September 10, 1899 Earthquake: SE Alaska, Alaska, United States

The first shock [Sept 4, 1899] was moderately

severe at Yakutat, but extremely violent at Cape Yakataga, about 100 miles west of Yakutat. The latter was the great earthquake [Sept 10, 1899] which was accompanied

by important topographic changes. Both shocks were felt widely but over a largely unsettled region, so the total felt area is not known. In the central region there was no damage to life or property as there were no villages. A few prospectors and Indians were eyewitnesses.

The evidence of topographic change was unmistakable,

although no observations were made until a U.S. Geological Survey party studied the region 6 years later. During June 1899, the Harriman Scientific Expedition had visited the region to study glaciers. They took pictures of the area which showed no indication of such changes up to that

time. It was not difficult to measure the approximate

changes because there were a number of raised beaches, and dead barnacles and other shellfish were found everywhere. The maximum uplift of 47.5 feet was found on the west coast of Disenchantment Bay. Changes of 17 feet or more affected

a considerable area. In a few cases, there was depression

of l to 7 feet. The variations in uplift and depression indicate tilting of blocks. The net gain of land area was not more than 1/2 square mile.

There was a destructive tsunami in Yakutat Bay,

perhaps 35 feet high. Tsunamis also were observed

at other places along the Alaskan coast; a possible

seiche was observed in Lake Chelan, Wash. There were important changes in the glaciers. At the time of the earthquakes there were reports of volcanic eruptions, undoubtedly due to snow arising from great snowslides which often included rock and debris. This sudden additional load

change altered the regimen of the glaciers even 150 miles away. There was a sudden advance followed by important recessions. In some cases, greatly crevassed glacier fronts

were found 6 years later, showing that it had required this time for the fractured area to reach the sea.

There were several large aftershocks during September and the following months.

(above from reference #1128)

1899, September 10, 12:15 local time (20:15 UTC). There was a catastrophic earthquake with source at the tip of Yakutat Bay. Large block dislocations occurred along the fault system. The main dislocation was apparently the elevation of the mountainous block of the eastern shore of Yakutat Bay relative to the floor of the Gulf and the lowlands at Ocean Cape by up to 15 m. A secondary movement occurred along a smaller parallel fault, passing through Russel Fjord: its eastern shore rose somewhat above the eastern shore (as if the more continental block had shifted onto the littoral block of Yakutat Bay). The tectonic movements caused numerous large collapses and slides, including the breakup and collapse of glacier tongues (Reference #415).

Reference #88 lists earthquake on Sept 19, 1899, 21:41 UTC, 60 N, 140 W, shallow depth, magnitude 8.6.

Reference #1006 lists earthquake on Sept 10, 1899, 21:41 UTC, 60 N, 140 W, magnitude 8.6.