A series of small earthquakes rumbled across Humboldt County and the surrounding region over the weekend and into today as more than a dozen temblors were recorded by the U.S. Geological Survey with the largest recorded at 4.5 magnitude on Sunday afternoon.
The earthquake swarm, described as a “group of small to light earthquakes of roughly the same magnitude clustered in time and space in a small area,” began on Friday afternoon and the shocks were still being felt this morning when a sharp 3.2 magnitude earthquake rattled downtown Eureka.
The earthquakes served as yet another reminder to local residents that we live in a seismically active region and that preparedness is of paramount importance.
“Sheriff’s OES recommends that all Humboldt County residents work toward a goal of two weeks of disaster supplies for your family, including a gallon of water per person per day, non-perishable food, and extra water and food for pets,” said Dori Lanni, Emergency Services Manager for the Humboldt County Office of Emergency Services. “We recommend that residents in remote areas maintain supplies for more than two weeks. Following a countywide disaster, rural communities may be inaccessible while roads and bridges are inspected and repaired. Following a major earthquake, we can expect a long series of aftershocks that can cause additional damages and require multiple inspections.”
The quakes were centered around an area called the Mendocino Triple Junction where the Gorda, Pacific and North American plates, along with the San Andreas fault, the Mendocino fault and the Cascadia Subduction Zone fault system all meet.
According to information provided by Lori Dengler, emeritus professor of geology at Humboldt State University, the small quakes could continue over the course of the next few days. Dengler also said we are overdue for a larger magnitude quake that can cause damage.
“What we know is we have had a long, an unusually long quiet spell on the North Coast, so if you look at the earthquake activity we haven’t had a whole lot since 2010,” Dengler said. “There was one earthquake offshore that wasn’t felt strongly and Jan. 9, 2010, was our last strong earthquake. If you look at all the earthquakes since the turn of the century, on average we have an earthquake that will cause damage every seven years.”
The latest swarm might not have caused any damage but it did serve as a reminder that an earthquake can strike at any time. As Dengler pointed out, we don’t have a crystal ball to see into the future when a larger quake that causes damage will strike.
“When people ask me what do those earthquakes mean, most likely the 4.5 is the largest we will get in that sequence,” she said, adding, “Would I be surprised with a (magnitude) 5 or 6? No, I would not be surprised and we should take this as a reminder we live in earthquake country. Yes, we will have a damaging earthquake and we are one day closer to that event today than we were yesterday.”
Lanni reiterated the need to be aware of the dangers, the need to be prepared and reminded residents the county alert system is available.
“Residents can register cell phones for text and voice messages, landlines, and email addresses, to receive information about emergencies affecting multiple locations, like your home, your workplace, and children’s schools,” Lanni said. “It just takes a couple of minutes to sign up at http://humboldtgov.org/alerts.”
Dan Squier can be reached at 707-441-0528.
