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本文将剖面成象技术应用于两组跨孔地震资料,来确定速度结构以及判明各种算法对买际资料的可靠性和分辨率。实验是在纽约Retsoff盐矿和瑞典Stripa矿地下放射性废料研究基地进行的。Retsoff的走时资料质量很高,并且在长度直到500m的整个射线路径上都能记到。Retsoff地区结构相当复杂,其速度差高达50％。Stripa场地位于速度差仅有百分之几的花岗岩上。实验范围不大,最大射线长度刚刚超过10m。该场地采集的资料精度很高,源和接收点位置的测量精度小于1.0mm走时的读数误差为0.001ms。本文将若干类似于医学成象的代数重建技术(ART)应用于这些资料。算法作了一些修改,例如,加权模式的应用,阻尼参数的应用,利用弯曲射线路径。所得到的速度场与已知场进行比较,相互对照以便确定一种最优方法。业已发现,这些算法是重建实际资料慢度场的一种速度可靠的方法,低速带的位置和速度值精确地被恢复原状。同时还发现,为保证利用适当的阻尼参数,取适当的叠代次数,应用这些技术时必须非常小心,否则重建技术的结果会很差。
In this paper, the cross-imaging technology is applied to two sets of cross-hole seismic data to determine the velocity structure and determine the reliability and resolution of various algorithms for the purchase data. Experiments were conducted at the Retsoff Salt Mine in New York and the underground radioactive waste research site at the Stripa mine in Sweden. Retsoff’s travel time information is of high quality and can be recorded on the entire ray path up to 500 m in length. The structure of the Retsoff area is quite complex with a speed difference of up to 50%. The Stripa site is located on granite where the speed difference is only a few percent. The experimental range is not large, the maximum ray length just over 10m. The accuracy of the data collected at the site is high, the measurement accuracy of the source and receiver locations is less than 1.0mm, and the reading error is 0.001ms. This article applies algebraic reconstruction techniques (ART) similar to medical imaging to these data. Some modifications have been made to the algorithm, such as the application of a weighted mode, the application of damping parameters, the use of curved ray paths. The resulting velocity field is compared to known fields and compared to one another to determine an optimal method. It has been found that these algorithms are a fast and reliable way to reconstruct the slow field of actual data, and the position and velocity values of the low-velocity zone are precisely restored to their original values. It has also been found that care must be taken to apply these techniques in order to ensure proper dimming parameters and appropriate iterations, otherwise the reconstruction technique will have poor results.