When earthquake happens, P-wave (Primary wave: a relatively small vertical wave) reaches first, and then S-wave (Secondary wave: a larger horizontal wave) reaches. EEW (Earthquake Early Warning System), uses this time lag to detect when the S wave (stronger shake) arrives. Let's have a look into P-wave and S-wave by creating your own earthquake wave experimental model.

ERI open house
http://www.eri.u-tokyo.ac.jp/panko/

NOTE:
- No subtitles. This lecture was conducted only in Japanese.