Magnitude 4.5 Earthquake Hits North Coast Amid Ongoing Aftershock Sequence with Over 600 Quakes

The North Coast of California was rattled by a magnitude 4.5 earthquake, one of eight recent aftershocks in the region. This seismic activity follows the magnitude 7 earthquake that struck offshore in late 2024.

Lori Dengler, Professor Emeritus of Geology at Cal Poly Humboldt, provided insights into the ongoing aftershock sequence. She confirmed that the December 5 magnitude 7 earthquake moved a 35- to 40-mile section of the Mendocino Fault, causing several feet of displacement. Since then, the area has experienced over 600 aftershocks of magnitude 1 or greater.

Dengler explained that these smaller seismic events are a natural part of the fault adjusting to a new state of equilibrium following a major earthquake. While the recent magnitude 4.5 quake may have been widely felt, she reassured that this activity is not unusual.

According to the U.S. Geological Survey (USGS), there is a 50% chance of another magnitude 4 earthquake occurring within the next month and a 6% chance of a magnitude 5.

Dengler emphasized that the Mendocino Fault is the most seismically active in California, regularly producing magnitude 4 and larger earthquakes. While she does not anticipate an event exceeding the 1994 magnitude 7.2 earthquake in the near future, she cautioned that the threat of a catastrophic Cascadia Subduction Zone earthquake remains. A magnitude 9 Cascadia event could generate prolonged shaking and trigger tsunamis along the entire Pacific Northwest coastline.

Dengler urged residents to stay prepared and review the earthquake preparedness guide, “Living on Shaky Ground,“.