A wave that is far enough from its source that its wavefront has no effective curvature, or is planar, over a short distance.
离震源足够远以致其波前在小范围内曲率很小或者就是是平面的波。
2
Distribution of favorable source rocks controls the planar distribution of gas reservoirs, and "effective reservoirs" in deep tight sands are the key to gas accumulation and production.