A software bug’s seismic error
An alert of a 6.8 quake is tied to data from 1925.
Remember Y2K, that hyped computer bug and harbinger of digital apocalypse that never happened when the year 2000 arrived?
Well, 17 years later, it appears something like a Y2K bug played a role in a mistaken alert sent out Wednesday about a magnitude 6.8 earthquake off the Santa Barbara coast — back in 1925.
The error happened when someone at Caltech tried to correct the exact location recorded for the Prohibition-era Santa Barbara earthquake, which happened 92 years ago.
The erroneous report was issued around 4:49 p.m., according to the U.S. Geological Survey, and began arriving in quake-trackers’ email in-boxes around 4:51 p.m.
A closer look at the alert, however, would have shown that something was amiss. The time of the alert was dated June 29, 2025, at 7:42 a.m. But it corresponds with a real earthquake that occurred a century earlier.
The false alert also did not show up on the USGS website that maps new earthquakes.
“That’s a mistake. It’s not real,” said Caltech seismologist Egill Hauksson.
He said that a seismologist at UC Santa Barbara had recently complained to the USGS National Earthquake Information Center that the precise location of Santa Barbara’s 1925 earthquake was not correct and about 6 miles off from where records actually indicated.
Hauksson’s team was asked by the National Earthquake Information Center to update the location of the historic event in the Advanced National Seismic System database. Someone on Hauksson’s team did so. If everything had gone right, almost no one should have noticed the change.
The USGS Web pages were updated correctly. But in the USGS email notification system, the year got changed from 1925 to 2025, which caused an email to be sent from the server that typically distributes alerts of new earthquakes.
“Apparently, there is a software bug around somewhere,” a summary of the incident provided by Hauksson said.
The bug was related to something called “Unix epoch time,” which starts in 1970, Hauksson said in an email. “The year of 1925 wrapped around in the software and became 2025,” he said.
In a statement posted on Twitter, the USGS said the revision of the 1925 earthquake was “misinterpreted by software as a current event. We are working to resolve the issue.”
As to whether an earthquake off the Santa Barbara coast of that magnitude would have been felt in downtown L.A., Hauksson said: “Yes, it would have been very lightly felt. Particularly, people in highrises would have felt swaying back and forth for a while.”
If the quake had just occurred, the L.A. area would have felt the shaking before the USGS alert arrived in local email boxes, Hauksson said.
For instance, Pasadena, which is about 96 miles from the epicenter of the 1925 Santa Barbara earthquake, would be expected to feel shaking about 40 seconds after the earthquake would have begun in the Santa Barbara Channel — fast enough to outpace the existing USGS email alert system.
The expected intensity in Pasadena for a magnitude 6.8 quake that originated 96 miles away would be a 3.3 on the Modified Mercalli Intensity scale.
Here is what intensity 3 and intensity 4 quakes feel like, according to the USGS:
Intensity 3: “Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck.”
Intensity 4: “Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.”