Fluctuations of ground-water levels in Puerto Rico resulting from earthquakes (1959-1961)

During the Chilean earthquake of May 22, 1960, intensity 8.5, 4 of 8 wells in Puerto Rico equipped with automatic recorders, recorded seismic fluctuations. The maximum double amplitude, 0.05 ft, was recorded at a well in bedrock near Coamo. Double amplitudes in 3 other wells ranged from slightly less than .01 to .02 ft. Following the Puerto Rico earthquake of Aug. 2, 1961, intensity about 5.5, seismic fluctuations were recorded in 3 of 9 wells. The maximum double amplitude of these fluctuations ranged from .07 ft in a well in alluvium to .01 ft each in 2 wells in bedrock. Two wells showed seismic responses to both earthquakes and in both cases greaterfluctuations resulted from the more distant but more intense Chilean quake. No lasting changes in water levels or yields of wells have been recorded as a result of quakes occurring during the period of record.