求助90.4seismic reflection中的一道题

我Me是个好人UID: 3724812

Because of its accuracy in outlining the Earth’s subsurface, the seismic-reflection method remains the most important tool in the search for petroleum reserves. In field practice, a subsurface is mapped by arranging a series of wave-train sources, such as small dynamite explosions, in a grid pattern. As each source is activated, it generates a wave train that moves downward at a speed determined uniquely by the rock’s elastic characteristics. As rock interfaces are crossed, the elastic characteristics encountered generally change abruptly, which causes part of the energy to be reflected back to the surface, where it is recorded by seismic instruments. The seismic records must be processed to correct for positional differences between the source and the receiver, for unrelated wave trains, and for multiple reflections from the rock interfaces. Then the data acquired at each of the specific source locations are combined to generate a physical profile of the subsurface, which can eventually be used to select targets for drilling.
19. It can be inferred from the passage that the seismic-reflection method would be likely to yield an inaccurate physical profile of the subsurface in which of the following circumstances?
　　(A) If the speed at which the wave train moved downward changed
　　(B) If the receiver were not positioned directly at the wave-train source
　　(C) If the rock on one side of a rock interface had similar elastic characteristics to those of the rock on the other side
　　(D) If the seismic records obtained for the different sources in a grid were highly similar to each other
　　(E) If there were no petroleum deposits beneath the area defined by the grid of wave-train sources
答案是C, 我选的B. 因为是infer题, 所以不知道是不是因为explicitly presented了所以错了(定位至The seismic records must be processed to correct for positional differences between the source and the receiver)
有谁帮忙justify一下嘛ヾ(⌒(ﾉ'ω')ﾉ

nbshanshanUID: 3322812

我去查了下这个的中文看原理理解了一下，这个方法叫地震反射波法
靠不同地层的 elastic characteristics形成的不同反射以探测到不同的地层
如果一个地层的和另一个地层interface的 elastic characteristics相似，那么反射波没差别，这样本来是两层不同的地层因为 elastic characteristics相似导致检测以为只有一层。

我Me是个好人UID: 3724812

nbshanshan 发表于 2017-5-31 02:17
我去查了下这个的中文看原理理解了一下，这个方法叫地震反射波法
靠不同地层的 elastic characteristics形 ...

嗯嗯, 所以就可以定位至原文这句话了:
As each source is activated, it generates a wave train that moves downward at a speed determined uniquely by the rock’s elastic characteristics.
perfect٩( 'ω' )و