Transcript Monitoring Earthquakes - Hicksville Public Schools / Homepage

AIM: How are earthquakes monitored?
OBJ: Given notes and activity sheet SWBAT explain how a
seismograph works, how fault activity is monitored and how
seismographic data is used with 70% accuracy
DN: Watch video: https://www.youtube.com/watch?v=kXrftpP-bRY
HW Check- Earthquakes & Seismic Waves
ACT: Introduction to seismograph, monitoring faults, and
using seismographic data.
Text, read, p. 60-65, Work on Monitoring Earthquakes
HW: Complete Monitoring Earthquakes Activity Sheets;
Work on Tectonics Activity Sheets, Tectonics Exam, Friday,
February 13.
Seismograph: instrument used to measure
seismic waves (earthquake movement/vibrations)
Seismic waves cause the seismograph’s drum to
vibrate.The suspended weight with the pen remains
stationary while the drum records the vibrations. The
pen remaining stationary occurs due to a basic
principle of physics, “every object resists any change to
its motion”.
Seismogram: a record of an earthquake’s
seismic waves. The height of the jagged line
represents the magnitude (strength) of the earthquake.
Seismograph & Seismogram
Instruments that Monitor Faults:
Change in elevation and tilt of the land is related to the
build up of stress in the rocks. Increasing stress
eventually results in an earthquake. To monitor fault
activity, a variety of devices are used:
Tiltmeter: measures vertical movement (tilting or
raising of the ground); ex: carpenter’s level
Creep Meter: measures horizontal movement of the
ground across a fault.
Laser Ranging Devices: measures long distance
horizontal movement.
GPS Satellites: monitor changes in elevation, tilt of the
land and horizontal movements along a fault with great
precision.
Tilt Meter
Creep Meter
Using Seismographic Data:
Seismogram and fault monitoring data are used to map
active faults, monitor changes along faults and develop
a method of predicting earthquakes.
Mapping Faults: faults can be hidden by a thick layer
of rock or soil. Seismic data helps to map fault length
and depth so that the earthquake risk for an area can
be determined.
Monitoring Changes Along Faults:
Friction: is the force that opposes the motion of one
surface as it moves across another surface. If friction is
low, the stress is low and a major earthquake is
unlikely. If the friction is high, the rocks lock together,
the stress increases until an earthquake occurs.
3D Fault Model
Predicting Earthquakes:
Geologist’s can not predict when and where an
earthquake will strike.
Usually, stress increases along a fault until an
earthquake occurs. But sometimes the
earthquake doesn’t occur or one or more
quakes occur along subsidiary parts of the fault.
Predicting an earthquake remains an uncertain
science.