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Observed times of the Montana earthquakes, 1935

Gutenberg, B. and Richter, C. F. (1938) Observed times of the Montana earthquakes, 1935. Bulletin of the Seismological Society of America, 28 (2). pp. 85-87. ISSN 0037-1106.

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Unusual interest attaches to seismograms of the earthquakes destructive at Helena, Montana, in October, 1935. The two principal shocks, at 4 h on October 19 and 18 h on October 31 (G.C.T.), were large enough for the P phases to be recorded at distances up to about 90°. The similarity of the seismograms, and the constancy of time differences between corresponding phases of the two shocks, show that they must have had nearly the same epicenter and focal depth. This epicenter must have been very close to the city of Helena; the considerable damage, and the great number of small associated shocks reported as felt and even as strong, are good noninstrumental evidence of this. In addition, part of the second large shock, and a large number of small shocks, were recorded at Helena by the United States Coast and Geodetic Survey. The S-P interval on these records is about one or two seconds.

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Additional Information:© 1938 by the Seismological Society of America. Manuscript received for publication January 17, 1938.
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Balch Graduate School of the Geological Sciences248
Issue or Number:2
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47929
Deposited By: George Porter
Deposited On:04 Aug 2014 22:28
Last Modified:18 Mar 2020 17:32

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