Earthquakes instrumentally recorded in artesian wells*

Water-level fluctuations produced by earthquakes have been instrumentally recorded in many observation wells. Such fluctuations are produced only in wells that penetrate water which is confined under pressure. Most of the instruments that produced these earthquake records are automatic water-stage recorders operating with floats on the water surface in a well. In such recording devices water must move into or out of the bottom of the well to produce records of fluctuation. Earthquake disturbances are rapid and oscillating and float recorders therefore do not quantitatively record such disturbances. During the earthquakes of March 12 and April 14, 1934, a recording pressure gage was in operation on an artesian well in Ogden Valley, Utah. The fluctuation of pressure recorded during these earthquakes was about 5.5 and 3.8 pounds per square inch, respectively. This instrument is so constructed that very little water moves into or out of the well when changes of hydrostatic pressure take place, and thus the rapidly oscillating changes in hydrostatic pressure that occur during earthquakes are recorded. This suggests a quantitative method of recording earthquakes that may yield data not given by present methods.