Earthquakes

# Earthquakes

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## Earthquakes

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##### Presentation Transcript

1. Earthquakes Chapter 7

2. Web Sites about Earthquakes • www.iris.edu • http://earthquake.usgs.gov/ For Fun • http://earthquake.usgs.gov/learn/facts.php

3. Information We Need from Earthquakes (EQ) • EPICENTER (Latitude, Longitude) • FOCUS ( Hypocenter ) (Depth of the EQ) • How Big it was ? How much Energy? (Mercalli intensity vs Richter Magnitude) • What Kind it was? What type of Fault • How Long it was ?

4. Epicenter vs. Hypocenter (Focus)

5. Mercalli Intensity Scale vsRichter Magnitude • Mercalli Intensity is measured by means of the degree of damage to structures of human origin Based on (IsoseismalLines) Richter Magnitude (Inhabited and Uninhabited regions) • Seismic wave amplitudes measured by a seismograph • He replace numbers by their logarithms. so instead of using their amplitudes used the powers of the numbers

6. Mercalli vs Richter Mercalli Richter Magnitude When a logarithmic scale every time the magnitude goes up by 1 unit, the amplitude of the earthquake waves is increased by 10 times Example 4 to 5 ( 10 times ) 4 to 6 (100 times) 4 to 7 (1000 times) • Map of intensities with isoseismal lines

7. 2010 Chile EQ vs Haiti EQ Chile Earthquake Magnitude scale • www.usgs.gov

8. Earthquakes Waves • Body Waves (P waves and S Waves) • Surface Waves ( Rayleigh and Love Waves) P-S Waves 3 Components seismograph

9. Locating and Earthquake • We need at least 3 station to estimate the epicenter of an earthquake ! • What do seismologist need arrival times for P and S waves A simple formula is (S time – P time )x 8.2 = Distance in KM (Kilometers)

10. Example

11. Earthquakes in Plate Boundaries • Transform California USGS today • Convergent Example Chile Earthquake (Nazca Plate subducting in South-America Plate) • Divergent USGS website eq today