Earthquakes

Earthquakes are more than shaking of the earth… Seismology is the study of earthquakes. Seismologist: An individual who studies Earthquakes

Where do earthquakes occur? A fault: a break in the Earth’s crust along which blocks of crust slide relative to one another. Earthquakes occur along faults because of this sliding.

What Causes Earthquakes? Stress increases along faults near tectonic plate boundaries, causing rocks to deform. Deformation – the change in the shape of rock due to stress.

Deformation Types of Deformation: Plastic Deformation – like a piece of molded clay. Does not cause Earthquakes. Elastic Deformation – Rock stretches farther than steel can, but rock will break at some point. Like a rubberband snapping. Does cause Earthquakes.

Elastic Rebound The sudden return of elastically deformed rock to its undeformed shape. Elastic Rebound occurs when more stress is applied to the rock than it can withstand. During elastic rebound, energy is released and travels as seismic waves, which can cause an earthquake.

Faults at Plate Boundaries Plate Boundary Motion Major Fault Type Transform Strike-slip Fault Convergent Reverse Fault Divergent Normal Fault

Earthquake Zones Places where a large number of faults are located – such as the San Andreas fault Zone in California. Not all faults are located at tectonic plates boundaries, sometimes earthquakes occur at fault lines in the middle of a tectonic plate.

How do Earthquakes Travel? Waves of energy travel through the Earth are called Seismic Waves. Body Waves – seismic waves that travel through the Earth’s interior. Surface Waves – seismic waves that travel through the Earth’s surface.

Wave Types L Waves (surface) - Arrives last and is MOST destructive P Waves (primary) – travel through solids, liquids and gases. (fastest wave type) Compress and release S Waves (secondary) – cannot travel through liquid (second fastest wave type) Up and Down...like an “S” L Waves (surface) - Arrives last and is MOST destructive Moves up and down.