propagation is derived, the theoretical relationship of inverting wave velocity structure through the observational wave field is discussed in this paper. The observational wave field can be decomposed into the surface plane wave field by using ×-p transform. The maximum amplitude curve in the plane wave field can show stably the change tendency of wave velocity with depth in the Earth. This property can be used to restrict the solution space. By using the wave field continuation method more useful information from the observational wave field can be extracted and the inversion solution not only can be obtained simply and quickly, but also is stable and less influenced by the subjective factor. The wave field continuation is a fine inversion method.Theoretical analysis and numerical modelling are carried out in the study of wave field continuation. By applying homomorphic decovolution the signal-tonoise ratio is improved.Finaly a sonar refraction profile in the northern part of the South China Sea is interpreted and computed. It is found as a result that there is a velocity interface from 1.76 km/s to 2.21 km/s at the depth of 1.4km. The velocity gradients in the upper and lower layer are 0.54 km·s-1/km and 0.63 km·s-1/km respectively. A discussion of the characteristics of shallow sea structure in the view of tectonic movements is given.
出处
《地震学报》
CSCD
北大核心
1991年第1期41-52,共12页
Acta Seismologica Sinica
基金
地震科学联合基金会