Historic Earthquakes
Yakutat Bay, Alaska
1899 09 10 17:04 UTC
Magnitude 7.4 (Foreshock)
1899 09 10 21:41 UTC
Magnitude 8.0 (Main Shock)
During September, the Yakutat Bay
region was shaken by a series of major earthquakes,
the most violent of which were felt at all settlements
within a radius of 400 kilometers. Several heavy shocks
occurred on September 4 and 10, but the main earthquake
that caused great topographic changes occurred at
21:41 UTC, September 10.
A U.S. Geological Survey team did not study the region until 6 years after the shocks, but the topographic changes were obvious. Dead barnacles and other shellfish were found everywhere, and several uplifted beaches were observed. A maximum uplift of 14.5 meters occurred on the west coast of Disenchantment Bay, and changes of 5 meters or more affected a large area. Subsidence of as much as 2 meters was observed in a few areas. Phenomena observed included surface faulting, avalanches, fissures, spouting from sand craterlets, and slight damage to buildings. A destructive tsunami 10.6 meters in height occurred in Yakutat Bay, and tsunamis also were observed at other places along the Alaskan coast.
The earthquake altered the regimen of glaciers in the area. The shattering of Muir Glacier started the rapid discharge of icebergs and the later retreat of this and other ice tongues in Glacier Bay. Avalanching resulted in the later advance of at least nine glaciers in Yakutat Bay and perhaps many others in more remote regions. Some severely crevassed glacier fronts, which were found 6 years later, had taken several years for the fractured parts to reach the sea.
The first earthquake on September 10 lasted 90 seconds and was heavier at Yakutat than that of September 4 (00:22 UTC). It was strong enough to throw people off their feet at Disenchantment Bay. The main earthquake on September 10 was felt over a largely unsettled region, and so the total felt area in unknown. Prospectors camped on Disenchantment Bay felt over 50 shocks on September 10, two of which were strong. Residents at Yakutat village also described as severe two of the many shocks observed that day. Ten or more earthquakes were felt in the Coast and Geodetic Survey camp near the Copper River delta, and several of them were violent. Several shocks were also felt on September 10 in the Chugach Mountains near Prince William Sound; five were reported about 300 kilometers to the northeast on the Yukon River; and several were felt to the southeast at Juneau and Skagway. Many large aftershocks occurred in September and the following months.
Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.
