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用海上多道地震数据的折射信息可以绘制出地下构造。该方法仅需要使用沿拖缆记录的折射初至所计算的浅沉积岩层的速度和厚度。本文叙述了一种两步勘探法,该法在小型计算机和一般的办公室上均可采用。这种方法简单易懂,仅需懂得折射原理。以秘鲁近海的两个勘探实例说明了这种方法。该方法的基本步骤为:第一步,计算浅沉积岩层速度,并绘出速度图;第二步,使用勾绘的速度模式解释构造。例如,构造高区呈现比较高的速度,这表明沉积岩石在上升至近地表的过程中仍“保留”埋藏、压实的情景。这种方法要求地下构造比较浅,因为折射波的探测深度一般为100～1000米,这还取决于震源能量、拖缆长度及地下速度分布。只要满足上述要求,对于大量不同沉积岩速度、不同水深、不同地震勘探系统都可以使用折射方法。这种方法特别有用,因为在地震反射资料质量很差的地区其效果很好。
Underground structures can be drawn from the refraction information of multi-channel seismic data at sea. This method only requires the use of the refraction first recorded along the streamer to calculate the velocity and thickness of the shallow sedimentary formation. This article describes a two-step exploration method that can be used on small computers and general offices. This method is easy to understand, only need to know the principle of refraction. This method is illustrated by two exploration examples of offshore Peru. The basic steps of the method are as follows: The first step is to calculate the velocity of shallow sedimentary rock and draw the velocity map. The second step is to explain the structure using the velocity pattern of the sketch. For example, the tectonically high regions present relatively high velocities, indicating that the sedimentary rocks still “retain” burial and compaction conditions as they rise to near-surface. This method requires a shallow subsurface structure because the depth of refraction is typically 100 to 1,000 meters, depending on source energy, streamer length and subsurface velocities. As long as the above requirements are satisfied, the refraction method can be used for different seismic exploration systems for a large number of different sedimentary rock velocities, different water depths. This method is particularly useful because it works well in areas of poor quality seismic reflection data.