Earthquake Sensors

An Earthquake Alert System (EAS) could give several seconds to several tens of seconds warning before the strong motion from a large earthquake arrives. Such a system would include a large network of sensors distributed within an earthquake-prone region. The sensors closest to the epicenter of a particular earthquake would transmit data at the speed of light to a central processing center, which would broadcast an area-wide alarm in advance of the spreading elastic wave energy from the earthquake. This is possible because seismic energy travels slowly (3 to 6 km/s) compared to the speed of light (Real-time earthquake monitoring, 1991).

Utilities, public and private institutions, businesses, and the general public would benefit from an EAS. For example:

1. Facilities with high energy or high precision machinery could be shut down before strong motion arrives (e.g., power plants, power distribution centers, refineries, factories, and computer systems).

2. Airport operations could be suspended, hospitals alerted, and trains stopped.

3. Fire station doors could be opened.

4. Emergency generators could be turned on.

5. Emergency services could be deployed.

6. Audio alarms could alert people and perhaps give the extra time needed to move to a place of relative safety in the immediate area.

Although many earthquake protection systems exist that automatically shut down power, gas mains, etc. whe

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estimated by using the distance estimate and determining the P-wave angle of incidence from initial motion on the horizontal and vertical accelerometer components. Estimates are completed 3 seconds after initial P-wave arrival at each station. Only the station estimates are telemetered to a central facility. The individual stations can broadcast some local warnings and actuate local shutdown functions. A central station receives the individual-station earthquake-parameter estimates and produces an integrated earthquake-parameter estimate 1 minute after receiving the initial estimates. The integrated estimate is used for purposes of emergency equipment deployment. The full system consists of five stations and a central facility (Nakamura, 1989). One advanced EAS concept, described by Heaton, consists of an area-wide distribution of strong-motion sensors that transmit raw data in real time to a central processing facility. The central processing facility estimates earthquake parameters such as zero time, location, and magnitude, and includes some measure of the reliability of these estimates. The earthquake parameter estimates are broadcast to the entire area and are rapidly updated as new information is obtained. A user
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Approximate Pages = 10 (250 words per page)