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Transcript of Monitoring Faults
Helps geologists predict earthquakes.
Uses wire stretched across a fault to measure horizontal movement of the ground.
Uses a laser beam to detect even tiny fault movements.
Use radar to make images of faults.
Devices that Monitor Faults
To observe changes in faults, geologists put in place instruments that measure stress and deformation in the crust.
Instruments that geologists use to monitor these movements include creep meters, laser-ranging devices, tiltmeters, and satellites.
The only clue may be a slight rise or fall in the elevation and tilt of the land.
On one side of the fault, the wire is anchored to a post.
On the other side of the fault the wire is attached to a weight that can slide if the fault moves.
Geologists can measure the amount that the fault has moved by measuring how much the weight has moved against a measuring scale.
The device calculates any change in the time needed for the laser beam to travel to a reflector and bounce back; thus, the device can detect any change in distance to the reflector.
Measures tilting of the ground.
Consists of two bulbs that are filled with a liquid and connected by a hollow stem.
If the land rises or falls even slightly, the liquid will flow from one bulb to the other.
Each bulb has a measurement system .
The satellite bounces radio waves off the ground, and as the waves echo back into space the satellite records them.
The time it takes for the radio waves to make their round trip provides precise measurements of the distance to the ground.
Helps geologists detect small changes in elevation.
Monitoring Risk in the United States
Geologists can determine earthquake risk by locating where faults are acting and where past earthquakes have occurred.