California's Cascadia Earthquakes a Stark Reminder of Future Devastation

Earthquakes that have recently rumbled Northern California are stark reminders of stronger ones to come.

A 5.4 magnitude earthquake shook parts of Rio Dell in Humboldt County at 10.30 a.m on New Year's Day, the U.S. Geological Survey said. Half of the residents living in the area did not have power, and some were left without water.

There have been no reported injuries and officials have reassured residents that there are no subsequent risks linked to the earthquake, such as a tsunami.

The most recent earthquake came just two weeks after a magnitude 6.4 earthquake rattled the area on December 19. It caused widespread power outages, and at least two deaths.

Earthquakes are not unusual for the region as it is extremely tectonically active. The region is the most seismically active spot in the lower 48 states. But it is also long overdue for a catastrophic earthquake, which could result in a tsunami.

This is because it is located at the southern end of the Cascadia subduction zone—where the United States sits right over the ocean floor. The fault (a fracture or discontinuity in rock volume) lies at the northern tip of the San Andreas Fault, the border section between two massive tectonic plates under the Earth's surface.

These plates remain static, meaning they can see large pressures build up over time. When they do move, they can produce very large and destructive earthquakes. Earthquakes resulting from this fault could be as large as 8 or 9 on the Richter scale. Quakes on this scale can also trigger tsunamis. An earthquake and tsunami last happened in the Cascadia region on January 26, 1700, meaning a 'Big One' is long overdue.

The enormity of this potential event would be on par with the magnitude 9.1 earthquake and tsunami that hit Tōhoku, in Japan in 2011.

However, experts do not believe this most recent earthquake is a sign of something else to come just yet.

Alex Simms, professor at the Department of Earth Science at the University of California Santa Barbara told Newsweek: "This is normal, it is probably an aftershock or another earthquake on a fault nearby, but I don't think it is something else happening."

Since the earthquake on December 19, aftershocks have rippled throughout the region. They usually decrease in magnitude over time.

Harold Tobin, a professor and Paros Endowed Chair in Seismology and Geohazards at the University of Washington also told Newsweek that this earthquake is most likely an aftershock.

"Aftershocks are extremely common after most quakes," Tobin said.

When the first earthquake occurred on December 19, the U.S. Geological Survey estimated that there was a very small chance of aftershocks being a magnitude 5 or larger within the first week afterward.

While this recent earthquake was not a cause for concern, seismologists are still keeping a close eye on the Cascadia subduction fault.

"People in this region should always be prepared for a larger and more damaging earthquake and for a tsunami as well," Tobin previously told Newsweek. "We can forecast that there is a probability of earthquakes to come, but seismologists cannot yet predict an impending earthquake's time or location precisely, down to the year or decade, for example. We are actively researching whether there might be a telltale precursor we could detect, but we don't have one yet."

"We can measure signals that show us that the stress and strain are accumulating that will someday cause the next one—a magnitude 8 or 9 with a tsunami that crosses the entire Pacific as well as washing onto local shores."

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