What are Earthquakes?
- P waves are the first waves to be recorded by a Seismograph, followed by the S waves and then surface waves.
- The further the Seismograph is from the source of the earthquakes, the longer the lag time between the P waves and S waves
- A travel – time graph shows the relationship b/w P and S wave arrival times and the distance from an earthquakes epicenter
Locating the Epicenter
- Since a Seismograph tells scientist the distance to an earthquake, it does not tell them the exact location of the earthquake
- To determine the exact location of an earthquake, we need to know the distances from at least three different stations in order to plot an epicenters location
- After getting data from three stations, draw a circle from the station, the point at which all three circles meet is the epicenter
Measuring an Earthquakes Magnitude
- The magnitude of an earthquake can also be measured using the seismogram.
- The scale of earthquake magnitude was introduced by Charles F Richter in 1935
- So each increase in a whole number in the Richter magnitude is 31 times more powerful than the last number
- ie – magnitude 7 is 31 more powerful than a magnitude 6