Earthquakes Flashcards
Define fault scarp
A small step on the ground surface where one side of a fault has moved vertically with respect to the other
Define fault line
The ground surface exposure of a fault
Define a strike
Compass orientation of the line of intersection between the plane of interest and the Earth’s surface
Define a dip
The angle the plane makes with the horizontal surface; it measures steepness
What is a Normal fault
A dip-slip fault where the hanging wall moves down relative to the footwall
What is a reverse fault?
A dip-slip fault where the hanging wall moves up relative to the footwall
What is a thrust fault?
Has the same sense of a slip as a reverse fault, but the fault is at a much gentler angle
What is a strike-slip fault?
A near vertical fracture on which slip occurs parallel to the strike (no up or down motion takes place on these faults)
What is displacement?
The amount of movement across a fault
Define stress
The force applied to an object
Define compressive stress
Normal stress where rock is being pushed
Define tensile stress
Normal stress where rock is being pulled
Define shear stress
Shear moves one part of a material sideways relative to another part
Define strain
Deformation (change in shape) resulting from stress
Define stick
Friction prevents motion
Define slip
Friction is briefly overwhelmed by motion
What is elastic deformation?
The object will return to its original shape after the stress is removed (aka the shape is recoverable)
What is the elastic rebound theory?
When rocks on either side of a fault are subjected to stress, rocks accumulate strain until internal strength is reached, then break and energy is released as an earthquake
Define hypocenter
The place where fault slip initiates
Define epicenter
Land surface right above the hypocenter
What is a body wave?
Pass through Earth’s interior
What is a p-wave?
The fastest waves, compressional. Cause particles of the material to move back and forth parallel to the direction of wave movemebt
What are s-waves?
Secondary waves, slower than p-waves. Shear waves, material will move back and forth perpendicular to the direction of wave movement
