Powerful earthquakes strike, and energy surges through rock and soil in waves, much like ripples spreading across a pond after you toss a stone. Unlike the fleeting ripples in a pond, seismic waves travel deep within Earth’s crust, mantle, and core, looping back to the surface over and over again.

Major quakes, especially those with a magnitude of 9 or higher, pack so much energy into the Earth that they trigger oscillations that can last days or even weeks. Imagine the planet stretching and compressing, then slowly relaxing again in steady, rhythmic pulses. Jonathan Snively of Embry-Riddle Aeronautical University explains, “These waves start as brief packets, but they form into narrow, focused bands, indicating a natural resonance or ringing that persists. This ringing can last for hours, and it’s easily detectable.”

Unlike the usual hum of tides, wind, or distant traffic, this ringing stands out sharply, impossible to ignore. Snively’s team measures these vibrations at frequencies tied to the planet’s size, shape, and internal composition—almost like a unique fingerprint for Earth’s structure. These patterns provide crucial clues about Earth’s deep layers, areas we can’t explore with shovels or drills. In fact, the work done on seismic waves from quakes like those in Alaska during the 1960s helped launch global efforts to map these vibrations, proving that the ground beneath our feet has a lot to say if we listen closely.

How Earth’s Vibrations Reveal Its Secrets

When Earth rings after a quake, don’t expect a melody you’d hum along to. Specialized tools, such as seismometers and gravity meters, track rhythmic jolts as energy waves move through the planet’s layers. Major quakes have enough force to shift massive slabs of rock and entire oceans. Subduction zone quakes, where one tectonic plate slides under another, cause the crust to lurch dozens of feet in the blink of an eye. These brutal shifts send acoustic shock waves soaring upward and seismic waves deep below, shaking everything from bedrock to the air.

These waves travel through the crust, mantle, outer core, and inner core, bouncing off boundaries where density or composition changes. Some waves ricochet off layers like a ball bouncing off a wall, while others twist and bend, creating interference patterns. A few waves are tough enough to loop around the globe multiple times, amplifying certain frequencies and muting others. Matt Zettergren, a researcher at Embry-Riddle, notes how these seismic waves stir up chaos in the ionosphere—where auroras shine—by knocking out electrons. These disturbances can mess with radio signals and glitch GPS systems, tying Earth’s shakes to everyday technology. Rocket launches and nuclear tests also create similar disruptions, proving how noisy our planet can be when stirred up.

Shockwaves Travel Through the Planet

Earth rings after a quake, but don’t expect a tune you’d hum along to. Specialized tools—think seismometers or gravity meters—pick up rhythmic jolts as energy waves pulse through the planet’s body. Major quakes pack enough punch to shove giant slabs of rock and oceans sideways. Subduction zone quakes—where one tectonic plate rams under another—see the crust lurch dozens of feet in a heartbeat. Those brutal shifts launch acoustic shock waves skyward and seismic waves deep underground, shaking everything from bedrock to air.  

Waves tear through crust, mantle, outer core, and inner core, slamming into spots where density or makeup shifts. Some bounce off layer edges like a ball off a wall; others twist and bend, weaving messy interference patterns. A few hardy ones loop the globe multiple times, amping up certain frequencies while drowning out others. Matt Zettergren, another Embry-Riddle researcher, flags how these waves spark chemical chaos up high, carving “holes” in the ionosphere—that charged zone where auroras glow—by knocking out electrons. Those sky scars scramble radio signals sailors rely on and glitch GPS maps drivers swear by, tying Earth’s shakes to our everyday tech. Rocket launches or nuke tests pull the same stunt, proving the planet’s a noisy place when riled up.

How We Hear the Earth Ring

Scientists use advanced ground-based equipment to listen in on the planet’s vibrations. Seismic observatories around the world capture wave patterns, allowing us to monitor shifts from Alaska to Australia. Meanwhile, gravity meters, like one stationed in a fireproof basement in Canberra, detect even the smallest changes in Earth’s gravitational pull. GPS satellites also help track fluctuations in the ionosphere—the charged region above Earth—identifying any disturbances caused by seismic events.

Through these collaborative efforts, researchers share real-time data, working together to decode Earth’s mysterious sounds. The Greenland “unidentified seismic object” incident, for example, was investigated with the help of modern tools and chat apps that allowed scientists across the globe to piece together the event. From remote mountain ranges to high-tech satellites orbiting in space, we now have the ability to hear and understand every shift within our planet.

When the Ringing Made Headlines  

Massive events don’t just shake the ground—they grab attention worldwide, leaving scientists scrambling to decode Earth’s vibrations. Each case highlights how the planet hums, from violent quakes to sneaky landslides. Here’s how three standout moments turned heads and tuned us into Earth’s ringing.  

Alaska’s Big One (1964)

On March 27, 1964, a cataclysmic event unfolded as a colossal 9.2 magnitude earthquake—the mightiest tremor ever recorded in North America—shook the very foundations of Alaska’s Prince William Sound. For a relentless four minutes, the earth roared violently, fracturing roads and rending the ground wide open. Eyewitnesses described a chilling sound, likening it to a ferocious beast gnawing on gravel beneath their feet. In the aftermath, scientists would reveal that the quake caused the planet to “ring like a bell,” with seismic waves reverberating all the way to Seattle’s iconic Space Needle, a staggering 1,200 miles to the south. In Anchorage, the unforgiving shaking turned calm kitchens into a scene of chaos as dinner plates danced and rattled, as if possessed by the tremors that seemed to stretch on longer than most quakes dared to.

In the wake of this natural disaster, tsunamis surged with terrifying speed, engulfing the small town of Chenega and obliterating Valdez, leaving nothing but destruction in their wake. Landslides cascaded down, burying the heart of Anchorage’s business district beneath a suffocating blanket of nine feet of debris. Meanwhile, in Turnagain Heights, the once-steadfast soil morphed into a quagmire, swallowing entire houses as if they were mere toys. The coastline shifted dramatically, sinking by as much as eight feet in certain areas while others bucked up by a staggering 38 feet, drowning lush forests in a deluge of saltwater.  

As night fell, a monstrous 200-foot wave viciously dismantled Valdez’s port, igniting catastrophic oil fires that illuminated the darkened sky like a hellish beacon. The tremor claimed 131 lives—15 lost to the shaking itself, while the majority fell victim to the tumultuous waves and landslides. This monumental earthquake not only wrought havoc but also fundamentally transformed our understanding of subduction zones, illuminating the fierce struggle of tectonic plates colliding deep beneath the Earth’s surface and revealing the raw, primal forces that govern our planet.

Sumatra’s Great Quake (2004)

December 26, 2004. A 9.0 undersea quake off Sumatra unleashed a tsunami that drowned over 156,000 people across a dozen countries. Gravity meters in Australia picked up the Earth’s shudder two weeks later, says Herb McQueen at Australian National University. According to Herb McQueen, “We can still see a steady signal of the earth vibrating as a result of that earthquake two weeks later. From what it looks like, it appears it will probably continue to oscillate for several more weeks.”

More potent than most big quakes by a factor of ten, it keeps the planet vibrating like a struck gong. Right after the jolt, the ground heaves 20 to 30 centimeters—matching the moon’s tug—before easing to millimeters. That stubborn hum lingers, fading slowly, proving one snap can jolt our world for weeks. NASA’s Richard Gross figures it even shaved microseconds off our day and tilted Earth’s axis a smidge, a cosmic nudge from a single blow.  

Greenland’s Mystery Signal (2023)

In September 2023, a strange hum was detected circling the Earth for nine days, traveling from Greenland to Antarctica in under an hour. Stephen Hicks from University College London traced the source to Dickson Fjord, where a landslide dumped 25 million cubic meters of rock—enough to fill ten Giza pyramids—into the water. The impact generated 200-meter-tall tsunami waves, which were trapped by the fjord’s narrow walls. These waves surged every 90 seconds, turning the valley into a booming drum that wouldn’t stop.

Initially, seismologists were puzzled. However, drones and satellites identified the cause and concluded that thinning glaciers, weakened by climate change, allowed the slope to collapse. Climate change loaded the gun, and nature pulled the trigger. Global sensors picked up every beat, demonstrating that we can detect trouble brewing in some of the Earth’s most isolated areas. Hicks also discovered wave scars etched into the cliffs of the fjord—a silent testament to the event that occurred.

Predicting Disasters from Earth’s Echoes

Earth’s vibrations are like an ongoing conversation that continues even after someone leaves the room; they don’t just fade into silence but shape our future. These planetary movements tell a story that goes beyond mere ground shifts; they reveal the deep interconnectedness of our world, from the ocean depths to the vastness of space.

The future of science looks promising. Advanced satellites equipped with upgraded sensors will capture more subtle vibrations that we miss. Machine learning algorithms are improving at distinguishing the Earth’s continuous background hum from its more dramatic, bell-like sounds. This progress could provide us with invaluable extra minutes of warning before tsunamis reach distant shores.

Perhaps the most fascinating aspect is how Earth’s vibrations connect us all. When the planet trembles after a significant event, the resulting waves travel through every nation, beneath every ocean, and everyone’s feet—a powerful reminder that we share a single, vibrating sphere. The same signals that could warn coastal communities of impending tsunamis might someday help predict volcanic eruptions or detect covert weapons tests.

Featured Image Source: Shutterstock

Source:

1. Inchin, P., Snively, J., Zettergren, M. D., Kaneko, Y., & Komjathy, A. (2021). Modeling of Upper Atmospheric Responses to Acoustic-Gravity Waves Generated by Earthquakes and Tsunamis. , (). https://doi.org/10.5194/egusphere-egu21-5769
2. Kristian Svennevig et al., A rockslide-generated tsunami in a Greenland fjord rang Earth for 9 days.Science385,1196-1205(2024).DOI:10.1126/science.adm9247