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对中间放炮排列和共地面点集合,来自平的倾斜层界面的反射波的旅行时间由计算效率高的方法确定。计算效率通过以下两种方法得到:(1)根据与旅行时间数据拟合最小平方曲线通过内插特定炮检距(Source—receiver distances)情况下的旅行时间,而不是用迭代射线轨迹法,(2)应用固定震源的旅行时间曲线来确定在同一倾斜层界面上另一震源和共地面点集合的旅行时间。在后一种情况下,当应用这个方法时,所需要的附加计算是极少的。对另一震源位置和共地面点集合的旅行时间曲线事实上是利用平行射线的旅行时间和旅行距离与平的倾斜层界面的简单关系获得的。对固定震源排列来说,当旅行时间t(x)与二次曲线t(x)=a_0+a_1x+a_2x~2拟合时,获得了在第四层界面的0.95毫秒(在四层模型中)与第一层界面的9.5毫秒之间的标准偏差。当用三次曲线t(x)=a_0+a_1x+a_2x~2+a_3x~3时,这些标准偏差分别减小到0.81和3.5毫秒。对二次曲线t~2(x)=a_0+a_1x+a_2x~2来说,标准偏差分别变成2.97和0毫秒;对三次曲线t~2(x)=a_0+a_1x+a_2x~2+a_3x~3来说,标准时差分别为0.95和0毫秒。对在同一层位上的共地面点集合来说,当把旅行时间数据与一次曲线t~2(y~2)=a_0+a_1y~2拟合时,对第四层和第一层界面的标准偏差分别为0.84和0毫秒。当拟合的曲线为t~2(y~2)=a_0+a_1y~2+a_2y~4时,这些标准偏差就分别变成0.10和0毫秒。对深度约在5000呎的第三层界面的共地面点集合里与拟合的曲线(t~2(y~2)=a_0+a_1y~2曲线)的旅行时间的误差(在炮检距)达5000呎时小于0.5毫秒。对同一界面来说,误差比用于拟合曲线t~2(y~2)=a_0+a_1y~2+a_2y~4的相同炮检距上的0.1毫秒还要小得多。
Traveling time for reflected waves from a flat, inclined layer interface is determined by a computationally efficient method for the middle shot arrangement and common ground point set. The computational efficiency is obtained by the following two methods: (1) Based on the travel time for fitting the least square curve with the travel time data by interpolating specific source-receiver distances instead of the iterative ray trajectory method, ( 2) Apply fixed-source travel-time curves to determine travel times for another source and common ground point set on the same slant-layer interface. In the latter case, the additional computation required when applying this method is minimal. The travel time curve for another hypocenter location and a set of common ground points is in fact obtained using the simple relationship between the travel time of the parallel rays and the travel distance and the flat incline interface. For a fixed hypocenter arrangement, a 0.95 ms at the fourth interface is obtained when the travel time t (x) is fitted to the quadratic curve t (x) = a_0 + a_1x + a_2x ~ 2 ) And the first layer of the interface between the standard deviation of 9.5 milliseconds. When using the cubic curve t (x) = a_0 + a_1x + a_2x ~ 2 + a_3x ~ 3, these standard deviations are reduced to 0.81 and 3.5 ms, respectively. For the quadratic curve t ~ 2 (x) = a_0 + a_1x + a_2x ~ 2, the standard deviation becomes 2.97 and 0 ms, respectively; for the cubic curve t ~ 2 (x) = a_0 + a_1x + a_2x ~ 2 + a_3x ~ 3, the standard time difference is 0.95 and 0 milliseconds respectively. For the set of common ground points on the same horizon, when the travel time data is fitted to a curve t ~ 2 (y ~ 2) = a_0 + a_1y ~ 2, the relationship between the fourth layer and the first layer interface The standard deviation is 0.84 and 0 milliseconds, respectively. When the fitted curve is t ~ 2 (y ~ 2) = a_0 + a_1y ~ 2 + a_2y ~ 4, these standard deviations become 0.10 and 0 ms, respectively. The error of the travel time (at offset) from the fitted curve (t ~ 2 (y ~ 2) = a_0 + a_1y ~ 2) in the set of common ground points of the third layer interface with a depth of about 5000 feet Less than 0.5 millisecond at 5000 feet. For the same interface, the error is much smaller than 0.1 milliseconds at the same offset used to fit curve t ~ 2 (y ~ 2) = a_0 + a_1y ~ 2 + a_2y ~ 4.