[btilly]

I know how he knew.

There are two types of sound in rock. P and S waves. P waves are pressure waves and go faster. S waves go side to side and are a bit slower. So you cat was woken by a hiss from the P waves, which arrive a bit before the earthquake that you can feel.

See https://manoa.hawaii.edu/exploringourfluidearth/physical/oce... to verify that there are two types of waves, and the P waves arrive first.

[pezezin]

I have been living in Japan for a while, and in my experience you can feel the earthquake coming a few seconds before the big shaking start. I don't know how to describe it, it is not a sound, more like a very slight movement.

[earth2mars]

This seems like a good sensor to build for early detection. Is that what the sensors do?

[kalleboo]

Yes https://en.wikipedia.org/wiki/Earthquake_Early_Warning_(Japa...