A powerful 7.8 magnitude earthquake hit some parts of the Alaska Peninsula on Tuesday night. According to the details provided by seismologists, the earthquake tremors were felt shortly after 10 p.m. on Tuesday.
The epicenter of the earthquake was about 75 miles south of Chignik at a depth of about 17 miles and set off a tsunami warning from the Aleutian Islands to the western Kenai Peninsula. Evacuations were carried out but very little damage to communities was reported and the tsunami warning was canceled around 12.30 a.m.
The National Tsunami Warning Center said that the tsunami no longer poses a threat though “some areas may continue to see small sea-level changes”. People have been advised against going to hazard zones till local administrators give the clearance.
James Gridley, Director of the National Tsunami Warning Center in Palmer, said in an interview early Wednesday, “Our procedures put us into a warning even if we haven’t measured a tsunami wave — we imply that there is until we know better.”
Michael West, a State seismologist with the Alaska Earthquake Center, explained that the minimal damage despite the great magnitude was due to the epicenter being off the shore. He compared it to the Great Alaska Earthquake of 1964 and said that these kinds of tremors were typical to the area.
The tsunami warning sirens prompted Alaskans to take refuge on higher ground in communities as widespread as Unalaska, Kodiak, Homer and Sand Point. Although some people in Anchorage received the warning messages, officials clarified that the area was not under threat.
Local officials said that they wanted to be prepared for the worst-case scenario since it was difficult to ascertain the seriousness of a tsunami in the minutes after the seismic event. However, unlike a hurricane that can be seen forming days away from the shore, a tsunami wave is sudden and can be devastating to the shore on an immediate basis.
People in Kodiak at a High School after the Tsunami warning was issued on late Tuesday
Source: Larry LeDoux
In Kodiak, the local High School as well as the Catholic school provided refuge to evacuees. At Coast Guard base Kodiak, residents were instructed to head to Aviation Hill, high ground overlooking the nearby airport. At a time when congregations of large sizes are extremely unsafe due to the Covid-19 pandemic, evacuees were asked to wear masks throughout their stay.
Similar measures were taken in Unalaska by City Manager Erin Reinders. He activated the emergency operations center soon after feeling the tremors and notified the community to evacuate areas below 50 feet to higher ground, before later issuing the all-clear.
Kachemak Bay communities including Port Graham, Nanwalek, Seldovia, Homer and further inland up to the Fox River mudflats area were also given similar warnings, said Brenda Ahlberg, public information officer at the Kenai Peninsula Borough Office of Emergency Management.
According to Homer Deputy City Clerk and Deputy Public Information Officer Rachel Tussey, Homer residents were told to evacuate to the emergency operations center at the Homer Volunteer Fire Department. Homer High School was set up as an assembly point and emergency shelter.
Repeated flooding in coastal areas, debris-filled water that could injure people or weaken structures, and unusual current and wave activity that could affect coasts facing in different directions are some of the potential impacts that could be seen in days to come.
Experts said that earthquakes generating off the Alaskan shore can sometimes affect regions as far as Oregon and California, as was the case with the 9.2 magnitude quake in 1964. Paul Bodin, from the Pacific Northwest Seismic Network at the University of Washington, said that the frequent eruption of these Alaskan quakes helps scientists to look for signals before the next one strikes, thus giving them “predictive ability”.
The earthquake on Tuesday produced a roughly 10-inch wave recorded in Sand Point, which, according to seismologists was not enough indication of a tsunami. However, the Alaska Earthquake Center recorded “very strong shaking” in places such as Sand Point, Cold Bay and Perryville. The quake released “something like 15 times more energy than was released in the (magnitude 7.1) 2018 Anchorage earthquake,” according to Michael West.
Although the earthquake has caused little to no loss of life and property, it has generated interest among scientists as it seems to have occurred in a region that is not frequent on the earthquake radar despite the region’s high numbers of quakes. This region is known as the Shumagin Gap, near the Shumagin Islands and subduction zones around the area have long been ruptured. A subduction zone is formed when two tectonic plates meet along the southern coast of Alaska and pressure builds as the Pacific plate goes below the North American plate.
“There has been a vigorous debate about whether it is an area that is somehow immune from large earthquakes because the fault pressure is kind of constantly released instead of building up to a big earthquake,” said West.
Satellite images and other measurements will help scientists to determine whether this earthquake truly occurred in a zone earlier believed to be immune from earthquakes. The epicenter being underwater also makes assertions difficult at such an early stage. However, research in this area will definitely pick up speed post this event as it can help prepare for future similar occurrences.