Mount Rainier Just Shook Hundreds of Times. Here’s What That Means for Seattle and the Pacific Northwest

Image courtesy of the U.S. Geological Survey (USGS). Source: www.usgs.gov

If you're in Seattle or anywhere in the Pacific Northwest, this week's cluster of earthquakes under Mount Rainier should be on your radar.

Starting early Tuesday morning, scientists at the U.S. Geological Survey and the University of Washington recorded a rapid burst of seismic activity beneath the iconic volcano. In just a few hours, more than a year's worth of small earthquakes occurred deep below Mount Rainier. While none were strong enough to be felt at the surface, this "earthquake swarm" serves as a powerful reminder: the ground in our region is constantly shifting.

Whether you live in Seattle, Tacoma, Olympia, or nearby, this event is a clear signal that we all need to be thinking about earthquake preparedness in the Pacific Northwest.

What Happened Beneath Mount Rainier?

According to the Pacific Northwest Seismic Network and the Cascades Volcano Observatory, the swarm began just after 1:30 a.m. on July 8. Over the next several hours, scientists recorded hundreds of small earthquakes beneath Mount Rainier. The largest had a magnitude of 1.7, with most occurring between 1.2 and 3.7 miles beneath the surface.

Experts emphasize that this is one of the largest earthquake swarms seen at Mount Rainier in recent years. While it does not suggest an eruption is likely, it confirms that the volcano and surrounding areas are seismically active and need to be closely monitored.

What Are Earthquake Swarms?

An earthquake swarm is a series of small tremors that occur over a short period of time. Unlike a typical sequence of aftershocks, swarms do not follow a single major event. Instead, they involve multiple quakes of similar size, clustered together. These swarms can be caused by volcanic activity, tectonic shifts, or a combination of both.

In the Pacific Northwest, where major fault systems meet an active volcano, earthquake swarms are an important warning sign. They show us that movement is happening underground, and while these smaller events may not cause damage, they remind us that larger earthquakes are always a possibility.

Should Seattle Be Concerned?

Yes, and for good reason. Mount Rainier sits about 60 miles southeast of Seattle, but seismic and volcanic activity in that region can have far-reaching effects. More importantly, the Seattle area is directly threatened by local fault lines like the Seattle Fault Zone and the Cascadia Subduction Zone. These systems are capable of producing large, damaging earthquakes that could impact everything from infrastructure to personal safety.

This week’s Mount Rainier earthquake swarm adds to growing evidence that our region remains active. Whether you live in a downtown apartment, a single-family home, or manage a commercial building, it’s essential to understand the risks and take steps to be prepared.

Why Older Buildings Are Especially at Risk

Many homes and buildings in Seattle and surrounding communities were built before modern seismic building codes existed. Structures built before 1980 often lack the anchors and reinforcements needed to withstand lateral movement caused by earthquakes. This means that even moderate shaking could cause serious structural damage.

If your building shakes during small earthquakes, has never been inspected for seismic safety, or shows signs like cracks in the foundation or walls, it may be vulnerable. Homes with large open garages or “soft” ground floors, buildings located on slopes, and those with crawl spaces or cripple walls are especially at risk. Even if everything appears fine on the surface, the structure underneath may be unprepared for the stress of an earthquake.

At Seattle Seismic, we’ve worked with people across the region, not just homeowners, but also renters, business owners, and property managers, to evaluate and strengthen buildings so they can better withstand the next big shake.

What Is Seismic Retrofitting and Why Does It Matter?

A seismic retrofit is a set of upgrades designed to make your home or building more resistant to earthquake damage. It does not require a major remodel or a full rebuild. Most residential home retrofits can be completed in a week.

The process typically involves bolting the building’s frame to its foundation, reinforcing the structure with plywood shear panels, and securing or replacing heavy features like chimneys. These modifications reduce the risk of structural failure and can save thousands of dollars in repairs, not to mention help keep people safe.

Retrofitting is a smart, proactive step, especially in a region like Seattle, where the risk of a major quake is real and growing.

What Can You Do Right Now?

Seattle Seismic is currently offering free seismic evaluations for residents and property owners throughout the greater Seattle area. If you’re not sure whether your home or building is earthquake-ready, this is the perfect opportunity to find out. There’s no cost, no pressure, and no guessing. Just real information that helps you make informed decisions about your safety.

This week's Mount Rainier earthquake swarm may not lead to an eruption, but it highlights a bigger truth: Seattle and the Pacific Northwest are sitting on a very active fault system. The question is not if a larger earthquake will occur, but when.

Preparedness starts with awareness. If you live, work, or spend time in this region, now is the time to act.

Call (206) 800-6417 to book your free seismic evaluation today.