Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted 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 HASEGAWA, H. S. Articles by STEPHENS, C. D. Search for Related Content GeoRef GeoRef Citation

Fault parameters of the St. Elias, Alaska, earthquake of February 28, 1979

EARTH PHYSICS BRANCH DEPARTMENT OF ENERGY, MINES AND RESOURCES, OTTAWA, Canada, K1A 0Y3
U.S. GEOLOGICAL SURVEY, 345 MIDDLEFIELD ROAD, MENLO PARK, CALIFORNIA 94025

Abstract

Fault parameters of the M_s 7.1 St. Elias, Alaska, earthquake of February 28, 1979, are determined from an analysis of P-wave first motions, fundamental-mode surface waves, and aftershock data. The preferred P-wave nodal plane has a shallow (12°) angle of dip and indicates underthrusting in a northerly (N13°W) direction, which is also close to the azimuth (N8°W) of the deviatoric compression (P) vector. Aftershock activity during the 24-hr interval immediately following the main shock extends over an area of 3200 km², which is taken to represent the fault area of the main shock. Because aftershock activity outlines a fault area with nonrectangular geometry, fault length (50 to 80 km) and width (50 to 65 km) are not well defined. Estimates of focal depth from aftershock activity fall in the range 10 to 20 km, which surface-wave analysis is unable to restrict further. For the main shock, seismic moment, M_o, is 2.5 x 10²⁷ dyne-cm (0.25 x 10²¹ N.m) and average dislocation, 2 meters. Average rupture velocity falls in the range 2.5 to 3 km/sec. Apparent stress, , is 5 bars (0.5 MPa) and stress drop, , 35 bars (3.5 MPa). These values are considered typical of large-magnitude interplate earthquakes.

This article has been cited by other articles:

				R. L. KOVACH and G. C. BEROZA Seismic potential from reverse faulting on the San Francisco Peninsula Bulletin of the Seismological Society of America, April 1, 1993; 83(2): 597 - 602. [PDF]

				W. B. JOYNER A scaling law for the spectra of large earthquakes Bulletin of the Seismological Society of America, August 1, 1984; 74(4): 1167 - 1188. [Abstract] [PDF]

				N. N. BISWAS and K. AKI Characteristics of coda waves: Central and southcentral Alaska Bulletin of the Seismological Society of America, April 1, 1984; 74(2): 493 - 507. [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]

				R. BULAND and J. TAGGART A mantle wave magnitude for the St. Elias, Alaska, earthquake of 28 February 1979 Bulletin of the Seismological Society of America, August 1, 1981; 71(4): 1143 - 1159. [Abstract] [PDF]

				C. D. STEPHENS, J. C. LAHR, K. A. FOGLEMAN, and R. B. HORNER The St. Elias, Alaska, earthquake of February 28, 1979: Regional recording of aftershocks and short-term, pre-earthquake seismicity Bulletin of the Seismological Society of America, October 1, 1980; 70(5): 1607 - 1633. [Abstract] [PDF]