Waves and Currents Recorded by Electromagnetic Barographs

Abstract

For some 40 years it has been known as a result of seismograph observations that the ground is never at rest. One of the characteristic types of ground unrest appears in the form of fairly regular wave trains having predominant periods in the range 4 to 10 seconds. These have been observed over the whole earth. Two hypotheses have been suggested as to the origin of these "microseisms". One that they are a result of the action of large surface waves on a steep shore. The other assumes that the ground disturbances are produced by synchro-nous pressure variations of atmosphere over the ocean acting through the water to the ocean bottom. In order to investigate this hypothesis J. B. Macelwane and J. E. Ramirez built an electromagnetic microbarograph. To date they have not published any results bearing on this question.