Nuclear Explosions and the Gravity-Time Curve

Abstract

AN Askania gravimeter (GS.11) of the type using a static helical spring without astatization and damped aperiodically, having a period of 1.5 sec. and a sensitivity of about 10 cm./milligal., has been used at Hyderabad (lat. 17° 26′; long. 78° 27′) to record the variation of the value of gravity for a major part of a year with the view of studying Earth tides. The recording system is an optical one where a moving-coil galvanometer, the period of which is 17 sec., has been used, and the response of the gravimeter pendulum to the disturbances in the crustal regions of the Earth is magnified nearly 400,000 times, which is much more than that ordinarily achieved by seismometers. Our observation station has the advantage of being situated about 400 km, away from the coast on either side, which to a large extent eliminates the effect of Ocean Tides. In principle, a gravimeter is an extremely sensitive seismograph and hence, in addition to measuring the tidal force, it also acts as a monitor for earthquakes or similar seismic disturbances.