VOCAB GHC Ch 3: Earthquake Geology and Seismology Flashcards
acceleration
(1) To cause to move faster. (2) The rate of change of motion.
aftershock
A smaller earthquake following a mainshock on the same section of a fault. Aftershocks can continue for years following a large mainshock.
amplitude
The maximum displacement or height of a wave crest or depth of a trough.
base isolation
Protecting buildings from earthquakes ny isolating the base of the building form the shaking ground via rollers, shock absorbers, etc.
body waves
Seismic wave that travels through the body of the earth– for example, primary and secondary waves.
compression
A state of stress that causes a pushing together or contraction.
cross-section
A two-dimensional drawing showing features in the vertical plane, as in a canyon wall or road cut.
dip
The angle of inclination measured in degrees from the horizontal.
dip-slip fault
Fault where most of the movement is either up or down in response to pushing or pulling.
fault
A fracture or belt of fractures where the two sides move past each other.
footwall
The underlying side or block of a fault.
foreshock
A smaller earthquake that precedes a mainshock on the same section of a fault.
facture
A general term for any breaks in rock. Fractures include faults, joints, and cracks.
frequency
Number of events in a given time interval. For earthquakes, it is the number of cycles of seismic waves that pass in a second; frequency = 1/period.
friction
The resistance to motion of two bodies in contact.
granite
A quartz-rich plutonic rock.
hangingwall
The overlying side or block of a fault.
hertz (Hz)
One hertz equals one cycle per second.
hypocenter
The initial portion of a fault that moved to generate an earthquake.Hypocenters are below the ground surface; epicenters are above them on the surface.
inertia
The property of matter by which it will remain at rest unless acted on by an external force.
joint
A fracture or parting in rock.
law of original continutiy
A water-laid sediment body continues laterally in all directions until it thins out do to nondeposition or butts against the edge of the basin of deposition.
law of original horizontality
Sediments are deposited in nearly horizontal layers.
law of superposition
In a sequence of sedimentary rock layers, the oldest layer is at the base, and ages are progressively younger to the top.
left-lateral fault
A strike-slip fault where most of the displacement is toward the left hand of a person straddling the fault.
magnitude
An assessment of the size of an an event.
mainshock
The largest earthquake in a sequence.
map
A two-dimensional representation showing the features in a near-horizontal surface, such as the ground.
normal fault
A dip-slip fault in which the upper fault block has moved downward in response to tensional stress.
period
The length of time for a complete cycle of seismic waves to pass; equals 1/frequency.
permeability
The capacity of a porous material to transmit fluids.
primary (P) wave
The first seismic wave to reach a seismometer. Movement is by alternating
resonance
The act of resounding, ringing.
retrofit
Reinforcement or strengthening of an existing building or other structure.
reverse fault
A dip-slip fault where the upper fault block has moved upward in response to compressional stresses.
right-lateral fault
A strike-slip fault where most of the displacement is toward the right hand of a person straddling the fault.
secondary (S) wave
Second seismic wave to arrive at the seismometer. S waves move only through solid bodies.
seism
Earthquake
seismic moment
A measure of earthquake size that involves amount of movement on the fault, the shear strength of the rocks, and the area of fault rupture.
seismic wave
A general term for all waves generated by earthquakes.
seismogram
The record made by a seismograph.
seismograph
An instrument that records vibrations of the Earth.
seismology
The study of seismic waves generated by earthquakes.
seismometer
An instrument that detects Earth motions.
shear
The failure of a body where the mass on one side slides past the portion on the other side.
stress
External forces acting on masses or along surfaces; forces include shear, tension, and compression.
strike
The compass bearing of the trend of a rock layer as viewed in the horizontal plane.
strike-slip fault
Fault where most of the movement is horizontal or slide-past in character.
surface waves
A class of seismic waves that travel along the surface only– for example, Love and Rayleigh waves.
tension
A state of stress that tends to pull a body apart.
transform fault
A strike-slip fault that connects the ends of two offset segments of plate edges, such as spreading centers or subduction zones.
wavelength
The distance between two successive wave peaks, or troughs, in seismic waves or ocean waves.
