EARTHQUAKES Definition 1 a shaking or vibration of

EARTHQUAKES • Definition 1. a shaking or vibration of the ground

• Why? 1. breakage of the ground along a fault 2. elastic rebound theory

Anatomy of an earthquake 1. focus 2. epicenter 3. slip 4. seismic waves

Seismic Waves 1. measure with a seismograph

Seismic Waves 2. Types i. ii. body waves (1) P-waves (2) S-waves surface waves

Locating an earthquake

Earthquake magnitudes 1. Richter Scale i. logarithmic scale ii. the amount of energy released by an earthquake increases about 30 times for every increment

Earthquake magnitudes Mercalli Intensity Scale i. indicates destructiveness of an earthquake

Earthquakes and Plate Tectonics 1. shallow focus = divergent boundaries 2. deep focus = convergent

Earthquake Damage 1. 800, 000 earthquakes per year 2. 100 magnitude 6 - 7 3. about every 5 years there is an earthquake of magnitude > 8 4. soils saturated with water behave like fluid i. gas lines and power lines break

Forecasting Earthquakes 1. seismic gaps and recurrence studies i. San Andreas fault moves every 100 - 150 years (last great earthquake in 1857, so when is the next one due? )

Forecasting Earthquakes 2. precursor studies i. accelerated land uplift ii. increased emissions of radon from wells iii. groundwater levels rise iv. animal behavior