复杂地表条件下陡倾角勘探区地震数据采集研究

针对王家山地震勘探区具有目的层倾角大（30°～60°）、地表相对高差大、黄土覆盖层厚、地表条件十分复杂等地震难点,在前期调研的基础上,依据品质因数—地层衰减系数与纵波速度的关系,炸药震源与介质阻抗的耦合关系,虚反射与最高频率的关系等相关理论依据,提出了获得较好原始资料的保证措施：在厚黄土厚附近,炮点变观至基岩裸露区或厚度较小区域;炸药依据基岩、黄土等岩性差异分别选用铵锑成型炸药及2#岩石硝铵炸药;激发井深为虚反射界面深度、药柱长度及药柱顶部爆炸破坏带高度之和;组合激发井距大于2倍塑性带半径;接收束状砖块式10线8炮制观测系统;大倾角地层采用较大的偏移距,下倾激发方式。通过野外采集实验,证明了该复杂条件下陡倾角勘探区采取的三维地震勘探措施的合理性,经初步处理,野外采集的资料各项质量技术指标均达到规范要求,解释的浅部塌陷区影响边界由原来计算的100～200m控制到了50m范围之内,达到了非常理想的程度。

Seismic Data Acquisition Study under Complicated Surface Condition of Steeply Dipping Prospecting Area

The Wangjiashan seismic prospecting area has seismic prospecting nodi of steeply dipped（30°~60°） zone of interest,large surface relative relief,thick loess covering and complicated surface condition.Based on earlier stage investigation,in terms of Q factors-relations between strata attenuation coefficient,charge source and medium impedance feed through,ghost reflection and maximum frequency,put forward guaranteeing measures to get better primary data： near the thick loess tableland,shotpoint transferring to bedrock outcropped or thinner loess areas;according to bedrock,loess lithologic differences use ammonium-antimony packaged explosive and 2# ammonium nitrate explosive respectively;shothole depth is summation of ghost reflection interface depth,explosive cylinder length and height of cylinder top failure zone;distance between multiple-shot points larger than twice plastic zone radius;receiving bunchy brick-shaped 10line-8shot observation system;using larger offset,downdip shot mode in steeply dipping areas.Through field acquisition testing,has demonstrated the reasonableness of the measures.After initial processing,each quality technological index of field acquired data can meet code requirement.Accuracy of interpreted shallow subsidence area boundary from originally estimated 100~200m can be accurate to within 50m,thus an excellent level.