Could ShakeAlert get better after Humboldt’s earthquake alert?

At 8:10 a.m. Pacific time on June 24, a magnitude 5.6 earthquake struck about 11 kilometers north of Redwood Valley, and Humboldt phones got a ShakeAlert warning before the shaking arrived. The U.S. Geological Survey activated ShakeAlert for the quake, offering a few seconds of notice, not a guarantee of damage. For many people in Northern California, including some in Humboldt County, the warning sounded more urgent than the shaking they actually felt.

What the alert meant for Humboldt

For homes, schools, hospitals and coastal workplaces, the value of ShakeAlert is measured in the narrow gap between a phone vibrating and the ground starting to move. In a place like Humboldt County, that can mean enough time to brace, get off ladders, pause a lab procedure or prepare for a quick automated response from a building system. The Redwood Valley quake was in an area that could produce some damage, but impacts were expected to be relatively localized, which helps explain why the alert felt broad while the effects stayed uneven.

A warning that reaches far beyond the epicenter can look dramatic to people who feel little or no shaking, yet the same system may be lifesaving closer in, where every second matters more. Cal Poly Humboldt geology professor Eric Riggs said the system is not perfect, but that a few false positives are a better trade than no warning at all.

How ShakeAlert works today

ShakeAlert is the nation’s only public earthquake early warning system. The USGS says it currently serves more than 50 million residents and visitors in California, Oregon and Washington. The system is designed to give seconds to tens of seconds of warning before strong shaking arrives, which is not a lot of time, but is often enough to change what happens in a room, a hallway or a control center. The network watches seismographs for the first signals of an earthquake, sends the data to a processing center, and produces an estimate of the quake’s location, size and likely shaking intensity in a matter of seconds.

ShakeAlert can trigger actions such as slowing trains, opening fire station doors, closing water or gas valves and issuing public announcements. In schools and hospitals, those same few seconds can help staff move people away from immediate hazards and let systems react before the strongest shaking arrives.

Riggs pointed out that there is a narrow sweet spot between an alert that comes too early and one that lands after the shaking has already started. If Humboldt were closer to the epicenter, he said, phones might have sounded more urgently and with more direct warnings.

Where the next gains may come from

The most promising upgrade under study runs through ordinary internet infrastructure. Riggs is part of a team working with fiber-optic cable installed by Vero Fiber Network around Arcata, Willow Creek and Eureka. The cables carry light, and when seismic waves shake them, the light pulses change in ways computers can read. Because light moves faster than seismic waves, the system could potentially shave off precious seconds before a major quake hits.

In a December 2025 report, Cal Poly Humboldt detailed a fiber-optic project that used a distributed acoustic sensing interrogator and a tap test to examine earthquake detection. The report put the lower detection threshold at magnitude 1 and said the work built on an earlier pilot study using a small fiber line between Arcata and Eureka. The broader effort is tied to California’s Middle Mile broadband expansion program, linking earthquake science to the same physical infrastructure that expands internet access.

It is a multi-year, multi-agency effort led by the U.S. Geological Survey, Cal Poly Humboldt, Vero Fiber Network and state and local partners.

What residents should expect now, and what someday could look like

Right now, Humboldt residents should expect ShakeAlert to deliver brief warnings when the network can identify a real earthquake fast enough. It is useful in homes, schools, hospitals and utility systems, but it is still limited by distance, speed and the imperfect nature of real-world seismic data. A warning that arrives early enough to be useful in Eureka may not look the same in Redwood Valley, and a message that feels overcautious to one person may be exactly right for another.

Someday, fiber-optic detection could add a denser layer of coverage around Arcata, Willow Creek, Eureka and perhaps Trinidad, then stretch farther across the West Coast. That could mean more seconds in some cases, fewer blind spots in rural stretches and a better chance that the first alert matches the shaking that is actually coming.