" If they inundate us with their products, it is because they expect to be inundated with ours in return.
The occurrence of such sounds is consistent with the passage of high-frequency seismic waves through the ground.
In mines there is frequently little damage below depths of a few hundred metres even though the ground surface immediately above is considerably affected.
Earthquakes are frequently associated with reports of distinctive sounds and lights.
The usual immediate cause of a tsunami is sudden displacement in a seabed sufficient to cause the sudden raising or lowering of a large body of water.
This deformation may be the fault source of an earthquake, or it may be a submarine landslide arising from an earthquake.
However, the amplitude (that is, the height of disturbance) at the water surface does not exceed a few metres in deep water, and the principal wavelength may be on the order of hundreds of kilometres; correspondingly, the principal wave period—that is, the time interval between arrival of successive crests—may be on the order of tens of minutes.