If an Earthquake happens and we never know it, should we care?
The question assumes an earthquake could happen that wasn't reported. And the one comforting thing about earthquakes is, after they happen, they are given a number. We're immediately told how bad they were on the Richter scale. The Loma Prieta quake that interrupted the World Series in 1989 was a 6.9. The infamous San Francisco Quake of 1906 was a 7.9. Technically, there's no limit to how high the number goes. The highest ever recorded was a 9.5, which flattened cities in Chile in 1960. The seismic shock of that jolt was so big, tectonic plates were plunged deep into the mantle of the planet causing a 2.5 centimeter shift in the Earth's axis -- yes, the earthquake was so big, it altered the Earth's rotation. If anything qualifies as "the big one", that was it.
Most earthquakes are in the 2-3 point range on the scale. We get no warning they are coming. But we always get a full report after the fact. We get the number.
Except a study published this month (July 2025) reveals this is not true at all. Researchers from the US Geological Survey and the University of Columbia revealed a shocking fact: there are a significant number of earthquakes we never knew about at all. Until now.
The study was prompted by an upgrade to the seismic sensors around Yellowstone national park. The 3,400 square miles that make up Yellowstone are monitored non-stop by 60 permanent seismometers. Data from the sensors feed directly to University of Utah Seismograph Stations and are watched carefully by the U.S. Geological Survey.
If 60 seismometers seems like overkill, there's a very good reason the park is watched so carefully. Yellowstone sits on top of a super volcano. We've written previously about volcanos changing the planetary ecosystem. But a super volcano is much worse -- it's a Caldera System so powerful its eruptions can reshape continents.
A Caldera System is massive. It's an entire basin, a depression formed after ancient eruptions of magma formed a volcanic sinkhole. When the Caldera System erupts, an entire region fractures, with deadly super-hated gas and lava venting from the depths of the Earth for miles, collapsing the ground far as the eye can see. The one under Yellowstone is a staggering 45 miles wide. And it's erupted before -- about 640,00 years ago. When it did, all of North America was covered in ash.
So it's good we're monitoring things.
The new study, published in the journal Science Advances, used upgraded broadband stations that record a wider range of seismic signals, from tiny tremors to big quakes. Researchers wanted a better understanding of earthquake swarms, or clusters of small quakes. These swarms provide clues about underground changes in magma or fault stress. And they might help predict if and when the entire Caldera System might erupt.
As part of the study, researchers constructed a 15-year high-resolution earthquake catalog of the Yellowstone caldera region. To do this, they used a tool that hadn't existed before: AI. Leading-edge deep learning algorithms opened new doors, allowing a much richer, more accurate picture. AI can better tell what was a quake and what was just background noise. And these algorithms can give better insight into the timing and depth and location of quakes. Suddenly, seismic events that were small, or maybe overlapped others, could be logged. Even those that happened decades before.
They expected to uncover a few more events than they'd previously known about. But what they found was astounding. The study, called "Long-term dynamics of earthquake swarms in the Yellowstone caldera", cataloged over 86,276 previously undetected earthquakes under Yellowstone. That's a tenfold increase over the number of quakes we knew about.
Of course, it's great we know this now -- better late than never. All these tiny quakes can be symptoms of something larger building up, some serious event about to occur. Swarm patterns indicate magma movement, and offer early warning for volcanic eruptions or major earthquakes.
The Yellowstone Caldera will be better measured going forward.
The disturbing thing is, the Yellowstone Caldera is just one example. These calderas exist all over the world. We're standing on a sea of them. One of the largest is the 20-mile Long Valley Caldera in California. And it's still seismically active after 760,000 years of existing. But there are so many more. The Valles Caldera in New Mexico, Crater Lake in Oregon, Island Park in Idaho, Mount Saint Helens in Washington. And then, globally, these dangerous basins of volcanic potential are in Indonesia, Italy, Japan, New Zealand, Greece -- most of then are quiet now, but we have no idea how long this might last.
The Yellowstone study reveals we have been living on top of enormous seismic activity without realizing it. If these Calderas across the planet have been acting up in recent years, maybe building to a devastating eruption, we've been blind to it.
And if a Caldera does erupt, the consequences would be catastrophic. The blast zone would stretch 60 miles in every direction, destroyed by lava flow and deadly gas. Volcanic ash would blanket the country ten feet deep, especially near the source. We'd see global climate shock and a volcanic winter from ash blocking the sun.
It's good we're figuring out how to better monitor these things. Because if they do erupt, we won't survive to learn what number it hit on the scale.