Though this week’s quakes have raised the concerns the so-called “big one” could be near, Tobin assured it is not necessarily the case. “Today’s quakes can be thought of as something like a main-shock and a swarm of aftershocks, the one distinction being that in this case, there’s not a lot of magnitude difference among them,” Tobin said. Lucy Jones, there have been more than 133 quakes of magnitude 5 or greater on the Blanco Fracture Zone since 1980 and have never been followed by something on land. This means there is NO tsunami risk because little water is displaced! /8reA3m3rL0- NWS Eureka December 8, 2021Īccording to seismologist Dr. Thankfully, they mostly occur far from shore along strike-slip faults. There has been a 'swarm' of earthquakes off the Oregon coast this evening the strongest reaching 5.8! “Blanco Fracture zone quakes are strike-slip (lateral motions of the crustal blocks on either side, rather than up-down displacement), so it is very unlikely for them to pose a tsunami threat, even if a bigger quake happened, like a magnitude 7.0 for example,” Tobin told CNN.

The fault is some 275 miles west of the Oregon coastline and about 200 miles west of the Cascadia Subduction Zone, where the largest and most destructive Northwest quakes have historically taken place. Though the epicenter of this week’s swarm of quakes, the Blanco Fracture Zone, is among the most seismically active in North America, it rarely leads to destructive quakes. This is not necessarily a precursor for the so-called ‘big one’ This fault can not only trigger devastating tsunamis but also destructive shaking. The quake occurred on the neighboring Cascadia Subduction Zone, a megathrust fault much closer to land, where the Juan de Fuca plate dives underneath the North American Plate. However, the activity has heightened the concern level for some, as the region is among the most earthquake-prone areas in North America and has already produced one of the largest quakes in the continental United States on January 26, 1700. When it comes to earthquakes, size matters but so does the terrainįortunately, according to the US National Tsunami Warning Center, none of this week’s quakes have triggered a tsunami alert.

Credit: USGS / Ben Brooks Ben Brooks/USGS/JPL/NASA A USGS Earthquake Science Center Mobile Laser Scanning truck scans the surface rupture near the zone of maximum surface displacement of the magnitude 7.1 earthquake that struck the Ridgecrest area.

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