Several strong aftershocks measuring 4.0 or greater have been reported following a magnitude-7.0 earthquake that struck off the coast of Northern California on Thursday. Notably, the strongest aftershock reached a magnitude of 4.7 just two minutes after the initial quake occurred at 10:44 a.m., impacting areas along the California coast and some inland regions.
Residents in San Francisco, approximately 270 miles away from the epicenter near Ferndale in Humboldt County, experienced noticeable rolling movements during the quake. In total, millions of Californians found themselves under a tsunami warning that affected coastal areas from Oregon to the Bay Area. Fortunately, this alert was lifted relatively quickly after scientists determined that the undersea earthquake was unlikely to result in significant coastal flooding.
Reports indicate that minor damages were sustained, including broken windows and ruptured water pipes, with some items falling from store shelves. The US Geological Survey identified nearly 200 aftershocks in the hours following the main event, with at least nine measuring 4.0 or higher. The region is known for its seismic activity due to the convergence of three tectonic plates.
Seismologist Robert DeGroot emphasized the importance of preparedness for earthquakes of this nature, as they do not occur frequently but are common enough to warrant caution. The previous notable seismic event in the region was a magnitude-6.4 earthquake in 2022, which significantly affected local infrastructure.
The type of earthquake experienced on Thursday was classified as a strike-slip, which typically causes horizontal shifts rather than vertical displacement, making the occurrence of a tsunami less likely. Dr. Lucy Jones explained that this type of quake primarily moves land sideways and does not usually displace significant amounts of water.
As aftershocks can persist for varying durations, the USGS has put forth forecasts to help residents stay informed and prepared for ongoing seismic activity in this dynamic area.
In summary, while Thursday’s earthquake has caused some disruption, the quick response from emergency services and the timely lifting of the tsunami warning have helped mitigate potential risks. It serves as a reminder for the communities in seismically active regions to remain vigilant and prepared for future seismic events.