Stress and Strain
What is compression
The type of stress that causes a material to shorten.
What is a fault
A fracture or system of fractures along which Earth moves.
What are p-waves
Primary waves that squeeze and push rocks in the direction the waves are traveling.
What is the Richter scale?
A numerical rating system that measures the magnitude of an earthquake based on the amplitude of the largest seismic wave.
What is pancaking?
Structural failure where shaking causes a building's supporting walls to collapse and upper floors fall one on top of the other.
What is elastic deformation
Deformation caused under low stress conditions where a material returns to its original shape once stress is removed.
What is a normal fault
A fault where movement is partly horizontal and partly vertical, with rock on one side moving down relative to the other side, stretching the crust.
What are s-waves
Secondary waves that are slower than P-waves and cause rocks to move perpendicular to the direction of the waves.
What is magnitude
The measure of energy released during an earthquake.
What is soil liquefaction?
A phenomenon where seismic vibrations cause sandy, water-saturated ground to behave like a liquid.
What is strain
The deformation of materials in response to stress.
What is reverse fault
A fault formed by horizontal and vertical compression that pushes rock on one side up relative to the other side.
What are surface waves
The third and slowest type of seismic waves that travel only along Earth's surface.
What is the moment magnitude scale?
A rating scale that measures earthquake energy by taking into account the size of fault rupture, amount of movement, and rock stiffness.
What is a tsunami?
A large ocean wave generated by vertical motions of the seafloor during an earthquake.
What is plastic deformation
Permanent deformation that occurs when stress builds up past the elastic limit.
What is a strike slip fault
A fault caused by horizontal shear where movement is mainly horizontal and in opposite directions.
What is the focus on an earthquake
The point of initial fault rupture, usually several kilometers below Earth's surface.
What is the modified Mercalli scale?
A scale from I to XII used to measure earthquake intensity based on damage caused.
What is seismic gap?
Sections along active faults that have not experienced significant earthquakes for a long period of time.
What is elastic limit?
The point past which rocks undergo plastic deformation instead of elastic deformation.
What causes faults to form?
Forces acting on rock that exceed the rock's strength
What is the epicenter
The point on Earth's surface directly above the focus of an earthquake.
Why are at least three seismic stations needed to located an epicenter?
Scientists draw circles from each station using the distance to the epicenter; the point where all three circles intersect is the epicenter location
What factors determine earthquake damage severity?
Structural failure, land and soil failure, tsunami generation, building resonance frequency, and ground material type.