Over a million Americans in the northeastern US could be at risk of a tsunami due to a newly discovered fault line.
Scientists have found an approximately 45-mile-long fracture in the Earth that runs through British Columbia in Canada and escaped detection for thousands of years.
Experts suspect that because of the layout of the fault it could spark a large earthquake in Canada.
The quake’s effects could generate a tsunami in the area around the Georgia Basin, which could hit parts of Washington, as well as British Columbia.
The discovery was made by a team that included Nick Harrichhausen, a postdoctoral researcher at the Université Grenoble Alpes in France.
If an earthquake at this newly discovered fault line pushes up the seafloor of Haro Strait, it could displace enough water to cause a tsunami in the surrounding Georgia Basin
A tsunami can follow an earthquake, even if the geological event only pushes the land upward a few meters
Harrichhausen and his colleagues found that the fault’s two massive rock blocks slipped against each other and generated a major earthquake several thousand years ago.
He told DailyMail.com it’s possible this could happen again.
In fact, because of the Pacific Northwest’s numerous geological fault lines – not just the newly discovered one – he encourages people to stay prepared for a possible earthquake by keeping several days worth of food, water, medicine, and emergency supplies.
Named the XEOLXELEK-Elk Lake Fault (XELF for short), the geological intersection runs diagonally across the Saanich Peninsula north of Victoria from the northwest to the southeast.
The reason for its possible destruction, Harrichhausen said, is that the XELF is what’s known as a ‘dip-slip’ fault, where two blocks of rock move up-and-down art their point of contact, as opposed to side-to-side.
‘Because we document dip-slip, which produced vertical offset of the Earth’s surface, and the fact this this fault would likely rupture underwater, there is potential an earthquake on this fault would produce a local tsunami in the Georgia Basin,’ said Harrichhausen.
The Georgia Basin encompasses the cities of Bellingham, Seattle, Tacoma, and Olympia in the US, and Vancouver, Victoria, and Whistler in Canada.
‘Given the XEOLXELEK-Elk Lake fault hosted an earthquake within the Holocene (last 12,000 years), we have to consider that it is active and that it could host another earthquake of a similar magnitude (or lesser) to the one we observe in our study,’ he said.
This ancient quake, with a magnitude of 6.1 to 7.6 on the Richter scale, rocked the region along this fault line between 4,700 and 2,300 years ago, Harrichhausen and his colleagues found.
For comparison, an M 6 earthquake has the power equivalent to 60 million kilograms of TNT, and an M 7 packs the power of 20 billion kilograms.
‘An earthquake of these magnitudes would be damaging, especially given its proximity to urban areas,’ Harrichhausen said. ‘In terms of a timeline it is not possible to predict when the next earthquake will be.’
Not only could it rock the 400,000+ people in the immediate vicinity of the fault, but it could create a tsunami in the larger region, he explained.
‘This particular fault certainly has implications for people in the US as we map it to possibly connect underneath the Haro Strait and the US border to the Devils Mountain fault in Washington State,’ said Harrichhausen.
‘Thus a rupture could extend to the United States, and even if it didn’t, a large earthquake on the XEOLXELEK-Elk Lake would be felt by people in the northern Puget Sound area.’
Calculating when an event like this could occur is challenging, though, even for geologists.
‘The only thing we can do is look at the past earthquake recurrence interval (the average number of years between earthquakes),’ he said.
And the new study is limited in making this calculation because it requires at least two separate earthquakes to estimate the time between ruptures.
‘Also, keep in mind this is a very rough calculation because the times between earthquakes can vary hugely,’ he added. ‘Therefore, more studies could allow us to better understand the hazard the fault poses.’
Harrichausen and his colleagues explored the fault line by digging a trench across it, enabling them to search for signs of earthquakes and fault line shifts in the geological history.
These signs came in the form of magnetic field changes.
Minerals in the rocks have different levels of magnetism, so measuring these differences can show whether large rock formations formed at the same time and stayed in shape, or whether they were broken up.
What they found was that, sometime after glaciers had carved the landscape, the slip-dip fault had shifted the land.
They calculated this to be sometime within the last 12,000 years, likely within the window between 4,700 and 2,300 years ago.
The study appeared this week in the journal Tectonics.
If another quake does occur, Harrichhausen said, people in the region can take some basic steps to prepare.
‘Earthquake preparedness experts suggest that people secure large furniture and appliances, create a disaster plan, organize disaster supplies for at least 3 days and up to 2 weeks of self-reliance (food, water, medicine, etc.), and take steps to minimize financial hardship,’ he said.
‘Of course, when an earthquake begins, you should DROP, COVER, and HOLD ON.’