Sensor for gravitational field and its application to measures against large earthquake disasters

A gravitational field sensor is described as well as its application to provide warnings so that measures can be taken to mitigate the effects large earthquakes. One of the most promising sensors uses the principle of Michelson interferometry. Assuming a great earthquake (magnitude M=7) where the epicentral distance to a city is long, for instance, /spl sim/100 km the sensor will respond to the turbulent gravitational field with about 20 dB sensitivity 7 seconds before the seismic wave (primary wave) arrival. Even in a short period such as this it will be possible to take some safety measures like turning off the gas and nuclear reactors, bringing trains to a sudden stop, etc.<
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