Monitoring
Faults
CH 5 Prentice Hall
p.168-171
Devices that Monitor Faults
• Instruments used to
observe changes.
– Measure stress and
deformation of the crust.
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Creep Meters
Laser-Ranging Devices
Tiltmeters
Satellites
Creep Meters
• A meter with a wire stretched across a fault
to measure horizontal movement.
– Wire is anchored to a post.
– The wire on the other side of the fault has a
weight attached to it.
– Movement can be determined by measuring how
much the weight has moved.
Laser-Ranging Devices
• Detects tiny fault movements with a laser.
– The device measures the time it takes for the
beam to travel to the reflector and back.
– Can detect any change in distance.
Tiltmeters
• Measures the tilting of the ground.
– Acts like a carpenters level.
• Geologists read the scales to see the amount
of tilting along a fault.
Satellites
• Satellites bounce radio waves off
the ground and the satellite
records them.
• Can detect small changes in
elevation, may result when
stress deforms the ground.
Monitoring Risk in the US
• Geologists cannot predict earthquakes.
– Exactly what will happen remains uncertain.
• Stress may build up and not release an earthquake.
• Or stress may be released in another part of the fault.
• Geologists know that earthquakes are likely
wherever plate movements store energy in
the rock along faults.
– Geologists can determine the risk by where faults
are active and other earthquakes have occurred.
Monitoring Risk in the US