Thanksgiving Morning Rattled by Earthquake Swarm
Residents across Northern California were given an unexpected and unsettling wake-up call on Thanksgiving morning, as a series of earthquakes shook the region. The seismic activity began in the early hours and was centred near The Geysers geothermal field, a known hotspot for such events.
Details of the Seismic Event
The sequence commenced at approximately 4:30 am Pacific Time (7:30 am ET), with the US Geological Survey reporting a total of at least 13 distinct tremors. The magnitudes of these quakes varied significantly, ranging from a minor 1.0 to a more noticeable 3.7. The initial event, a 3.6 magnitude tremor, was powerful enough to be felt by residents as far south as San Francisco. The swarm continued for over an hour, with the final recorded quake, a small 1.1 magnitude event, detected at 5:47 am PT (8:47 am ET).
A Region Prone to Seismic Activity
The location of this earthquake swarm is no coincidence. The Geysers is a vast geothermal field situated in the Mayacamas Mountains, spanning Sonoma, Lake and Mendocino counties. This area harnesses underground steam for electricity generation. Despite its name, given by early settlers who misunderstood the natural features, the area does not have true geysers but is instead characterised by steam vents known as fumaroles.
Critically, this part of northern California sits atop a complex network of faults, including the Bartlett Springs Fault Zone and the Healdsburg-Maacama Fault system. The presence of numerous smaller faults directly beneath the geothermal site makes the area particularly prone to frequent earthquakes. Seismologists have noted that some of this seismic activity may be triggered by the region's extensive geothermal energy operations, a fact that raises ongoing concerns about the potential for stronger shaking in the future.
This is a developing story. Further updates are expected as more information becomes available.
