Earthquakes Flashcards
earthquake
a movement or trembling of the ground that is caused by a sudden release of energy when rocks along a fault move
elastic rebound
the sudden return of elastically deformed rock to its undeformed shape
focus
the location within the Earth along a fault at which the first motion of an earthquake occurs.
epicenter
the point on Earth’s surface directly above an earthquake’s starting point or focus
shadow zone
an area on Earth’s surface where no direct seismic waves from a particular earthquake can be detected
fault zone
a region of numerous, closely spaced faults
intensity
in Earth science, the amount of damage caused by an Earthquake
tsnuami
a giant ocean wave that forms after a volcanic eruption, submarine earthquake, or landslide
strike slip fault
a fault along which blocks on opposite sides of the fault plane slide horizontally past one another in opposite directions
normal fault
caused by extensional stress when rocks move away from each other
reverse fault
caused by compressional stress when plates move toward each other
thrust fault
a type of reverse fault with a fault plane that dips less than 45
extension
occurs when rock bodies are pulled apart by external forces directed away from one another
compression
occurs when rocks are squeezed by external forces directed toward one another to put stress on the rock, acting to decrease its volume or shorten its dimensions
hanging wall
the block of rock that moves upward along a fault; found above the footwall
foot wall
the block of rock that moves downward along a fault, found below the hanging wall
stress
force that acts on rocks to cause deformation by extension, compression, or shear
strain
deformation of a geologic structure caused by stress
shear
the component of stress that acts parallel to a material cross section.
magnitude
a measure of the “size,” or amplitude, of the seismic waves generated by an earthquake source and recorded by seismographs.
