[timeu]

Funny, when I was young my father who was a geophyisicst (now retired) took me to seismological surveys, where we hit with a hammer on a plate to generate shock waves and measure velocity (mostly for building tunnels through montains). After a hard day of physical work, my father was drawing these lines at specific points of the recorded dataset (sorry I lack the proper terms and vocabulary because it was like 20 years ago) and there are some patterns you can use to identifiy those spots but most of it was based on his intuition and years of experience. Sometimes he let me do the interpretation and all I had was the those patterns, but many times he had to correct it because of what you describe (experience, terrain, environment, etc)