Unit 3: The Dynamic Earth EarthQuakes! Unit 3: The Dynamic Earth

What is an earthquake? Shaking of the earth’s crust due to a release of energy/pressure along a fault line Fault: crack in the earth’s crust where there is movement

What do earthquakes result from? Movement along a plate boundary Volcanic eruptions Plate: section of the earth’s crust or lithosphere which moves-includes oceanic and continental crust (either, or both)

Elastic rebound theory Explains movement Says: strain builds up between 2 sections of crust, deforms them. When the stress overcomes friction, crust shifts and goes back to its original shape ( in new place).

Earthquake Anatomy Seismic waves: how energy travels through the Earth from the EQ Focus: point of origin Of EQ underground Earthquake Anatomy Epicenter: where the EQ Originates on the surface focus

How do we measure Earthquake strength or magnitude? Richter Scale- based on powers of ten (log scale), calculated from amplitude of highest S-Wave on seismogram Measures from 1-10 1=1 2=10x more powerful 3=100x more powerful How powerful would a magnitude 5 earthquake be then a magnitude 1? Then a 4? Answer: 10,000 and 10x

How do we measure Earthquake Intensity? Modified Mercalli Scale- based upon peoples observations, ranges from 1-12

Seismic Waves: Three types: P,S,L P wave: primary, compress ional, body wave, travels through solid, liquids, and gases S-Wave: Secondary, Shear, Transverse, body wave, travels through Solids only L-wave: Longitudinal, surface wave, (p/s wave converts to this when reaches the surface), two types-Love and Rayleigh Wave

Diagram of Body Waves:

Diagram of a Surface Wave: