Earthquake Monitoring

Analog Seismometers

Analog stations are called "analog" because the analog signal is converted into digital information at the site of data processing. This means that the analog signal must be sent, in this case over phone lines, from each station to the central site. Each station's signal is then converted from analog to digital by hardware and processed by computers.

Signals from analog stations go off-scale quickly because the electronics and analog phone lines have limited dynamic range. However, each analog station is somewhat simpler, the time stamping of the data is done simultaneously, and the data conversion hardware is at the central site, so the analog stations are somewhat easier to maintain.

Big Machines

Ranger

Photo of the Ranger seismometer was developed in the late 1950/s for a hard (in excess of about 3kg or 6.6lbs) landing on the Moon. The mass weighs about 1.5 kg (about 3.3 lbs) and is actually a suspended ring magnet.

The Ranger seismometer was developed in the late 1950/s for a hard (in excess of about 3kg or 6.6lbs) landing on the Moon. The mass weighs about 1.5 kg (about 3.3 lbs) and is actually a suspended ring magnet.

Wood-Anderson

Phot of the Wood-Anderson seismometer developed in the 1920's.

Harry Wood and John Anderson developed the Wood-Anderson seismometer in the 1920's to record local earthquakes in southern California. It photographically records the horizontal motion.

Viking 75

Photo of the Viking 75 seismometerthat was first developed to be placed on the surface of mars in 1976 during the Viking Mars Mission.

This is a model of the seismometer that was first developed to be placed on the surface of mars in 1976 during the Viking Mars Mission. It records shaking in all three dimensions.


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