![]() ![]() City, State, and Federal agencies, as well as other organizations and individuals, gave unstintingly of their time and facilities. Response to the disaster was immediate and decisive. After the earth- quake, fill, consisting of silt and sand dredged from the head of the bay, was pumped onto part of the lagoon area and also on land at the northwest corner of the bay. The Seward waterfront had been extended before the earthquake by adding artificial fill consisting of loose sand and gravel part of the lagoon area had been filled with refuse. Rock and snow avalanches, debris flows, and creep of talus deposits characterized slide activity on the steeper slops. ![]() The earthquake reactivated old slides and trigged new ones in the mountains. They consist mostly of silt, sand, and fine gravel, and lesser amounts of clay-size particles. Near the head of Resurrection Bay, the alluvium is underlain by at least 75 feet of marine deltaic sediments, which are in turn underlain by 600 or more feet of drift in the deepest part of the bedrock valley.īeach, deltaic, and estuarine sediments, deposited on intertidal flats at the head of the bay and along far1 margins that extend into the bay, arc mapped as intertidal deposits. In the axial part of the valley it is probably more than 100 feet thick. Valley alluvium, deposited chiefly by the Resurrection River, consists mostly of coarse sand and fine to medium gravel. Smaller fans at the mouths of several canyons have steep gradients and considerable local relief. The fan deposits range in thickness from about 100 feet to possibly several hundred feet and, at least in some places, lie on a platform of compact drift. The larger fans-composed chiefly of loosely compacted and poorly sorted silt, sand, and gravel-form broad aprons having low gradients. Some, including the one upon which Seward built, project into Resurrection Bay, and deltaic-type deposits form their distal edges. Glacial outwash and stratified ice-contact deposits constitute the remainder of the drift deposits.įans and fan-deltas have been deposited at the valley mouths of tributary streams. The till is predominantly silt and sand and lesser amounts of clay-size particles, gravel, cobbles, and boulders. The drift deposits consist chiefly of till that forms moraines along the lower flanks of the Resurrection River valley and up tributary valleys. Most of these units intergrade and were deposited more or less contemporaneously. Surficial deposits of the area hare been divided for mapping into the following units: drift deposits, alluvial fan deposits, valley alluvium, intertidal deposits, landslide deposits, and artificial fill. So major faults were found in the mapped area, but small faults, shear zones, and joints are common. Locally, the rocks are complexly folded or contorted. Beds and cleavage of the rocks commonly dip 70° W. The main structural trend in the mapped area, where the rocks consist almost entirely of graywacke and phyllite, is from near north to N. ![]() Seward lies on the axis of the Chugach Mountains geosyncline. The total cost to replace the destroyed public and private facilities was estimated at $22 million. The harbor facilities were almost completely destroyed, and the entire economic base of the town was wiped out. Eighty-six houses were totally destroyed and 260 were heavily damaged. Thirteen people were killed and five were injured as a result of the earthquake. ![]() Tectonic subsidence of about 3.6 feet resulted in low areas being inundated at high tide. Damage from strong ground motion itself was comparatively minor. Slide-generated wares, possibly seiche waves, and seismic sea waves crashed onto shore ware runup was as much as 30 feet above mean lower low water and caused tremendous damage fire from burning oil tanks added to the destruction. Additional ground was fractured in the Forest Acres subdivision and on the alluvial floor of the Resurrection River valley fountaining and sand boils accompanied the ground fracturing. Fractures ruptured the ground for'severa1 hundred feet back from the landslide scarps. During the shaking, a strip of land 50–400 feet wide along the Seward waterfront, together with docks and other harbor facilities, slid into Resurrection Bay as a result of large-scale submarine landsliding. Strong ground motion at Seward lasted 3–4 minutes. Its epicenter was in the northern part of the Prince William Sound area focal depth was 20–50 km. The Alaska earthquake of March 27, 1964, magnitude approximately 8.3–8.4, began at 6:36 p.m. It is one of the few ports in south-central Alaska that is ice free all year, and the town’s economy is almost entirely dependent upon its port facilities. The greater part of Seward is built on an alluvial fan-delta near the head of Resurrection Bay on the southeast coast of the Kenai Peninsula. Seward, in south-central Alaska, was one of the towns most devastated by the Alaska earthquake of March 27, 1964. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |