How common are earthquakes on the East Coast? Are they different from West Coast quakes? Your questions, answered.

The Globe spoke with Paul Caruso, a geophysicist with the USGS; Lingsen Meng, an associate professor in geophysics at the University of California, Los Angeles; John E. Ebel, a senior research scientist at the Weston Observatory; Karen M. Fischer, a professor and seismologist at Brown University; and Victor Tsai, a geophysicist at Brown, to learn more.

These interviews have been condensed and lightly edited for clarity.

Caruso: Well, they’re relatively uncommon. We did a search of the earthquakes in the area of this one, and this is the only magnitude 4 or larger that we’ve had in this area since 1970. In 2020, on the 9th of September, there was a magnitude 3.1 near Marlboro, New Jersey, and that was the only other quake we’ve had that was larger than magnitude 3 in that area. So quakes here are relatively uncommon. We get small ones. There’s lots of magnitude 2s and 1.5s. But for magnitude 4 or larger, this is the only one we’ve had that we’ve recorded in this area.

Meng: The East Coast is something we call the passive margin, as opposed to active margins on the West Coast. On the East Coast, earthquakes are generally rare, but you have them, just over a long time. The most recent one was in Virginia in 2011. That was a 5.8 — a bigger one. Historically, you have lots more. There was one above magnitude 6 near Boston — I think on Cape Ann in 1755. There was one in Charleston, South Carolina, in 1886 that was a 7.2. These are all much bigger than the one we had today.

Caruso: They’re usually very small, less than magnitude 2 [or] 3. When we did our search, we found in the area of New Jersey that we’ve had over 100 earthquakes since 1970. But most of them were between magnitude 2 and magnitude 1, so relatively small. We’ve had a few that were larger than magnitude 2.

We get some quakes around Massachusetts from time to time. Quakes in New England are not completely unknown. But of course, we cannot predict earthquakes. It’s likely that we’re going to have aftershocks from the one today, but those will be much smaller than the initial earthquake.

Meng: If you look at the historical record over a long time, earthquakes on the East Coast are not necessarily smaller, but they are rare for sure. You can find bigger ones. But just in general, what limits the size of the earthquake is the size of the fault. So generally, when we have bigger faults, and there’s more stress accumulated, we tend to have bigger ones. But not just on the East Coast — like everywhere. Where the biggest earthquakes [happen] are around the Pacific in the subduction zones, like one plate goes under the other one. The reason those earthquakes are bigger is the fault contact area — where the area’s plates kind of touch each other is larger in between the surface and to the depths. Where we have earthquakes, those contact areas are larger.

Caruso: Earthquakes are caused by faults moving underground. When the rocks shift, the rocks move underground and the earth shakes, and we call that an earthquake. In the case of this one, the earthquake occurred at a depth of approximately 5 kilometers, or about 3 miles underground.

We wouldn’t expect any significant damage from a magnitude 4.8. Usually, we don’t start to see damage from quakes until they get up into the magnitude 5-5.5 range.

Meng: The earthquakes within the tectonic plate, we call them intraplate earthquakes. In these places, the plate boundary is very well-defined like on the West Coast, but on the East Coast, there’s no clearly defined big structure or big fault system, so the distribution of these fault lines tends to be more random. There are many blind faults, which means we don’t see them on the surface and we don’t know they can cause an earthquake until it happens. But for the East Coast, I think one possibility is the Appalachian, so that was what we call a suture structure. This goes back to, I don’t know how many hundreds of million years, but they used to be an open ocean, and then the plate tectonics closed it, but it left a scar ... and they have lots of fossilized faults. Under the right conditions, these fossilized faults can be reactivated.

Another possibility is fracking, so artificially induced earthquakes. Those places, when you have the fracking wells ... that can trigger some of the old faults. You probably heard about lots of those kinds of earthquakes in Oklahoma, Texas, and maybe a little bit in Ohio. ... It’s probably a likely cause. Fracking can cause earthquakes, especially in tectonically non-active areas.

Ebel: On average, earthquakes are felt in the New England region maybe three, five, six times per year. Then you add in New Jersey and New York state and into eastern Pennsylvania, and there’s probably another one or two earthquakes felt in those regions. Usually, they’re small and magnitude 1.5 to 2.5. Once a year, maybe a magnitude 3 or a little bit larger. This is like a once-in-20-year type of earthquake.

Tsai: For this specific earthquake, the main reason we felt it up here relatively far away for a relatively small earthquake was because the waves don’t attenuate or die off very quickly in the eastern US. There was a Virginia earthquake back in 2010 and that was felt all over the eastern US at much larger distances than they are usually felt. The primary reason is the Earth’s structure in this part of the world, the waves can pass through it more easily.

Fischer: If this same earthquake happened in California, and they happen there quite frequently, the waves would not be felt as far away. Those rocks are hotter and tend to absorb the energy as it passes through.

Ebel: It wouldn’t surprise me at all if people if the epicentral area (in northern New Jersey) feels aftershocks over the next few days or even a week or more. The most frequent aftershocks will occur within 24 hours of the main earthquake itself, but there could be earthquakes going on for many days and it just gets fewer and fewer after the main shock. The largest is probably going to be about a magnitude 3.5 on average, that’s what we typically observe. People near the epicenter would feel that, but not people up in Boston.

Caruso: California sits on the plate boundary between the Pacific plate and the North American plate. In New Jersey, the plate boundary is actually in the middle of the Atlantic Ocean between the North American plate and the Eurasian plate. So California gets a lot of earthquakes because it sits on a tectonic plate boundary. And the East Coast of the United States does not have very many earthquakes because it’s far away from plate boundaries. The plate boundaries are the most active regions for earthquakes. You may have heard of the quote-unquote Ring of Fire around the Pacific Rim. All those are tectonic plate boundaries and that’s why we have so many earthquakes.

Earthquakes on the East Coast are felt a lot farther away because the rocks there are very continuous as opposed to quakes in California. So in California, if we had the same magnitude quake, it would not be felt nearly as far away because in California, the rocks are young, and they’re full of faults and discontinuities. And on the East Coast, the rocks are very old and so they transmit energy from an earthquake very well. So when we had the Mineral, Virginia, quake in 2011, we had reports of it being felt in Chicago.

Meng: Generally, just speaking about the property of the crust, the crust on the West Coast is younger and hotter. Seismic waves traveling in this crust tend to decay over distance faster; the shaking diminishes quickly over distance. But on the East Coast, we’re dealing with a very old, cold crust, and waves tend to decay much slower on the East Coast. So, whenever you have an earthquake, even of the same size, on the East Coast, it will travel a long distance, so people feel it further away.

Carlos R. Muñoz of Globe staff and Globe correspondent Ava Berger contributed to the reporting of this article.

Shannon Larson can be reached at shannon.larson@globe.com. Follow her @shannonlarson98.