The effect of rupture complexity on estimates of source size

A general technique is proposed for estimating rupture geometry from measurements of body wave durations, wherein measurements of the overall signal duration or the duration of a single pulse identified in all of the arrivals are inverted to estimate the geometry of the overall rupture or of a specific subevent, respectively. The complexity of a waveform is determined by comparing the overall signal duration to the duration of the most prominent pulse in the waveform; this complexity is used to estimate the ratio of the average rupture velocity to the subevent rupture velocity. The shear waves radiated by eight moderate (3.6≤ML≤4.9) multiply recorded aftershocks of the 1975 Oroville, California, earthquake are analyzed using measurements of the corner frequency, the characteristic frequency, the pulse duration, and the signal duration. Comparison of these four different estimates of source size indicates that the corner frequency and the characteristic frequency are more sensitive to the dominant subevent size than to the overall event size. The difference between the estimates of source size determined from the signal duration measurements and the spectral measurements increases as the rupture complexity increases.

[1]  Robin K. McGuire,et al.  The character of high-frequency strong ground motion , 1981 .

[2]  V. E. Benes,et al.  Statistical Theory of Communication , 1960 .

[3]  Francis T. Wu,et al.  Source mechanism of February 4, 1965, Rat Island earthquake , 1973 .

[4]  M. Wyss,et al.  The Alaska earthquake of 28 March 1964: A complex multiple rupture , 1967 .

[5]  J. Brune.  Tectonic stress and the spectra of seismic shear waves from earthquakes , 1970 .

[6]  R. Madariaga.  Dynamics of an expanding circular fault , 1976, Bulletin of the Seismological Society of America.

[7]  Thomas C. Hanks,et al.  The faulting mechanism of the San Fernando Earthquake , 1974 .

[8]  Mihailo D. Trifunac,et al.  Complexity of energy release during the Imperial Valley, California, earthquake of 1940 , 1970 .

[9]  L. Johnson,et al.  Near-field observations and source parameters of central California earthquakes , 1974, Bulletin of the Seismological Society of America.

[10]  Keiiti Aki,et al.  Fault plane with barriers: A versatile earthquake model , 1977 .

[11]  M. Husseini,et al.  Rupture velocity and radiation efficiency , 1976 .

[12]  Paul G. Silver,et al.  Retrieval of source-extent parameters and the interpretation of corner frequency , 1983 .

[13]  J. Boatwright,et al.  A spectral theory for circular seismic sources; simple estimates of source dimension, dynamic stress drop, and radiated seismic energy , 1980 .

[14]  N. A. Haskell.  Total energy and energy spectral density of elastic wave radiation from propagating faults , 1964 .

[15]  T. Hanks,et al.  Strong-motion accelerograms of the Oroville aftershocks and peak acceleration data , 1978, Bulletin of the Seismological Society of America.

[16]  J. Boatwright,et al.  Broadband analysis of the extended foreshock sequence of the Miyagi-Oki earthquake of 12 June 1978 , 1982 .

[17]  J. Lahr,et al.  The August 1975 Oroville earthquakes , 1976, Bulletin of the Seismological Society of America.

[18]  J. Boatwright,et al.  Investigation of two high stress drop earthquakes in the Shumagin Seismic Gap, Alaska , 1980 .

[19]  George L. Choy,et al.  The rupture characteristics of two deep earthquakes inferred from broadband GDSN data , 1981 .

[20]  W. Savage,et al.  Catalog of Oroville, California, earthquakes; June 7, 1975 to July 31, 1976 , 1979 .

[21]  Time-domain determination of earthquake fault parameters from short-period P-waves , 1976 .

[22]  A. G. Brady,et al.  Strong-Motion Accelerograms of the Oroville, California, aftershocks: Data processing and the aftershock of 0350 August 6, 1975 , 1980 .

[23]  J. Boatwright.  Quasi-dynamic models of simple earthquakes: Application to an aftershock of the 1975 Oroville, California, earthquake , 1981 .