The summer night was lit by a slow oscillating wail outside Kasey Aderhold’s home in Homer, Alaska. This siren had been sounded hours earlier as a test of tsunami warning systems, but this time it was a sign that the danger was real.

Some 380 miles to the west, off the coast of the Alaskan Peninsula, a magnitude 8.2 earthquake had just ripped through this part of the planet–the biggest temblor the U.S. has seen in more than 50 years. The event, which struck just after 10 p.m. local time on July 28, jolted nearby shores and sent landslides rushing down the steep coastal mountains.

The quake did not cause any major damage. The quake was far away from dense populations and caused only minor damage. However, such a massive event could be catastrophic elsewhere. A magnitude 8.2 earthquake is almost as powerful as the largest earthquake that could be felt along the San Andreas fault.

“The ‘big one’ that we talk about in Southern California, it’s like that,” says Wendy Bohon, an earthquake geologist at the Incorporated Research Institutions for Seismology (IRIS), an assemblage of research universities that collects, curates, and distributes U.S. seismic data.

This intense shaking had dissipated to gentle rocking by the time it reached Aderhold, an earthquake seismologist also at IRIS. She glanced up to see the hanging stained glass lamp, a remnant of the previous owners. It was slowly swinging from side to side “like an oscillator,” she said.

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The quake serves as a reminder of the instability of our planet’s surface. It also offers an opportunity to look deeper into our planet’s inner workings. The event was so strong, it sent out seismic waves that lit up detectors around the world, even disturbing groundwater levels in Washington County, Maryland.

Scientists can map the Earth’s inner workings using seismic rattles and shakes such as planetary xrays because waves travel differently through rocks of different compositions and temperatures. Scientists can also compare this earthquake to previous events to better understand the potential for future shaking.

Aderhold states, “Every earthquake that we record is going to teach me something new.” It’s exciting to see the data.