| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
OFFICE OF EARTHQUAKE STUDIES U.S. GEOLOGICAL SURVEY, 345MIDDLEFIELD ROAD, MENLO PARK, CALIFORNIA 94025
SEISMOGRAPHIC STATION DEPARTMENT OF GEOLOGY AND GEOPHYSICS UNIVERSITY OF CALIFORNIA, BERKELEY, CALIFORNIA 94720
Abstract
Foreshock activity preceded both the ML = 5.5 June 28, 1966 Parkfield, and the ML = 5.7 August 1, 1975 Oroville, California earthquakes. The PZ source displacement amplitude spectrum (0.5 Hz < f < 10 Hz) recorded at Priest Valley, California (
= 25 km) for an ML = 2.6 immediate Parkfield foreshock appears distinctive, characterized by a corner frequency fo = 2.5 Hz and an 
–1 higher-frequency spectral dependence; spectra for another immediate Parkfield foreshock (ML = 3.1), two nearby Parkfield aftershocks (ML = 3.0 and 2.9), and three nearby "normal" Parkfield earthquakes (ML = 2.6, 2.6, and 3.1) are all higher frequency with fo 
10 Hz. PZ and SZ signals (0.4 Hz 
f 10 Hz) recorded at Whiskeytown, California ( = 150 km) for an immediate ML = 3.8 Oroville foreshock have similar corner frequencies (fo 
2 to 4 Hz) and marginally smaller high-frequency roll-off rates than the corresponding phases for four nearby 3.6 ML 4.1 Oroville aftershocks; an analogous comparison failed to discriminate an earlier (June 28, 1975) ML = 3.5 Oroville foreshock from the same five aftershocks. This exercise in attempted foreshock identification, using high-quality data and the two largest central California earthquakes in many years, points up the extreme subtlety of any unique properties in radiated body waves and the resulting difficulty in characterizing foreshocks.
This article has been cited by other articles:
|
|
 |
|
  T. H. Webb Spatial clustering and stress drops of foreshocks of the February 1990 Tennyson and Weber, New Zealand, earthquakes Bulletin of the Seismological Society of America, December 1, 1994; 84(6): 1739 - 1753. [Abstract] [PDF]
|
|
|
|
|
|
H. K. GUPTA Are ris events of M greater double equals 5 preceded by a couple of foreshocks of M greater double equals 4? Bulletin of the Seismological Society of America, February 1, 1992; 82(1): 517 - 520. [PDF]
|
|
|
|
|
|
J. C. PECHMANN and B. S. THORBJARNARDOTTIR Waveform analysis of two preshock-main shock-aftershock sequences in Utah Bulletin of the Seismological Society of America, June 1, 1990; 80(3): 519 - 550. [Abstract] [PDF]
|
|
|
|
|
|
F. R. ZUNIGA, M. WYSS, and M. E. WILSON Apparent stresses, stress drops, and amplitude ratios of earthquakes preceding and following the 1975 Hawaii MS = 7.2 main shock Bulletin of the Seismological Society of America, February 1, 1987; 77(1): 69 - 96. [Abstract] [PDF]
|
|
|
|
|
|
F. SCHERBAUM and C. KISSLINGER Variations of apparent stresses and stress drops prior to the earthquake of 6 May 1984 (mb = 5.8) in the Adak Seismic Zone Bulletin of the Seismological Society of America, December 1, 1984; 74(6): 2577 - 2592. [Abstract] [PDF]
|
|
|
|
|
|
L. M. JONES Foreshocks (1966-1980) in the San Andreas system, California Bulletin of the Seismological Society of America, August 1, 1984; 74(4): 1361 - 1380. [Abstract] [PDF]
|
|
|
|
|
|
H. K. GUPTA and H. M. IYER Are reservoir-induced earthquakes of magnitude greater double equals 5.0 at Koyna, India, preceded by pairs of earthquakes of magnitude greater double equals 4.0? Bulletin of the Seismological Society of America, June 1, 1984; 74(3): 863 - 873. [Abstract] [PDF]
|
|
|
|
|
|
W. H. BAKUN and T. V. MCEVILLY P-wave spectra for ML 5 foreshocks, aftershocks, and isolated earthquakes near Parkfield, California Bulletin of the Seismological Society of America, April 1, 1981; 71(2): 423 - 436. [Abstract] [PDF]
|
|
|
|
|
|
M. ISHIDA and H. KANAMORI Temporal variation of seismicity and spectrum of small earthquakes preceding the 1952 Kern County, California, earthquake Bulletin of the Seismological Society of America, April 1, 1980; 70(2): 509 - 527. [Abstract] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
