Fundamental Relations in Seismometry

Abstract

The equations for dynamical equilibrium of a geophone are derived by means of the Lagrange method and applied to the particular cases of a moving armature geophone, moving conductor geophone, and electrostatic geophone. The galvanometer for seismic recording is usually of the moving coil type and its equations are similar to those of a moving conductor geophone. The magnetic type geophone as well as the galvanometer consist essentially of two dynamical systems characterized by an asymmetric coupling: “the transducing resistance.” A brief analysis is given of the problem of determining the response of a seismograph to a given earth motion.

Mathematical problems in seismology

“…In galvanometrlc instruments the fact that the galvanometer is not tightly coupled to the pendu lum means that the number of degrees of freedom is Increased and the order of the differential equation of motion is higher than that (two) of the mechanical instrument. The theory of the galvanometrlc seismograph has been studied by Galitzin [68], Wenner [69], Sohon [8, part II], Benioff [70], Blake [71], Grenet and Coulomb [72], Scherbatskoy and Neufeld [73], and others, but many interesting problems are yet to be discussed.…”