Chapter 2: Earthquakes
S waves
seismic waves that vibrate from side to side as well as up and down. This one is very destructive
3 steps to protect urself from eq's
DROP,COVER,HOLD
Geologists can determine eq risk by locating where ___ are active and where ___ eq's have occured
Faults, Past
Seismic waves carry energy from an earthquake away from the ____, through the Earth's ___, and across the surface
Focus, interior
Reverse Fault
Same structure as a normal fault but moves in opposite direction. Compression causes this to form
Over millions of years, the force of plate movement can change a flat plain into landforms such as anticlines,____, folded mtns,___-____, and plateaus
Synclines, Fault-block mtns
GPS satellites
Used to locate great points on Earth's surface with precision
Laser-Ranging Devices
Uses a laser beam to detect horizontal fault movments
Creep Meters
Uses a wire stretched across a fault to measure horizontal movement of the ground
Syncline
A fold in a rock that bends down to form a valley
Anticline
A fold in rock that bends upward into an arch
Stress
A force that acts on rock to change its shape or volume
Plateau
A large area of flat land elevated high above sea level. Some form when forces in Earth's crust push up large, flat block of rock
Magnitude
A number that geologists assign to an earthquake based on eq's size
Richter Scale
A rating of an eq's magnitude based on the size of the eq's seismic waves
Moment Magnitude Scale
A rating system that estimates the total energy released by an eq.
Aftershock
An eq that occurs after a larger eq in the same area
Seismograph
An instrument that records and measures seismic waves
Base isolate building
Designed to reduce the amount of energy that reaches the building during an eq and rests on springs or shocking absorbing rubber pads
Mercalli Scale
Developed to rate eq's according to their level of damage at a given place
Tiltmeters
Measures tilting or raising of the ground
Surface waves
Move more slowly than P and S waves, but produce severe ground movements
Most faults occur along plate boundaries, where the forces of plate motion push or pull the crust so much. There are three main types of faults:_____,______,______
Normal, Strike-Slip, and Reverse Faults
Liquefaction
Occurs when an eq's violent shaking suddenly turns loose, soft soil into liquid mud, create cracks
Tension
Pulls on crust, stretching rock so it becomes thinner in the middle
Geologists use ___ ___ to locate an eq's epicenter
Seismic waves
P waves
Seismic waves that compress and expand the ground like an accordion, a lot faster
Fact:
Seismographs and fault-monitoring devices provide data used to map faults and detect changes along faults.
Causes of eq damage???
Shaking, Liquefaction, Aftershocks, and Tsunamis
Compression
Squeezes rock until it folds or breaks
Shearing
Stress that pushes a mass of rock in two opposite directions
Normal Faults
Tension in Earth's crust pulls rock apart, causing this. There is a top block and a bottom block
_____,shearing, and compression work over millions of years ago to change the shape and ___ of rock.
Tension, volume
Focus
The area beneath Earth's surface where rock that is under stress breaks, triggering an earthquake
Hanging wall
The block of rock that lies above
Footwall
The block of rock that lies below
Friction
The force that opposes the motion of one surface as it moves across another surface
Seismogram
The pattern of lines/the record of an eq's seismic waves produced by a seismograph
Epicenter
The point on the surface directly above the focus
Strike-slip Fault
The rocks on either side slip past each other sideways, with little up or down motion. Shearing creates this fault
Earthquake
The shaking and trembling that results from the rock movment of rock beneath Earth's surface
Tsunami
The water displaced by the eq may form a large wave
Geologists have developed instruments to measure changes in elevation, ____ of the land surface, and ground _____ along faults
Tilting, movements