Earthquakes
Terms
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- epicenter
- the point on the surface of the earth directly above the focus
- seismograph
- device that records ground movements caused by seismic waves as they move through the earth
- aftershock
- an earthquake that occurs after a larger onein the same area; hours days or months later
- plateau
- large area of flat land elevated high above sea level
- P wave
- 1st waves to arrive at earth's surface; fastest waves; press and expand ground; can travel through solids and liquids; primary waves
- L wave
- product of P and S waves when they reach the surface; most destructive; roll like ocean waves;
- base- isolated building
- reduces amount of energy that reaches a building during an earthquake; rest on rubber pads or springs; prevents violent shaking
- Mercalli Scale
- rates the level of damage/intensity of an earthquake using the ground movements;
- earthquake
- shaking and trembeling that results from the movement of rock beneath earth's surface;
- Richter scale
- rates the earthquake's magnitude by the size of the seismic waves; good for small earthquakes
- hanging wall
- the block above a normal fault; moves downwards
- liquefaction
- process by which an earthquakes violent movement suddenly turns loose soil into liquid mud; often where soil is moist; buildings sink and pull apart
- tsunami
- the water displaced by an eq causes may form a large wave called an ___; spreads from epicenter; wave get bigger as it approaches shallower water
- stress
- force that acts on rock to change its shape or volume; 3 kinds; occur slowly in crust because of shifting of plates
- S wave
- 2nd waves of an earthquake; vibrate side to side, up and down; can't move through liquids; secondary waves
- normal fault
- when tension in the earht's crust pulls the rock apart; at an angle;hanging wall moves down when plates diverge
- reverse fault
- compression build up in the crust; same structure a normal faults but the wall move in the opposite direction
- focus
- area beneath earth's surface where rocks under stress break making an earthquake
- compression
- stress that pushes the rock until if folds or breaks' when 1 plate pushes against another; like a giant trash compressor
- syncline
- fold bending down in rock to form a valley
- anticline
- fold in rock that bends upward into an arch
- moment magnitude scale
- estimates the amount of energy released during an earthquake; good for all sized earthquakes; use fault areas and seismographs
- friction
- force that opposes the motion of one surface as it maves across another surface; exists because surfaces aren't perfetly smooth
- footwall
- block below; moves upwards
- magnitude
- a # geologists assign to an earhtquake based on it's size using seismic waves
- shearing
- stress that pushes masses of rocks in the opposite directions
- tension
- stress force that pulls the rock so the middle becomes thinner; happens when 2 plates move apart ( divergent boundry)