Abstract

The epicenter of the Suva earthquake of Sept. 14, 1953, (U.S.C. & G.S. data: H = 00h26m36s UT 1812°S,17812°E;M=634; h about 60 kilometers) has been redetermined on the basis of landslide intensity, isoseismic analysis, damage criteria, the bathymetry of the epicentral zone, and by other means. The new epicenter is at 18.2° S, 178.3° E with an estimated probable error of five miles. Employing the new epicenter, P residuals of 15 stations (U.S.C. & G.S. data) were computed, assuming a normal and a 60 kilometer depth of focus. A normal depth of focus was decidedly the most likely.

Arrival times of the ensuing tsunami at various points were reconciled to show that the tsunami had an extended source from Suva harbor to Beqa island. The tsunami was clearly caused by the slumping of marine sediments immediately after the earthquake. The direct action of the earthquake produced small waves that served as warnings on Beqa and Kadavu islands. These waves are presumed to have been created by the vibration of the reef against the water. The destructive waves, arriving later, were produced by slumping effects originating on the edge of the marginal shelf. Their observed arrivals are consistent with this mechanism.

The bathymetry of the affected area was resurveyed and bottom changes up to 300 feet vertically were found. At a distance of more than 30 miles from the slumps, submarine cables were disrupted and displaced by as much as 13,000 feet. It is inferred that these effects were caused by turbidity currents travelling down a gradient of about 5 per cent for the first 10 miles and nearly flat thereafter.

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