eas 220 lab 3: earthquakes. travel time graph
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EAS 220 Lab 3: EARTHQUAKES
Travel Time Graph
Plate Boundaries
Types of BoundariesDivergent
Convergent
Transform
Divergent Boundaries: Spreading zones (ex. Mid Atlantic Ridge, Red Sea Rift)
Convergent: Subduction (ex. West coast of South America, Aleutian Islands)
Transform Boundaries: Plates slide past each other (ex. San Andreas in
California)
Richter Magnitudes Description Earthquake Effects Frequency of Occurrence
Less than 2.0 Micro Microearthquakes, not felt. About 8,000 per day
2.0-2.9 Minor Generally not felt, but recorded. About 1,000 per day
3.0-3.9 Minor Often felt, but rarely causes damage.
49,000 per year (est.)
4.0-4.9 Light Noticeable shaking of indoor
items, rattling noises. Significant damage unlikely.
6,200 per year (est.)
5.0-5.9 Moderate
Can cause major damage to poorly constructed buildings over small regions. At most
slight damage to well-designed buildings.
800 per year
6.0-6.9 Strong Can be destructive in areas up to about 100 miles across in
populated areas. 120 per year
7.0-7.9 Major Can cause serious damage over larger areas. 18 per year
8.0-8.9 Great Can cause serious damage in areas several hundred miles
across. 1 per year
9.0-9.9 Great Devastating in areas several thousand miles across. 1 per 20 years
10.0+ Great Never recorded; see below for
equivalent seismic energy yield.
Extremely rare (Unknown)
Earthquake FactsLargest ever recorded: 9.6 in Chile in 1960
2nd largest: (Largest US Earthquake): Alaska 1964 Good Friday Earthquake, Magnitude 9.4
3rd largest: Indian Ocean 2004. Indonesia/Sumatra. Generated tsunami (9.2-9.3)
*3 big earthquakes: 1811, 1812 (within two months!)
*made Mississippi flow backwards
*Rang church bells in Boston and felt widespread. Probably close to 7.8 magnitude.
New Madrid Fault Zone
Biggest NY EarthquakesUtica, Attica, Syracuse have had quakes.
Massena 1940’s: magnitude 6. Blue Mountains: active area, magnitude 5.5 a few years ago.
Historically, large earthquakes in NYC area. Frequent magnitude 2-3. Beneath city itself, historically 6’s. Magnitude 5.1, 2002.