表面低速层对勘探地震横波波形影响的模拟研究

模拟了地震反射SH波在一个概念性地表低速层模型中的传播过程,发现低速层会改变其波形特征,形成显著的振幅放大效应,使反射波形的主振幅放大了2．5倍。低速层改造作用使得原本相同的反射波形在地震时间剖面上产生了非常大的横向差异。这种差异在地震资料岩性解释时很容易被错误地解释为反射体性质的变化,从而对后续勘探开发造成误导。因此,研究开发出对这种波形改造作用进行校正的方法技术是有重要实际意义的。在现今勘探工业界尚无有效手段对之进行校正的情况下,实施地震测量时应尽可能避开具有这种放大效应的地段。不然,在数据解释阶段必须充分重视这种波形变化和振幅放大效应的影响,以免做出错误的岩性解释。

A MODELING OF THE EFFECTS OF GROUND SURFACE WEATHERING LAYERS ON REFLECTED SHEAR WAVES IN SEISMIC EXPLORATION

The propagation of seismic shear waves in an indicative weathering model is modelled. It is found that the weathering layers change the waveform and amplify the main amplitude by a factor of 2.5. The effects of the weathering layers on the waveforms, which is supposed to be uniform without the weathering layers, result in a significant horizontal variation in the seismic section. This variation would be mistakenly interpreted as the change of reflectors, which would in turn mislead further exploration and (developments). Therefore, it is of importance to develop techniques to calibrate the effects. Before an (effective) technique is applicable, it is desirable to avoid selecting sites with bad weathering for seismic (acquisition). Or otherwise, the possibility of reflected waveforms being distorted by weathering layers should be kept in mind to avoid making faulty interpretation.