Science Explorer
Terms
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- focus
- the point beneath the Earth'surface where rock that is under stress breaks, triggering an earthquake
- Surface waves
- they move more slowly that S waves and P waves, but they produce the move severe ground movements
- epicenter
- the point on the surface directly above the focus
- seismograph
- records the ground movements caused by seismic waves as the move through the Earth
- earthquake
- shaking and trembling that results from the movement of rock beneath Earth's surface
- stress
- a force that acts on rock to change its shape or volume
- magnitude
- a measurment of an earthquake strength based on seismic waves and movement along faults
- shearing
-
stress that pushes a mass of rock in two opposite directions
it can cause rock to break and slip apart or to change its shape - Mercalli scale
- developed to rate earthquakes according to their intensity
- tension (extension)
- stress that pulls on the crust, strechiong rock so that it becomes thinner in the middle
- compression
- stress that squeezes rock until it folds or breaks
- deformation
- any change in the volume or shape of Earth's crust
- fault
-
a break in Earth's crust where slabs of crust slip past each other
faults usually occur along plate boundaries,where the forces of plate motion compress,pull,or shear the crust so much that the crust breaks - Richter scale
- a rating of the size of seicsmic waves as measured by a particular type of mechanical seismograph
- strike-slip fault (shearing)
- the rocks on either side of the fault slip past each pther sideways with little or no up-or-down motion
- seismic waves
-
vibrations that travel through Earth carrying the energy released during an earthquake
they carry the energy of an earthquake away from the focus,through the Earth's interior,and across the suface - normal fault (tension)
- the fault is at an angle, so one block or rock lies above the fault (hanging wall) and one lies below (foot wall)
- What are the 3 types of seismic waves?
-
P waves
S waves
Surface waves - reverse fault (compression)
- same as normal fault but the blocks move in the opposite direction
- P waves (primary waves)
- earthquake waves that comress and expand the ground like an accordian
- moment magnitude scale
-
a rating system that estimates the total energy released by an earthquake
this scale can rate earthquakes of whatever size, near or far - fault-block mountain
- a mountain that forms where a normal fault uplifts a block of rock
- syncline
- a fold in rock that bends downward in the middle to form a bowl
- anticline
- a fold in rock that bends upward into an arch
- S waves (secondary waves)
- earthquake waves that vibrate from side to side as well as up and down
- plateau
- a large area of flat land elevated high above sea level