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AAPG Bulletin

Abstract


Volume: 39 (1955)

Issue: 12. (December)

First Page: 2505

Last Page: 2514

Title: Orleansville Earthquake and Turbidity Currents

Author(s): Bruce C. Heezen (2), Maurice Ewing (3)

Abstract:

An earthquake of magnitude 6.7 violently shook the area near Orleansville, Algeria, on September 9, 1954. The area of appreciable damage extended 15 miles from the epicenter, and following the earthquake five submarine cables lying on the floor of the Mediterranean Sea broke at distances of 40-70 miles northwest of the epicenter. Since the cables were broken at a considerable distance from the area in which appreciable damage was inflicted by seismic energy, it is believed that the cables were broken by a mass of sediment shaken loose by the earthquake but moved down the slope and far out into the abyssal plain by its own potential energy. This interpretation is similar to that advanced for the cable breakage south of the epicenter of the 1929 Grand Banks earthquake.

Evidence in favor of this interpretation has been published by Bourcart who reports on a sediment core taken on the Balearic abyssal plain 80 miles east of the area in which the cables were broken. Petrographic studies indicate that a sand bed in this core had come from the massif "Petite Kabylie" in Algeria. The lack of rounding of the grains excluded eolian or beach origin of the material, and led to the conclusion that it had been carried out on the abyssal plain by a turbidity current. The Orleansville earthquake triggered a turbidity current in sediment lying on the steep continental slope. This current ran out across the abyssal plain, breaking each successive cable, and deposited its load on the abyssal plain. The events associated with the Orleansville earthquake and the break ng of the Mediterranean cables provide further support for the modern occurrence of turbidity currents, the turbidity current origin of abyssal plains and deep sea sands, and further indicate the importance of the earthquake trigger effect on the formation of turbidity currents in sediments on steep submarine slopes.

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