# Earthquakes in

```IN CLASS EXERCISE: EARTHQUAKES AND SEISMIC WAVES
NAME: __________________________
1. What is the difference between hypocenter and epicenter?
One is on the surface of the Earth and the other is at Depth. Hypocenter=Location
at depth where an earthquake initiates
Epicenter=Location on the surface of the Earth directly above the hypocenter.
2. Why are convergent margins more dangerous than transform or divergent margins?
Because subducting plates stay cool even at great depths, the lithosphere is very think
creating a very large potential rupture area. Other plate boundaries have a MUCH
smaller potential rupture area due to a thinner lithosphere.
3. How many seismographs do you need to make an accurate estimate of the epicentral location of an
earthquake? Why?
Three stations are needed to triangulate the epicenter location. Where the distance of
the three stations all agree is the epicenter location.
4. What measurement do you make off of a seismograph to calculate the distance of the seismometer to the
earthquake epicenter? Why does this work?
A seismograph measures the ground motions from the arrivals of earthquake waves.
Because p-waves and s-waves travel at different speeds, the difference in arrival
times of the p-waves and s-waves tells how far away the earthquake epicenter was.
5. Given the seismic ray pictured to the right, which path will the ray take after it
enters the lower layer?
The seismic ray will refract and travel along path A. This is
because the lower layer has a slower seismic velocity and
when a ray enters a slower layer, it bends away from the
interface between the two layers.
```