A method for epicenter determination
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Abstract
The proposed method corrects for inhomogeneity in the azimuthal distribution of stations, by fitting the residuals to a cosine function of the azimuth. Early arrivals are assigned greater weights than late arrivals. The weights are optimized experimentally by using data from large explosions. Instead of tabulated travel times, polynomial approximations are utilized; hence the new programs require considerably less computer time and storage. The Longshot is normal to the axis of the trench, and is larger than previously reported. This means that the Longshot source term cannot be adequately accounted for by temperature differences between the sinking plate and the sorrounding mantle.
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References
ABE, K., 1972. Lithospheric normal faulting beneath the Aleutian trench, Phys. Earth Planet. Int., 5, 190-198. DOI: https://doi.org/10.1016/0031-9201(72)90091-X
CARDER, D. E., D. TOCHER, C. C. BUFE, S. STEWARD, J. D. EISLER, and· E. BERG, 1967. Seismic wave· arrivals from Longshot, 0o to 25°, Bull. Seism. Soc. Am, 57, 573-590. DOI: https://doi.org/10.1785/BSSA0570040573
CHINNERY, M. A. and M. N. TOKSOZ, 1967. P-wave velocities in the mantle below 700 km, Bull. Seis. Soc. Am., 5 7, 199-226.
CLARK, D. M., 1966. Long range seismic measurements --Longshot, UED Earth Sciences Div., Teledyne, Seismic Date Lab. Rept. 133. DOI: https://doi.org/10.21236/AD0627039
CLEARY, J., 1967. Azimuthal variation of the Longshot source term, Earth Planet. Sci. Letters, 3, 29-37. DOI: https://doi.org/10.1016/0012-821X(67)90007-6
DAVIES, D., and D. P. McKENZIE, 1969. Seismic travel-time residuals and plates, Geophys. J, 18, 51-63. DOI: https://doi.org/10.1111/j.1365-246X.1969.tb00261.x
DOUGLAS, A., and R. C. LILWALL, 1968. Does epicenter source bias exist? Nature, 220, 469-470. DOI: https://doi.org/10.1038/220469a0
ESPINOSA, A. F., 1971. An epicenter study of the underground nuclear explosion Longshot, J. Phys. Earth. 19, 283-287. DOI: https://doi.org/10.4294/jpe1952.19.283
FREEDMAN, H., 1966. The "little variable factor"; a statistical discussion of the reading of seismograms, Bull. Seis. Soc. Am., 56, 596-604. DOI: https://doi.org/10.1785/BSSA0560020593
GUTENBERG, B., and C. F. RICHTER, 1937. Materials for the study of deep-focus earthquakes, Bull. Seis. Soc. Am., 27, 157-184. DOI: https://doi.org/10.1785/BSSA0270030157
HERRIN, E., W. TUCKER, J. TAGGART, D. W. GORDON, and J. L. LOBDEL, 1968. Estimation of surface focus P travel times, Bull. Seis. Soc. Am., 58, 1273-1291. DOI: https://doi.org/10.1785/BSSA0580041273
HERRIN, E. and J. N. TAGGART, 1968. Regional variations in P travel times, Bull. Seis. Soc. Am. 58, 1325-1337. DOI: https://doi.org/10.1785/BSSA0580041325
JACOB, K., 1972. Global tectonics implications of anomalous seismic P travel-times from the nuclear explosion Longshot, J. Geophys. Res., 77, 2556-2573. DOI: https://doi.org/10.1029/JB077i014p02556
JEFFREYS, H., 1936. Travel times in seismology, Un. Géod. Géophys. Int. Série A, Trav. Scient., 14, 3-86.
KANAMORJ, H., 1968. Travel times to Japanese stations from Longshot and their geophysical implications, Bull. Earthq. Res. Inst. Tokyo Univ., 46, 841.
LAMBERT, D. G., D. H.VON SEGGERN, S. S. ALEXANDER, and G. A. GALET, 1969. The Longshot Experiment, vols. 1 and 2, Sci. Rept., Contract F33657-69-C-0913, Teledyne, Alexandria, Virginia.
LOMNITZ, C., 1971. Travel-time errors in the laterally inhomogeneous earth. Bull. Seis. Soc. Am., 61, 1639-1654. DOI: https://doi.org/10.1785/BSSA0610061639
LOMNITZ, C., and B. A. BOLT, 1967. Evidence on crustal structure from the CHASE V explosion and the Chico earthquake of May 24, 1966. Bull. Seis. Soc. Am., 57, 1093-1114.
LOMNITZ, C. y A. VARGAS G., 1969. Una nueva ecuación de regresión cuadrática para determinación de epicentros de temblores. Anales del Instituto de Geofísica, UNAM, Mexico, 14, 71-73.
NUTTLI, O. W., 1972. The amplitudes of teleseismic P waves, Bull. Seis. Soc. Am., 62, 343-356.
RINEHART, W. A., 1972. Rapid epicenter determination at the Palmer Seismological Observatory, NOAA Tech. Rept. ERL 236-ESL 21, 27-29.
TUCKER, W., E. HERRIN, and H. W. FREEDMAN, 1968. Some statistical aspects of the estimation of seismic travel times. Bull. Seis. Soc. Am., 58, 1243-1260. DOI: https://doi.org/10.1785/BSSA0580041243
WYSS, M. and J. N. BRUNE, 1967. The Alaska earthquake of 28 March 1964: a complex multiple rupture. Bull. Seis. Soc. Am., 57, 1017-1023. DOI: https://doi.org/10.1785/BSSA0570051017