What i learned today was Wave speed helps determine distance.

     What i   learned today was  that the farther a station is from the spicenter, the longer it takes for waves to reach the station and the farther apart P and S waves become. Large enough earthquakes carry energy from one side of the earth to the other.  There are more than 4000 seismograph stations. Only certain waves reach certain places. S waves only move through solids. All waves change speed in different materials. Earthquakes that occur frequently are generally weaker. Damage depends on Distance from epicenter, geology, and construction, and population. Areas near an earthquake spicenter are generally shaken more, resulting in more damage.