New research has uncovered previously unknown fault lines in the vicinity of Mt. Hood capable of producing an earthquake with potential for massive devastation. The fault networks are located to the north of Mt. Hood and extend to the Columbia River, near the Gate Creek and Blue Ridge Fault. They also extend to the south and southwest in the area surrounding Highway 26.
These Mount Hood faults are capable of producing a 7.2 magnitude quake. They were recently discovered by Ian Madin of the Oregon Department of Geology and Mineral Industries and Ashley Streig, an assistant professor of geology at Portland State University by new high-tech imaging known as light detection and ranging (LIDAR). LIDAR is a surveying method that measures distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a sensor. The team was able to later confirm the findings through field verification.
Scientist say that region experiences historical-strength earthquakes every 200 – 500 years or 246 years on average over the last 10,200 years. The last one occurring January 26, 1700, 318 years ago would mean the next is overdue. Ashley Streig explains how the earthquake that could result from these faults is different from the “Big One” the region has been preparing for:
“This would be a crustal earthquake as opposed to the Cascadia subduction zone earthquake Portland has been bracing for,” Streig said. “Subduction zone quakes are deeper below the surface, they last longer – as long as seven minutes – but they are lower in amplitude. The kind of quake we would get from Mt. Hood would be shorter – 20 seconds to less than a minute – and would be strong enough to knock you off your feet.”
While an earthquake along these fault lines would impose an immediate danger to the nearby cities, there is further concern of infrastructure damage that could impact a much greater reach. Hood River, Odell, Parkdale, White Salmon, Stevenson, Cascade Locks, Government Camp and the Villages at Mount Hood could experience significant shaking resulting in significant structural and infrustrucal damage. A strong enough earthquake in this area could even compromise rail lines and power lines that serve the surrounding areas including Portland. It would also have the potential to jeopardize dams, including the Bonneville Dam which is just downstream of the Gate Creek Fault. Dam failure could result in flooding or liquefaction of earth below low-lying elevation in Portland and beyond.
Steig continues to emphasize the concern and encourages those in the region to be diligent regarding awareness and preparation.
“Its not a matter of if it’s going to happen, it’s really when and which fault it will be,” stated Ashley Streig.