Hi.
I actually study Geology at keele university. Staffordshire. One of my favorite parts of this subject is Seismic events.
Some research I am currently working on is that of infrasound. (the vibrations between 0.1hz and 20hz) This is generally what you speak of, that animals can hear these sounds where our level of hearing is only 20hz and above.
Furthermore, some animals that cannot hear these frequencies can hear the sounds made by other animals who can and as such act accordingly.
Furthermore, prior to some earthquakes you can have increased releases of gas, which again some types of animals can tell.
Incidentally, a lot of other people can 'feel' these vibrations but do not act upon them.
An experiment carried out in the last quarter of the last century had a peace of classical music, laced with infra sound and peoples experiences recorded. These ranged from fear and anxiety, to sadness and a feeling of being watched. Generally the body resonates at a certain frequency (I believe 19hz) if a combined frequency matches this at a large enough power. The body goes through various chemical changes in the brain and elsewhere. This ranges from an increased amount of endorphins creating pleasure to other reactions creating fear. Thus, knowing these feelings can give a good indication that an earthquake as either happened or is about to.
Since infra sounds discovery, various weapons have been made utilizing these frequencies such as the phaser pain Field generator. At strong enough levels can even cause matter to explode. (I'm currently making one)
Anyway going off the subject, prior to any large earthquake and post event you have seismic activity, this activity can be measured but also heard via specialist equipment or in the case of animals, naturally.
I hope this answers your question and is of some use to you.
Kindest regards
Sean
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