反射地震零偏移距逆时偏移方法用于隧道超前预报

为了高效快速地采集到隧道开挖前方的反射地震数据并提供实时的隧道前方地质超前预报，本文提出一种基于波动方程逆时偏移原理的隧道地质超前预报方法.为了获得与该超前预报方法相适应的地震数据，本文还提出适用于隧道内有限空间环境下的PMZO（Plus Minus Zero Offset）反射地震采集方案.本研究根据理论地震记录分析了隧道中零偏移距地震记录反射波的时距关系和振幅特征，讨论了隧道中地震记录的解释方法，利用含多条断层破碎带的地质模型，模拟了基于逆时偏移算法的实时隧道地质超前预报.数值计算结果证明，PMZO数据采集方案以及逆时偏移算法可以获得隧道开挖前方地质构造的准确成像.

Zero-offset reverse time migration for prediction ahead of tunnel face

To implement fast and effective acquisition and real-time prediction ahead of tunnel face,this paper presents a reverse time migration approach to looking ahead of tunnel face based on the wave equations.A reflected acquisition scheme PMZO(Plus Minus Zero Offset)applied to a limited space in tunnel was also proposed for obtaining the seismic data that is applicable to the approach presented in the paper.We analyze the relation of reflected time-offset curves and characteristics of reflected amplitudes by using synthetic zero offset data in tunnel acquisition and discuss the interpretation for tunnel seismic data.In a model with a few faults in front of tunnel face,the numerical examples show that accurate images have been obtained ahead of the tunnel face by implementing the PMZO acquisition and the reverse time migration.