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There are three types of waves that travel through the earth's crust during an earthquake at different speeds: primary, secondary and surface waves, which arriv
by asdfman123 7y ago
There are three types of waves that travel through the earth's crust during an earthquake at different speeds: primary, secondary and surface waves, which arrive in that order.
Perhaps one of the first two waves woke you up, and then the surface wave is what "felt" like an earthquake to you.
In fact, earthquake warning systems detect P-waves early, send out alarms, and give people a few seconds to stop subways and get outside before the surface waves roll in. It's not the same as earthquake prediction, though.
- saltcured 7y agoDo you how fast these waves travel versus sound in the atmosphere? Or, how these waves themselves might sound qualitatively when they shake nearby structures in the air? On more than one occasion, I think I've anticipated an earthquake based on sound. I can only describe it like an approaching but amorphous activity, a bit like when large flocks of birds take to flight over an open field or when a wind gust goes through a forest. I think I've noticed this sound only with relatively nearby epicenters (5-25 miles). The very distant ones usually seem more silent and my first recognition is the jiggle and displacement, or perhaps the creaking sounds of the surrounding structure if I am indoors.