Weather Blog: Early morning earthquake felt all over Arkansas

FOX24

Okay night owls, how many of you think you felt or heard an earthquake early this morning? Well, you were right and it wasn’t just a dream while some of you were sleeping.

At approx 1:42 a.m. CDT, a prelim 3.7 magnitude earthquake was recorded just a little southeast of Gassville or due south of Mountain Home in north-central Arkansas, right in the heart of the Buffalo National River forest area. It was originally recorded as a 3.8, but later downgraded to a 3.7 later in the morning.

The earthquake’s focus or hypocenter (directly beneath the epicenter) was measured at 17.6 km (11 miles) deep beneath the surface.

Lots of people felt it all over the northern half of the Natural State, including right here in NWA. The earthquake was even felt as far away as Kansas City to Memphis and even south of Oklahoma City.

“Did You Feel It” Map Reports from USGS.

We got hundreds of comments on social media saying the shaking was quite noticeable and it lasted a little while. I think it’s interesting how a minor 3.7 fairly deep earthquake (for this area) was felt so far away from the epicenter.

Time for a little geeky science stuff that I think is incredibly interesting. Looking at the two seismographs below, one can determine the speed of the primary shockwave (p-wave) of the earthquake.

Strong motion helicorder showing earthquake hit Yellville seismograph at approx 1:42:30 a.m. CDT (06:42:30 UTC)
Strong motion helicorder showing earthquake hit Hobbs State Park seismograph 15 seconds later at approx 1:42:45 a.m. CDT (06:42:45 UTC)

The earthquake at the epicenter was recorded 1:42:22 a.m. CDT. The shockwave from the earthquake hit the Yellville seismograph 8 seconds later at 1:42:30 a.m. CDT. It started to travel at 2.25 miles per second or 8,100 mph. About 15 seconds later, the p-wave raced to the west accelerating as it hit the Hobbs State Park seismograph 70 miles away from Yellville. If you do the math … the shockwave was traveling at approx 4.6 miles per second or 16,500 mph. MAN, that’s fast and probably the reason your animals were freaking out just before this happened.

Animation of two helicorders showing the 15 second difference.

The composition of the rock in the earth’s crust over the Ozarks and the Springfield Plateau allowed this energy to efficiently travel over long distances, which is why the shaking from this earthquake might have woke you up from a dead sleep. It’s science!

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