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A linear strain seismograph

Benioff, Hugo (1935) A linear strain seismograph. Bulletin of the Seismological Society of America, 25 (4). pp. 283-309. ISSN 0037-1106.

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The response of hitherto known practical forms of seismographs depends upon the relative motion of a pendulum and the moving ground to which its supporting structure is fastened. The various kinds of seismographs differ in the type of pendulum used, such as gravity, spring, torsion, and/or they differ in the type of magnifying and recording elements which they employ. They all measure or indicate the vibratory motion of the ground at a giver point. In contrast to these earlier forms, the strain seismograph is a nonpendular instrument. It does not respond directly to vibratory movements Its operation depends upon variations in the distance between two points of the ground. Such variations or linear strains are set up by seismic waves. A schematic drawing of the seismometer is shown in figure 1. A and B are two piers separated by a distance of 20 meters. One end of the rod R is rigidly fastened to the pier B. The other end extends to within a short distance of pier A. Earth strains resulting from a seismic wave train produce variations in the separation of the two piers, and these variations are observable as changes in the distance between the free end of the rod and pier A. These small movements of the end of the rod relative to the adjacent pier actuate an electromechanical transducer which generates an e.m.f, proportional to the rate of change of the relative displacement. Recording is accomplished by means of galvanometers. A photograph of the seismometer is reproduced in figure 2.

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Additional Information:Copyright © 1935, by the Seismological Society of America. The instrument is mentioned and described in the Carnegie Institution of Washington Year Book No. 29, 1929-30, and subsequent numbers. It was also described in a paper read before the meeting of the Seismological Society of America held in Pasadena in June, 1931. The present paper was submitted in partial fulfillment of the thesis requirement for the degree of Doctor of Philosophy, at the California Institute of Technology. Manuscript received for publication July 20, 1935.
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Balch Graduate School of the Geological Sciences190
Issue or Number:4
Record Number:CaltechAUTHORS:20140804-155300843
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47941
Deposited By: George Porter
Deposited On:05 Aug 2014 14:49
Last Modified:21 Feb 2020 15:58

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