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随着排列长度的增加,根据地震资料确定的均方根速度将不同于由狄克斯关系式所给出的。我们曾研究了水平界面或层速度为深度的连续函数的地层的时距曲线的性质,以及根据它们的求得的速度。我们的结论如下:(1)对于一已知的反射波,t~2—x~2时距曲线的斜率在任一距离x上都等于(V_(rms)~(-2)),这里V_(rms)是沿着一适当的射线路程算得的均方根速度。V_(rms)是由狄克斯关系式给出的速度。随着x的增加,V_(rms)(x)接近于一极限值它等于被射线穿过的地下剖面的层速度中的极大值。(2)t~2—x~2曲线表明V_(rms)是x的单调增量函数。结论(1)和(2)允许我们给出时差速度的界限。(3)如果层速度假设成
As the length of the array increases, the root mean square velocity determined from the seismic data will be different from that given by the Dixz equation. We have studied the nature of the time-history curves of strata with horizontal or continuous velocities of depth and the velocities obtained from them. Our conclusions are as follows: (1) For a known reflected wave, the slope of the t-2-x ~ 2 time-distance curve is equal to (V rms -2) at any distance x, where V_ rms) is the root mean square velocity along an appropriate ray path. V rms is the speed given by the Dix’s relationship. As x increases, V rms (x) approaches a limit equal to the maximum in the layer velocity of the subsurface cross-section through which the ray passes. (2) The t ~ 2-x ~ 2 curve shows that V_ (rms) is a monotonically increasing function of x. Conclusions (1) and (2) allow us to give the margin of time difference speed. (3) If the layer velocity is assumed to be