中国大陆科学钻探孔区反射地震剖面的数值模拟与分析

本初步分析了苏鲁超高压变质带大陆科学钻探孔区的地震波速度结构，在此基础上对在东海孔区三维反射地震勘探过井孔的NNW-SSE主剖面和该周围地区的DH99二维反射地震剖面进行了数值模拟分析。结果表明，数值理论模拟结果与三维反射主剖面地震波到时吻合良好，模拟法能实现有效的时深转换，也表明数值模拟中采用的速度结构是合理的。东海钻井孔区实施反射地震勘测，所得地震记录剖面图是单一P波记录，在超高压变质岩区反射地震记录图中S波的影响甚微。DH99二维反射地震剖面的模拟结果表明东海孔区2000米深度以上的密度，波速结构不随深度加大而变化；而且苏鲁超高压变质岩区地表浅层的地震波速和密度较高，是高速高密地区。岩心结果反映的反射地震阻抗差大的地段，数值模拟的理论剖面上强反射面与孔区反射地震剖面图中的强反射体基本吻合．它意味着在非沉积层的结晶岩区，反射地震勘测手段是研究地下复杂结构的有效方法。数值模拟方法可以进一步提取地震反射记录信息，是利用地震反射方法研究地球构造的一种有效的方法。

Simulations of reflection seismic profile of borehole area of Chinese Continental Scientific Drilling

In the present analysis the seismic velocity structure in the borehole area of Chinese continental scientific drilling was analyzed. Numerical simulations of profiles after stacking crossing the borehole in NNW-SSE direction for a 3-D reflection seismic survey and the DH99 2-D reflection seismic survey were carried out based on the structure analysis. The results suggest that arrival times in the simulated profile coincide well with those in observed profile after stacking, and the simulation can well perform the time-depth transformation. It implies that the structure in the borehole area used in the present analysis is available. The component of P-wave dominates in the reflection seismic profile, the component of S-wave can be neglected. The medium of high velocity and high density exists in the Sulu area, the velocity does not vary with the depth increase shallower than 2000m. The depths with large wave amplitudes in the numerical simulated profile using the velocity and density determined from the well log coincide almost with strong reflectors in the recorded seismic profile after stacking. It implies that the reflection seismic survey is a available strategy investigating the structure in the Sulu ultra-high pressure metamorphosed terrace. The numerical simulation is also a useful technique for investigation the structure because it can recover much information from the reflection profile.