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 JENNINGS, P. C. Articles by KANAMORI, H. Search for Related Content GeoRef GeoRef Citation

Determination of local magnitude, M_L, from seismoscope records

EARTHQUAKE ENGINEERING RESEARCH LABORATORY CALIFORNIA INSTUTUTE OF TECHNOLOGY, PASADENA, CALIFORNIA 91125
SEISMOLOGICAL LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY, PASADENA, CALIFORNIA 91125

Abstract

A method is presented for determining the local magnitude, M_L, from records from seismoscopes and similar instruments. The technique extrapolates the maximum response of the standard Wood-Anderson seismograph, which determines M_L, from the maximum response of the seismoscope. The standard deviation of the steady-state response of an oscillator subjected to white noise excitation is used to derive a relation correcting for the different periods, dampings, and gains of the two instruments. The accuracy of the method is verified by application to data from the San Fernando and Parkfield earthquakes wherein both accelerograph and seismoscope records are available from the same sites. The accelerograms are used to synthesize Wood-Anderson responses whose maxima are compared to those extrapolated from the seismoscope data. In both earthquakes, the average magnitudes and standard deviations determined by the two approaches are very nearly equal.

The method is then applied to the strong-motion data from the Managua, Nicaragua earthquake of December 23, 1972 (M_S = 6.2, m_b = 5.6). A value of M_L = 6.2 is indicated from the seismoscope and accelerograph data. The next application is to the Guatemala earthquake of February 4, 1976 (M_S = 7.5, m_b = 5.8). The only seismic instrumentation available for determining M_L is a seismoscope record from Guatemala City, which indicates M_L = 6.9 when a representative distance of about 35 km is used. As a final example, the records obtained during the 1906 San Francisco earthquake from the Ewing duplex pendulum seismograph at Carson City, Nevada and the simple pendulum at Yountville, California are analyzed. After restoring the Carson City instrument, its period and damping were determined experimentally as were the period and damping of a similar instrument in the London Science Museum. On the basis of the strong-motion records from Carson City and Yountville, it is estimated that the local magnitude of the 1906 earthquake lies in the range to 7.

The use of seismoscope data further extends the instrumental base from which M_L can be determined and allows the rapid determination of M_L in earthquakes where seismoscope data are available. The applications in this study provide further instrumental evidence for the saturation of M_L in the 7 to range, with the value of 7.2 for the Kern County earthquake of 1952, the largest so far determined.

This article has been cited by other articles:

				D. J. WALD, H. KANAMORI, D. V. HELMBERGER, and T. H. HEATON Source study of the 1906 San Francisco earthquake Bulletin of the Seismological Society of America, August 1, 1993; 83(4): 981 - 1019. [Abstract] [PDF]

				A. A. KIRATZI and B. C. PAPAZACHOS Magnitude scales for earthquakes in Greece Bulletin of the Seismological Society of America, June 1, 1984; 74(3): 969 - 985. [Abstract] [PDF]

				D. M. BOORE Use of seismoscope records to determine ML and peak velocities Bulletin of the Seismological Society of America, February 1, 1984; 74(1): 315 - 324. [Abstract] [PDF]

				P. C. JENNINGS and H. KANAMORI Effect of distance on local magnitudes found from strong-motion records Bulletin of the Seismological Society of America, February 1, 1983; 73(1): 265 - 280. [Abstract] [PDF]

				J. ENRIQUE LUCO A note on near-source estimates of local magnitude Bulletin of the Seismological Society of America, June 1, 1982; 72(3): 941 - 958. [Abstract] [PDF]

				W. B. JOYNER and D. M. BOORE Peak horizontal acceleration and velocity from strong-motion records including records from the 1979 imperial valley, California, earthquake Bulletin of the Seismological Society of America, December 1, 1981; 71(6): 2011 - 2038. [Abstract] [PDF]

				A. F. ESPINOSA Attenuation of strong horizontal ground accelerations in the Western United States and their relation to ML Bulletin of the Seismological Society of America, April 1, 1980; 70(2): 583 - 616. [Abstract] [PDF]

				H. KANAMORI A semi-empirical approach to prediction of long-period ground motions from great earthquakes Bulletin of the Seismological Society of America, December 1, 1979; 69(6): 1645 - 1670. [Abstract] [PDF]