Seismometers
- A seismometer is the detecting and recording parts of a larger apparatus known as seismograph. Seismometers are pendulum type devices mounted on the ground that measure the displacement of the ground with respect to a stationary reference point.
- Since a seismometer records the motion in only one orthogonal direction, three seismometers are needed to record all components of ground motion.
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| Vertical Component Seismometer |
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| Horizontal Component Seismometer |
Creep meter
Creep meter measures minute gradual movement along a fault. In the past, such meters used to use wire stretched across a fault. Current creep meters use laser technology.
Creep meter measures minute gradual movement along a fault. In the past, such meters used to use wire stretched across a fault. Current creep meters use laser technology.
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| Creep Meter |
Gravimeter
Gravimeter measures the variations in the local force of gravity. Such variations are the result of changes in underground rock density.
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| Gravimeter |
Laser can measure the round-trip travel time of a light beam between two points. When the relative positions of the two points changes as a direct result of an earthquake, the travel time also changes.
Accelerometer
- An accelerometer (accelerograph) is a seismometer which records large accelerations, thus they are also known as strong motion seismometer.
- An accelerometer located in a building does not run continually. It is triggered by a P-wave and runs for a fixed period of time.
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| Accelerometer |
- Scintillation counters are installed in wells to measure amount of radioactive radon gas in the water. Minute amounts of radon are released into well water by rocks under stress.
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| Scintillation Counter |