Earthquakes Chapter 19

San Francisco https://www.youtube.com/watch?v=Z7eABGpOHv8

Focus vs. Epicenter Focus Epicenter _________– where the rock breaks and seismic waves begin; can be at deep or shallow depths _________ – point on the surface directly above the focus; usually what is used to locate the position of an earthquake Epicenter

Seismic Waves Primary Secondary Surface _______ (P) Wave – fastest, able to travel through liquids, energy travels in the same direction wave is traveling ________ (S) Wave – slower, not able to travel through liquids, energy travels at right angles to direction wave is traveling ________ (L) Wave – travels along the surface, knocks down and destabilized structures. Secondary Surface

The interior structure of the earth is determined by the pattern of seismic waves. The __________ is liquid so s-waves can not pass through. outer core

The difference in arrival times between p-waves and s-waves is called __________. lag time The greater the lag time (shown here as the distance between the two curves) the _________ the distance away from the earthquake. greater

To locate the epicenter of an earthquake, a minimum of ____ seismograph stations is needed. The location is where all circles _______. three intersect

How do we measure earthquakes Earthquakes are measured on 2 scales Richter Scale measures _magnitudes Modified Mercalli Scale measures damage