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四川盆地是一个构造复杂的大盆地,在这样的地区进行地震连片作图,首先必须做出准确的速度平面图。编制四川盆地速度平面图的速度数据是根据下式■计算的,即先将要计算的合成平均速度点展布在各层的层速度图和等厚图上,然后读取各点从地面出露地层至志留系各层的层速度和厚度值,由上式计算各点的平均速度值。合成平均速度点的疏密主要由作图比例尺而定,在构造复杂的部位应适当地加密,以便控制速度的横向变化。用这种方法计算出的平均速度编制的速度平面图,用于四川盆地构造连片,不但提高了作图的效率而且还提高了图件的精度。
The Sichuan Basin is a large, complex basin. To map seismic patches in such areas, an accurate velocity plan must first be made. The velocity data for the preparation of the velocity map of the Sichuan Basin are calculated according to the following formula, that is, the composite average velocity point to be calculated is first spread on the layer velocity maps and the isopachograms of each layer, and then the points are read to reveal the formation from the ground To Silurian layers of the velocity and thickness of the value from the above formula to calculate the average velocity value of each point. The density of the composite average velocity points is mainly determined by the mapping scale and should be appropriately encrypted at the points of complex structure in order to control the lateral variation of the velocity. Using this method to calculate the average speed of the preparation of the speed plan, for the construction of contiguous Sichuan Basin, not only improve the efficiency of the drawing but also improve the accuracy of the map.