For residents of Cordova, Alaska, the early morning shaking came without warning. At 03:32 UTC on Monday, a magnitude 5.3 earthquake struck 35 kilometers south-southwest of town. The U.S. Geological Survey recorded it at a shallow depth of 13.3 kilometers.
No tsunami warning was issued. Shallow quakes produce stronger shaking at the surface.
This one was shallow enough to fall into that category. At least 78 people reported feeling the event to the USGS. That number could grow as more accounts come in from the region.
The epicenter sat in open water, 35 kilometers from Cordova. That distance likely spared the community from worse effects.
But the USGS data shows no immediate reports of casualties or structural damage. The agency is monitoring for aftershocks, which are common after a quake of this size. Aftershocks can persist for days or even weeks, according to standard USGS guidance.
Alaska is no stranger to seismic activity. The area south of Cordova sits in a seismically active zone. Over the past two decades, at least 22 earthquakes of magnitude 5.0 or greater have been recorded within roughly 300 kilometers of the epicenter.
The strongest was a magnitude 7.1 earthquake in 2018. Monday’s quake registered as a moderate event.
Earthquakes in the magnitude 5 range are classified as moderate. They can cause minor to moderate damage near the epicenter. The shallow depth of 13.3 kilometers means the shaking was likely felt most strongly in communities closest to the epicenter.
Cordova is the nearest population center. The timing of the quake is worth noting.
It struck at 03:32 UTC, which translates to the early morning hours local time. Most residents would have been asleep. That may have influenced how many people felt the shaking and how they responded.
Seismologists classify shallow earthquakes as those occurring at depths less than 70 kilometers. The 13.3-kilometer depth of this event places it well within that range. Shallow quakes generate more intense ground motion than deeper ones of the same magnitude.
That is why a magnitude 5.3 quake at this depth can produce noticeable shaking over a wider area. The USGS detected the event through its real-time global seismic monitoring network.
That network allows for quick detection and analysis. The agency continues to monitor the region for any subsequent seismic activity. For now, the focus is on what comes next.
Aftershocks are a real possibility. The USGS advises people in affected areas to be prepared for further shaking.
That means securing heavy objects, knowing safe spots in buildings, and having an emergency kit ready. The 2018 magnitude 7.1 earthquake in the region serves as a reminder of what can happen. That quake caused significant damage and disruption.
Monday’s event was much smaller, but it shows the ground beneath Alaska remains active. No tsunami warning was issued. That is consistent with the characteristics of this quake.
Magnitude 5.3 earthquakes in shallow water typically do not generate tsunamis. The USGS would have issued a warning if the event posed a tsunami risk.
The 78 people who reported feeling the quake represent a fraction of the population in the region. Cordova has a population of roughly 2,500 people. The actual number of people who felt the shaking is likely higher.
The USGS relies on voluntary reports from the public to gauge the extent of shaking. Monday’s earthquake is a reminder that Alaska is one of the most seismically active regions in the world.
The state experiences thousands of earthquakes each year. Most are too small to feel. This one was not.
