Eugene, Oregon, on a Thursday evening in January of 2000: I’d just returned to college from the merriment of festivities around the turn of the century. Classes would begin the following Monday, but for now, college students were partying every night they could. My roommates and I were at a house party when I found myself in the strangest predicament: I’d started reading the Harry Potter series, and I had a strong and unexpected urge to leave the party and go back home to read! (It should come as no surprise that I was about to get a degree in English.)

I went home, but my roommates stayed at the party. I was alone the rest of the night, reading in bed, when all of a sudden, there was a tremendous thud against my bedroom door. It sounded like someone had taken a running start down our hallway and charged at the door. But I was alone. And we lived in a house in the suburbs, so it wasn’t rowdy neighbors, though I did suddenly remember that the woman who had lived there before us had supposedly died in the house.

I froze in fear, staring at the doorknob, waiting for it to turn. Nothing happened. Had it been my imagination? Had I gotten so involved in Harry Potter that I’d imagined something hitting my door? No! The mirror hanging on my door was still vibrating from the impact. I froze again. Still the doorknob didn’t move and I didn’t hear any footsteps. Finally, I got up and locked the bedroom door, not brave enough to confront something outside the door, and also 100% convinced there wasn’t a living thing on the other side of the door.

For years, I’d tell people this story, and they’d try to convince me there was a logical explanation for the event. I didn’t disagree, but I was frustrated by the number of people who didn’t have the slightest bit of curiosity about what that explanation might be. I was even more frustrated by the people who insisted I’d either imagined it or that I’d fallen asleep without realizing it and had just dreamed it. I didn’t know what had happened, but it was not in my head.

Fast forward about a decade, and I was studying earthquakes for my masters degree in Virginia Tech. Between my time in Eugene and my studies at VT, I’d also spent a few years in San Francisco, and I’d even been a historical tour guide in the city during the 100th anniversary of the 1906 earthquake. So I’d experienced a few smaller earthquakes, and I was terrified of being in SF if the Big One struck, but like most people, I thought of earthquakes as something that shook buildings.

One day at VT, I was looking at a chart of what a person might experience for earthquakes of different magnitudes, and there it was: a magnitude 4 earthquake was described as feeling like a truck hit the building! Yes! I’d even experienced that exact sensation in a San Francisco building. A magnitude 4 earthquake struck the city, and I turned to my roommate asking if our building had just been hit by a truck, but she’d lived in the area her whole life and knew it was an earthquake.

But Eugene didn’t get earthquakes, did they? By then, I knew better than to think the answer to that was automatically no. I was studying intraplate earthquakes, which are earthquakes that occur within a tectonic plate, rather than between two plates interacting, and intraplate earthquakes can occur anywhere. I knew how to look up earthquakes, and the Eugene event had left such an impression on me that even years later, I still remembered when it occurred.

I plugged in the location and time frame, and sure enough, a magnitude 4 earthquake had struck that night! It was far enough away to explain why my experience was more like a person charging the door, rather than a truck hitting a building, but there was my logical, non-imagined explanation.

For a while after that discovery, I thought more and more about low magnitude earthquakes and ghosts. Low magnitude earthquakes, especially around magnitude 3 are lower, aren’t typically felt by people, but they have other impacts. The earthquake waves travel at low frequencies, which are known to trigger feelings of dread and paranoia in people. Even though people don’t feel the earthquakes, animals can, and so dogs might bark or get scared and other animals might act weirdly. The right frequency could even do things like knock a picture off a wall or tip a glass over if it’s sitting a little precariously. All of these are classic signs of supposed hauntings. Moreover, many of the most “haunted” regions in the US Southeast are also the most seismically active–but they’re active with low-magnitude earthquakes, so most people aren’t aware the earthquakes are happening or even that they’re in a seismically active region.

I don’t think my earthquake theory accounts for all “ghostly” experiences that people have, but I do think that many supposed paranormal experiences may actually be the result of low-magnitude earthquakes, rather than the supernatural.