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Powerful M7.9 earthquake hits Gulf of Alaska, triggers tsunami warnings

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A massive earthquake registered by the USGS as M7.9 hit the Gulf of Alaska at 09:31 UTC on January 23, 2018 (00:31 local time). The agency is reporting a depth of 25 km (15.5 miles). EMSC is reporting M8.0 at a depth of 10 km (6.2 miles). Tsunami warnings, watches and advisories were issued following the quake.  Over the next 3 hours, the USGS registered more than 20 aftershocks with magnitudes ranging from 2.5 to 5.3.

The epicenter was located 260.2 km (161.7 miles) SE of Chiniak (population 47) and 576.7 km (358.3 miles) S of Anchorage (population 291 826), Alaska, United States.

There are no people living within 100 km (62 miles). Some 14 000 people are estimated to have felt 14 000 light shaking.

Gulf of Alaska earthquake January 23, 2018 - ShakeMap

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Based on the preliminary earthquake parameters, widespread hazardous tsunami waves are possible, PTWC said 09:43 UTC.

Gulf of Alaska earthquake January 23, 2018 - Tsunami Warning and Watches
Tsunami travel time after M7.9 earthquake hits Gulf of Alaska, January 23, 2018

As of 12:35 AKST, a Tsunami Warning is in effect for:

BRITISH COLUMBIA, The Juan de Fuca Strait coast, the outer west coast of Vancouver Island, the central coast and northeast Vancouver Island, and the north coast and Haida Gwaii

SOUTHEAST ALASKA, The inner and outer coast from The BC/Alaska Border to Cape Fairweather, Alaska (80 miles SE of Yakutat)

SOUTH ALASKA AND THE ALASKA PENINSULA, Pacific coasts from Cape Fairweather, Alaska (80 miles SE of Yakutat) to Unimak Pass, Alaska (80 miles NE of Unalaska)

ALEUTIAN ISLANDS, Unimak Pass, Alaska (80 miles NE of Unalaska) to Attu, Alaska including the Pribilof Islands

A Tsunami Watch is in effect for:

  • CALIFORNIA, The coast from The Cal./Mexico Border to The Oregon/Cal. Border including San Francisco Bay
  • OREGON, The coast from The Oregon/Cal. Border to The Oregon/Wash. Border including the Columbia River estuary coast
  • WASHINGTON, Outer coast from the Oregon/Washington border to Slip Point, Columbia River estuary coast, and the Juan de Fuca Strait coast

The USGS issued a green alert for shaking-related fatalities and economic losses. There is a low likelihood of casualties and damage.

Overall, the population in this region resides in structures that are resistant to earthquake shaking, though vulnerable structures exist. The predominant vulnerable building types are unreinforced brick masonry and reinforced masonry construction.

Estimated population exposure to earthquake shaking

Gulf of Alaska earthquake January 23, 2018 - Estimated population exposure
Gulf of Alaska earthquake January 23, 2018 - Estimated population exposure table

Regional seismicity

Gulf of Alaska earthquake January 23, 2018 - Regional seismicity

Updates

At 12:13 UTC (03:13 AKST), the Tsunami Advisory was canceled for the coastal areas of South Alaska and the Alaska Peninsula. Residents are advised not to re-occupy hazard zones until local emergency officials indicate it is safe to do so.

Some areas may continue to see small sea level changes.

Between 09:31 and 12:48 UTC, the USGS registered a total of 24 earthquakes in this region, including M7.9. Magnitudes ranged from 2.5 to 7.9.

Gulf of Alaska earthquakes January 23, 2018

Featured image credit: USGS

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