Khaberni - A series of earthquakes struck Northern California on Thursday, renewing fears of a devastating earthquake within the next two decades with a 95% likelihood.
Intense seismic activity worries residents
According to the "Daily Mail", the US Geological Survey recorded dozens of small tremors in the Geysers area, which is less than 75 miles north of San Francisco.
The strongest of these tremors was a 4.2 magnitude on the Richter scale, occurring near the city of Cloverdale after 3 a.m. Eastern Time.
About 200 residents reported feeling the tremor, which affected as far as the San Francisco Bay and Palo Alto, more than 100 miles from the earthquake's epicenter.
Most reporters described the vibration as mild, and there were no reports of injuries or property damage.
12 aftershocks followed the main quake
Following the initial quake, 12 additional small tremors occurred in the geothermal field, which is situated on top of a network of seismic faults including the Bartlett Springs fault zone and the Healdsburg-Maakama fault system.
The area had experienced 26 earthquakes since Wednesday evening, forming an active earthquake swarm in this geothermal field that includes 18 power stations.
Scientific warnings of a possible disaster
In 2015, the US Geological Survey issued a report indicating a 95% likelihood of at least one earthquake with a magnitude greater than 6.7 occurring in the region by 2043, with this likelihood increasing to 72% specifically in the San Francisco Bay Area, home to about 8 million people.
Scientists identified three major faults that could cause this event: Hayward, Calaveras, and San Andreas. Despite the fame of the latter, which extends 800 miles, the report concluded that the Hayward and Calaveras faults carry a higher likelihood of rupturing in the next two decades.
Geological factors increase risks
Minor faults beneath the geothermal site make the area prone to frequent earthquakes, while experts noted that some tremors may result from geothermal energy extraction processes, where the surrounding rock contracts when steam and heat are extracted from underground reservoirs.
The process of re-injecting treated water back into the steam chambers adds additional pressure, as the thermal difference between the cold water and the extremely hot rocks creates instability in the underground environment.
The authority confirmed that the likelihood of an earthquake of magnitude 5 is possible, but larger earthquakes remain unlikely in the Geysers area given the lack of a known major connected fault, although the existing faults branch from the larger San Andreas Fault that runs through the San Francisco Bay.
