All earthquakes start with P waves  These P waves move fast, causing the ground to vibrate up and down, causing less damage  The next one is S waves, which move very slowly, causing the ground to sway back and forth, left and right, which is destructive Great  Early warning systems measure the effects of P waves along the ground to predict the effects of S waves, and then issue warnings  However, scientists working on such systems have discovered that in fact, people don't have much time for them
According to the records of major earthquakes over the years, most of the strong earthquakes occur instantaneously at night, and it is impossible to organize effective defensive operations in a short period of time
 Be prepared for an earthquake