Unit 7 - Earthquakes Flashcards
(21 cards)
What is an earthquake?
The sudden shaking of the ground caused by movement in the Earth’s Crust.
What causes earthquakes?
Stress and Strain
What are the three kinds of stress?
Compression; Tension; Shear
What is strain?
The deformation of materials in response to stress.
What is stress?
The total force acting on crustal rocks per unit of area.
What is elastic deformation?
When a material is compressed, bent or stretched.
What is plastic deformation?
When stress passes the elastic limit, causing permanent deformation even after stress is released.
What is a fault?
Any fracture or system of fractures along which the Earth moves.
What are the three types of faults?
Normal; Reverse; Strike - Slip
What are seismic waves?
Vibrations in the ground produced by Earthquakes.
What are the three types of of seismic waves?
Primary; Secondary; Surface
What is a primary wave?
Squeeze and push rocks in the direction along which the waves are traveling.
What is a secondary wave?
Slower than P waves. Move like a jump rope jerked up and down at one end. Also called body waves.
What is a surface wave?
Travel only along the surface, causing ground to move.
What is the focus of a seismic wave?
The point of failure where waves originate. Usually kilometers below the surface. Can be shallow, mid or deep focus depending on depth. Shallow earthquakes cause the most damage.
What is the epicenter of a seismic wave?
The point on Earth’s surface directly above the focus.
What are the two machines used to measure seismic waves?
Seismometers and Seismographs
What did seismic waves give us?
A mapping of of the Earth’s interior?
What is the main scale for rating earthquakes?
Richter Scale
What is occurs when areas with sand nearly saturated with water and seismic vibrations?
Soil Liquefication
What is a tsunami?
A large ocean wave generated by vertical motions of the seafloor during an earthquake.
