An earthquake with a magnitude of 3.9 near the San Francisco region made federal scientists monitor it
TOI GLOBAL DESK | TOI GLOBAL | Nov 27, 2025, 02:06 IST
A 3.9 magnitude quake hit the Geysers area, which is situated north of San Francisco, early Monday. As a consequence, scientists from the federal government continue to examine the region for aftershocks and their impacts.
TL;DR
As per the permissions granted by the local authorities, there has been no damage report caused by the earthquake that shook the area north of San Francisco. While updating local seismic data, scientists from the U.S.G.S. convey that they are watching closely for potential aftershocks in the area.
A minor earthquake, estimated at a magnitude of 3.9, has caused some damage to an area in San Francisco, as per the information given by the United States Geological Survey. The shock had been felt in the most silent hours of the 4th of July, and its occurrence time was 7:08 a.m. local time. The location of the seismic event was basically a rough estimation of an area that is approximately one mile northwest of The Geysers, California. The USGS at first had recorded the event as a 4.1 magnitude earthquake, and after the standard recalibration of the seismologists, they changed the magnitude later.
The U.S.G.S. workers credited the disturbance as being very faint, thus in line with the areas that reported a shake intensity level of 3 and over. However, the officials stated that although the agency’s maps illustrate the calculated shaking, people living outside the surveyed areas might also feel the quake. The intensity scale is an indicator of the amount of ground motion and not the earthquake's magnitude, remarked Jessica Turner, a U.S.G.S. seismologist, in an email statement.
Local emergency services arranged for the confirmation of the absence of human casualties. The Emergency Management Office in Sonoma County has reported that it has received numerous calls from residents expressing their experience of light shaking while none have reported any structural damage. "Such an event reminds us that seismic activity is still a threat to the communities of Northern California," the office remarked.
After the main earthquake, aftershock activities are predicted in the surrounding area, which is not only a hotspot of the Earth's heat release but also seismic activities in California. The aftershocks usually come in the wake of the initial rupture and may remain for a while and even years in some cases. Although most of them have smaller magnitudes, the U.S.G.S. scientists warn about the possibility of some aftershocks having magnitudes as high as or even higher than that of the main quake. Turner added that the subsequent events are the Earth's crust becoming accustomed to the stress changes resulting from the initial slip along the fault.
U.S.G.S. is going to keep updating the shake intensity maps as they gather more data including the reports collected via its Did You Feel It program, the agency announced. Besides, it employs sensor networks and satellite-based systems to monitor seismic patterns within 100 miles from the epicenter for at least one week after an event. The aim of this data is to make predictions more precise and to help with the planning of emergency preparedness in regions prone to earthquakes.
The experts attribute the recent report from The California Geological Survey which stresses the importance of easy public access to prompt earthquake information as the main factor for readiness and resiliency in the affected communities. Improvements in seismic mapping and remote sensing are, in fact, the main sources of their becoming more accurate in assessing the activity.
During the situational review, it was still the recommendations of the federal and state agencies that people living in the impacted areas should make proper preparations for emergencies and keep themselves informed through official sources. This unfortunate event is just one more time to remember that it is necessary to be very cautious in a place that is known to have small tremors regularly.
FAQs
As per the permissions granted by the local authorities, there has been no damage report caused by the earthquake that shook the area north of San Francisco. While updating local seismic data, scientists from the U.S.G.S. convey that they are watching closely for potential aftershocks in the area.
A minor earthquake, estimated at a magnitude of 3.9, has caused some damage to an area in San Francisco, as per the information given by the United States Geological Survey. The shock had been felt in the most silent hours of the 4th of July, and its occurrence time was 7:08 a.m. local time. The location of the seismic event was basically a rough estimation of an area that is approximately one mile northwest of The Geysers, California. The USGS at first had recorded the event as a 4.1 magnitude earthquake, and after the standard recalibration of the seismologists, they changed the magnitude later.
The U.S.G.S. workers credited the disturbance as being very faint, thus in line with the areas that reported a shake intensity level of 3 and over. However, the officials stated that although the agency’s maps illustrate the calculated shaking, people living outside the surveyed areas might also feel the quake. The intensity scale is an indicator of the amount of ground motion and not the earthquake's magnitude, remarked Jessica Turner, a U.S.G.S. seismologist, in an email statement.
Local emergency services arranged for the confirmation of the absence of human casualties. The Emergency Management Office in Sonoma County has reported that it has received numerous calls from residents expressing their experience of light shaking while none have reported any structural damage. "Such an event reminds us that seismic activity is still a threat to the communities of Northern California," the office remarked.
After the main earthquake, aftershock activities are predicted in the surrounding area, which is not only a hotspot of the Earth's heat release but also seismic activities in California. The aftershocks usually come in the wake of the initial rupture and may remain for a while and even years in some cases. Although most of them have smaller magnitudes, the U.S.G.S. scientists warn about the possibility of some aftershocks having magnitudes as high as or even higher than that of the main quake. Turner added that the subsequent events are the Earth's crust becoming accustomed to the stress changes resulting from the initial slip along the fault.
U.S.G.S. is going to keep updating the shake intensity maps as they gather more data including the reports collected via its Did You Feel It program, the agency announced. Besides, it employs sensor networks and satellite-based systems to monitor seismic patterns within 100 miles from the epicenter for at least one week after an event. The aim of this data is to make predictions more precise and to help with the planning of emergency preparedness in regions prone to earthquakes.
The experts attribute the recent report from The California Geological Survey which stresses the importance of easy public access to prompt earthquake information as the main factor for readiness and resiliency in the affected communities. Improvements in seismic mapping and remote sensing are, in fact, the main sources of their becoming more accurate in assessing the activity.
During the situational review, it was still the recommendations of the federal and state agencies that people living in the impacted areas should make proper preparations for emergencies and keep themselves informed through official sources. This unfortunate event is just one more time to remember that it is necessary to be very cautious in a place that is known to have small tremors regularly.
FAQs
- Are aftershocks expected?
Certainly, and U.S.G.S. scientists will be monitoring the area for a few days. Their expectation is the occurrence of aftershocks as well. - What method does U.S.G.S. use to define shaking intensity?
The scale for shaking intensity is an indication of the physical changes in the ground rather than the magnitude. In this particular case, the earthquake resulted in only minimal intensity levels.