Instruments That Monitor Faults (pages 180–181)

Key Concept: To monitor faults, geologists have developed instruments to measure changes in elevation, tilting of the land surface, and ground movements along faults.

Ground movements near a fault are a clue that an earthquake might happen. So scientists measure ground movements near faults. They use tiltmeters, creep meters, and GPS satellites.

Tiltmeters show how much the ground is tilting, or tipping. A tiltmeter works like a carpenter’s level. When the ground tilts, water inside a glass bulb shows how much tilting there is.

Creep meters show how far the sides of a fault have moved in opposite directions. A creep meter uses a wire stretched across the fault. The wire gets longer when the two sides move apart.

Scientists put markers along both sides of a fault. GPS satellites detect tiny movements of the markers in any direction.

Creep meters GPS Satellites

Using Seismographic Data (pages 182–183)

Key Concept: Seismographs and fault-monitoring devices provide data used to map faults and detect changes along faults. Geologists are also trying to use these data to develop a method of predicting earthquakes.

Circle the letter of the choice that describes where big earthquakes are likely to happen. a. at faults where rocks move easily b. at faults where rocks do not move easily c. at rocks where there are no faults

true or false? Scientists can now predict exactly where and when earthquakes will happen. False

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