HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) References Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by GUTENBERG, B. Search for Related Content GeoRef GeoRef Citation

Travel times of principal P and S phases over small distances in southern California^*

CALIFORNIA INSTITUTE OF TECHNOLOGY, PASADENA, CALIFORNIA

Abstract

Study of arrival times of the principal phases in fifty of the larger and better recorded earthquakes in southern California resulted in the following travel times t (seconds) and apparent velocities V (km/sec.): = epicentral distance, D² = ² + h², h = focal depth. x and y depend on the region; the following are characteristic valuesThe average true velocities of Py and Sy are about one-third of one per cent, those of Pn and Sn about one-half of one per cent, smaller than the corresponding apparent velocities. In the uppermost 50 km. the velocity increases with depth. The order of magnitude of this increase is roughly 1 per cent per 10 kilometers, but larger in the uppermost one or two kilometers. It can be found from a study of amplitudes (Gutenberg, 1943c); its effect on the travel times exceeds the limits of error by too small an amount to be ascertained beyond doubt from the data of the present paper. The curvature of the earth can be disregarded within the range of distances used (in general not exceeding 800 km.). The effect of "mountain roots" on the travel times of Pn and Sn is investigated.

Reproduction of travel-time curves and recalculation of the thickness of the various layers must wait until a study of other (especially reflected) recorded phases now under way is finished. Preliminary values are 18 km. for the thickness of the granitic layer with small local variations, and about 35 km. for the total of the crustal layers in the coastal areas of southern California with an increase inland approaching twice that amount under the Sierra Nevada.

Footnotes

^* Manuscript received for publication April 12, 1943.

This article has been cited by other articles:

				R. A. ERGAS and D. D. JACKSON Spatial variation of crustal seismic velocities in southern California Bulletin of the Seismological Society of America, June 1, 1981; 71(3): 671 - 689. [Abstract] [PDF]

				K. L. KAILA, P. R. REDDY, and H. NARAIN Crustal structure in the Himalayan foothills area of north India, from 'P' wave data of shallow earthquakes Bulletin of the Seismological Society of America, April 1, 1968; 58(2): 597 - 612. [Abstract] [PDF]

				E. S. HUSEBYE Correction analysis of Jeffreys-Bullen travel time tables Bulletin of the Seismological Society of America, December 1, 1965; 55(6): 1023 - 1038. [Abstract] [PDF]

				J. M. NORDQUIST A catalog of Southern California earthquakes, and associated electronic data processing programs Bulletin of the Seismological Society of America, June 1, 1964; 54(3): 1003 - 1011. [Abstract] [PDF]

				H. J. MILLER The Oklahoma earthquake of April 9, 1952 Bulletin of the Seismological Society of America, October 1, 1956; 46(4): 269 - 279. [Abstract] [PDF]

				P. DEHLINGER Shear-wave vibrational directions and related fault movements in Southern California Earthquakes Bulletin of the Seismological Society of America, April 1, 1952; 42(2): 155 - 173. [Abstract] [PDF]

				C. F. RICHTER and J. M. NORDQUIST Instrumental study of the Manix Earthquakes Bulletin of the Seismological Society of America, October 1, 1951; 41(4): 347 - 388. [Abstract] [PDF]

				B. GUTENBERG Revised travel times in southern California Bulletin of the Seismological Society of America, April 1, 1951; 41(2): 143 - 163. [Abstract] [PDF]

				C. F. RICHTER Velocities of P at short distances Bulletin of the Seismological Society of America, October 1, 1950; 40(4): 281 - 289. [Abstract] [PDF]

				S. T. MARTNER Observations on seismic waves reflected at the core boundary of the earth Bulletin of the Seismological Society of America, April 1, 1950; 40(2): 95 - 109. [Abstract] [PDF]

				S. T. MARTNER The Dominguez Hills, California, earthquake of June 18, 1944 Bulletin of the Seismological Society of America, April 1, 1948; 38(2): 105 - 119. [Abstract] [PDF]

				B. GUTENBERG On the layer of relatively low wave velocity at a depth of about 80 kilometers Bulletin of the Seismological Society of America, April 1, 1948; 38(2): 121 - 148. [Abstract] [PDF]

				J. H. HODGSON Analysis of travel times from rockbursts at Kirkland Lake, Ontario Bulletin of the Seismological Society of America, January 1, 1947; 37(1): 5 - 17. [PDF]

				B. GUTENBERG Reflected and minor phases in records of near-by earthquakes in southern California Bulletin of the Seismological Society of America, July 1, 1944; 34(3): 137 - 160. [PDF]