UTC time | 1958-04-07 15:30:45 |
---|---|
ISC event | 884131 |
USGS- ANSS | ComCat |
Magnitude | 7.3 Ms |
Depth | 6.0–7.0 km |
Epicenter | 65°54′54″N 156°20′35″W / 65.915°N 156.343°W |
Type | Thrust (intraplate) |
Areas affected | Northern Alaska |
Total damage | Minor |
Max. intensity | MMI VIII (Severe) |
Aftershocks | Yes |
Casualties | None |
The 1958 Huslia earthquake on April 7 struck an unusual part of Alaska, near the city of Huslia, about 415 km from Fairbanks. The Ms 7.3 [1] earthquake is one of two magnitude 7.0 or greater earthquakes recorded north of 65° latitude, the other being the 1933 Baffin Bay earthquake, and is one of the strongest earthquakes within the interior of the state. [2] The earthquake was a result of compression of the crust due to the subduction of the Pacific Plate under the North American Plate. [3]
The earthquake was unusual for its location because it was situated in a geologically stable part of the North American Plate, more than 965 km from the Aleutian subduction zone; the nearest plate boundary. There are no known visible fault traces in the immediate vicinity of the earthquake other than a thrust fault under the Brooks Range and another strike-slip feature known as the Kaltag Fault. The Koyukuk Basin consists of accretion of volcanic arcs from the Middle Jurassic to Early Cretaceous. P-wave analysis suggests that the earthquake was a result of thrust faulting at a depth of 6 km. [4] The fault plane solution is either a shallow north-northwest dipping plane or a steep south-southwest dipping plane. [5] The earthquake was followed by two moderate aftershocks on April 8 and 12 respectively. [6] [7]
Shaking from the earthquake reached VIII (Severe) on the Modified Mercalli intensity scale at its maximum within a radius of 40 to 50 miles. Meanwhile shaking in general was felt for an area of 150,000 square miles. [8] Ice cracks and liquefaction was reported for an area of 400 square miles. Pressure ridges, lakes thawing, and craters 20 feet across and 6 feet deep were reported during a survey. In Huslia, minor damage to roofs and foundations. An old building in Stevens Village was declared unsafe after it was seen that poles supporting its roof had split and broken. Ice from a frozen river cracked and ground fissures opened at Tanana. More damage was reported in other towns. [8]