Terms Flashcards
Accelerometer
Sensors that measure changes in speed, such as the shakes produced by earthquakes
Seismometer
An instrument that measures earth waves
Earthquake
A series of low-frequency shock waves traveling through the earth
Stress
A measure of force exerted within an object
Compression
A force being pressed down onto an object
Tension
Taking slack out of a flexible object-as in pulling on a rope in tug-of-war.
Shear
Exists when forces are acting in opposite directions on different parts of the same object
Divergent Boundaries
The plate sections of the earth that move apart
Convergent Boundaries
The plates that move toward each other
Transform Boundaries
Places where plates slide past each other in opposite directions along long cracks in the crust.
Strain
The distortion, bending, stretching, or compression of a material under stress.
Joints
Cracks in rocks
Fault
Occurs when the sections of rock on opposite sides of the crack move relative to each other
Fault Plane
The smooth surface between two pieces of a broken rock
Strike
The direction of a fault
Dip
The angle of the fault face downward from the horizontal
Normal Fault
When the block above the faults surface drops in relation to the block under the fault
Reverse Fault
Upper block rises in relation to lower block
Dip-Slip Fault
A fault’s motion that is parallel to its dip (up and down).
Strike-Slip Fault
Strike-Slip Fault
Lubricants
Oil, grease, and other substances used to reduce friction
Locked Fault
Builds up shear stresses, as the adjacent plates continue to move slowly
Aftershock
Secondary earthquakes
S Waves
The second type of waves to arrive at a seismic station
P Waves
The fastest body waves
Body Waves
waves that pass right through the earth
Focus
center of earthquake - underground
Epicenter
A spot of the earth’s surface directly above the focus
Richter Scale
A scale that measures the strengths of earthquakes
Magnitude
Indicates the energy released by the earth movement
Intensity
A measure of how much damage that actually results from the earthquake
Modified Mercalli Intensity (MMI)
The earthquake destructiveness scale
Two types of surface waves
love and rayleigh waves
amount of energy change with each level on the Richter scale
31.6
Analogous day theory
a symbolic day where any period of time on Earth could pass for one “workday” and not a literal 24 hours
