The fault line near Oregon’s coast has recorded several earthquakes within a span of less than 12 hours, raising concerns about the possibility of a significant seismic event.

The US Geological Survey (USGS) tracked the most recent quake, measuring 5.1 in magnitude, at 1:00pm local time on Tuesday. This marks nearly a dozen quakes registering above 2.5 magnitude.

The seismic activity began late Monday when a 5.8 magnitude tremor hit, triggering aftershocks throughout Tuesday.

The location of the epicenter is approximately 102 miles west-southwest of Port Orford, Oregon. This area is part of the Cascadia Subduction Zone, where the Juan de Fuca Plate descends beneath the North American Plate.

This fault system produces frequent small offshore tremors and carries the risk of massive, destructive earthquakes. 

Scientists have long warned that the zone is overdue for a catastrophic event, with many nicknaming it the ‘Sleeping Giant.’ 

The fault is capable of a magnitude 9 earthquake that would impact most of the northwestern US Coast, including Seattle and Portland. 

Northern California has also experienced increased seismic activity on Tuesday, with the USGS detecting about half a dozen tremors above 2.5 magnitude.

In April, researchers at Virginia Tech found that an 8.0 magnitude or higher quake along the Cascadia Subduction Zone, combined with rising sea levels, would cause coastal land to sink up to 6.5 feet within 30 minutes of a major tremor.

They determined that an earthquake of magnitude 8.0 or higher, combined with rising sea levels, could cause coastal land to sink up to 6.5 feet within 30 minutes.

The most severe effects would hit southern Washington, northern Oregon and northern California, some of the region’s most densely populated areas.

This event would result in a significant expansion of the coastal floodplain, an area with a one percent chance of flooding each year, increasing it from 35 square miles to 116.

Such an event would expand the coastal floodplain from 35 to 116 square miles, placing an additional 14,350 residents, 22,500 structures, and 777 miles of roadway at risk.

The Cascadia Subduction Zone has historically produced quakes of magnitude 8.0 or larger every 400 to 600 years, with the last one striking in 1700.

Against this backdrop, Oregon Gov. Tina Kotek on Monday announced new seismic safety rules, just hours before the 5.8 magnitude quake hit.

Kotek’s order requires all new state-owned buildings larger than 10,000 square feet to meet the strictest earthquake standards, while older structures must be upgraded to current life-safety codes by 2060.

‘Preparing for an earthquake is a long game,’ Kotek said. ‘If we look at 50 years, we can spread that cost out—replace or retrofit two per cent of our buildings each year, and in 50 years we’ll have upgraded every single one.

‘Yes, it’s a multibillion-dollar effort, but planning it over decades makes the funding challenge more manageable.’

State Rep. Dacia Grayber, a first responder and earthquake-readiness advocate, said, ‘One of the things that keeps me up at night is … we are the only post-industrial region pretty much in the world that hasn’t lived through our worst natural disaster.

‘We’ve seen this train barreling down on us, yet we only react when emergencies start to personally affect us.’