To locate the quake focus:
• Need a minimum of 3 seismometer stations
Where do earthquakes occur?
• At what depth?
o Less than 700 km
o 90% are less than 100 km deep
o Note: radius of earth is 6370 km
Why do earthquakes only occur in the outer 10% of the earth?
• Only the outer part of the earth is rigid enough (ie.
Sufficiently ELASTIC) to experience BRITTLE FAILURE (fault
• Deeper on the earth it is to PLASTIC (or liquid?)
How do we estimate energy released from a Quake?
• 1. “Measure” the Intensity
o based on observed damage (eg. The Mercalli Scale)
o Varies with distance from epicenter
• 2. Measure the Richter Magnitude
o a quantitative measure of energy released
determined from the maximum s-wave amplitude