What is an Earthquake? Movement of the ground that occurs when rock inside the Earth pass their elastic limit, break suddenly, and experience elastic rebound.

EARTHQUAKES Elastic Limit: the ability of rocks to bend to a certain point. Elastic Rebound: Rocks become strained, break, and snap back-rebound back to shape.

EARTHQUAKES Folding: Bending of a rock. Faulting: Breaking of a rock

How an Earthquake happens? 1.Rocks become strained or stressed 2.Rocks build up potential energy 3.Energy is released- vibrations move through the earth. 4.Rocks return to normal position with no stress/strain

The Focus and Epicenter of an Earthquake Focus: The point within Earth where faulting begins is the focus, or hypocenter Epicenter: The point directly above the focus on the surface is the epicenter

EARTHQUAKES Seismic waves- energy waves released during an earthquake. Different Types –Primary –Secondary –Surface

Primary Waves –a.k.a. = P waves –Fastest wave –First to arrive on a seismograph –Move back and forth

Secondary Waves –a.k.a = S waves –Secondary waves –Second to arrive on a seismograph –Move side to side

Surface Waves –a.k.a = L waves –Slowest waves –Largest waves –Cause most destruction –Move side to side or a swaying motion & backward rolling motion

EARTHQUAKES Seismograph- Instrument used to detect seismic waves/vibrations released during an earthquake. Seismogram- paper/record of seismic waves.

EARTHQUAKES Richter Scale- Magnitude is based on measurements of amplitudes or heights, of seismic waves as recorded on seismogram. Magnitude - the height of the lines traced on a seismogram is a measure of the energy released by the earthquake.

TSUNAMIS Seismic sea wave Powerful seismic sea wave that begins over an ocean-floor earthquake.

TSUNAMIS