Three small earthquakes occurred in Allegheny County earlier this week. The first two occurred early Tuesday morning, the first at 4:41 a.m. and the second about 30 minutes later at 5:16 a.m. Less than 24 hours later, another small earthquake occurred in the same area just after 1 a.m. Wednesday. All three quakes were between magnitude 2.1 and 2.3, and no damage was reported, but several residents in the area reported feeling the tremors. History You may remember a magnitude 5.1 earthquake in Sparta in 2020 that shook North Carolina and surrounding states. This was a very unusual large earthquake, but when we see so many small earthquakes in a row in the same area, it makes you wonder why. Old Fault Lines Although the mountains and foothills are not located along an active plate boundary, the region still experiences small earthquakes associated with old fault lines along the Appalachian Mountains. The Appalachians are some of the oldest mountain ranges on Earth, so it's not surprising that this region is constantly moving and subsiding, but most of the time we can't feel it. Small earthquakes in mountainous areas are nothing to worry about; in fact, they're fairly common and likely too weak to cause any damage.
Three small earthquakes struck Allegheny County earlier this week.
The first two quakes occurred early Tuesday morning, with the first at 4:41 a.m. and the second about 30 minutes later at 5:16 a.m.
Less than 24 hours later, another small earthquake struck the same area just after 1 a.m. on Wednesday.
The three quakes, ranging in magnitude from 2.1 to 2.3, have not caused any reported damage, but several residents in the area have reported feeling the tremors.
history
You may remember the magnitude 5.1 earthquake that hit Sparta in 2020, shaking North Carolina and surrounding states. It was a very unusual large earthquake, so why are there so many smaller earthquakes happening in the same area?
Old fault lines
Although the mountains and foothills do not lie along an active plate boundary, the region still experiences small earthquakes associated with old fault lines along the Appalachian Mountains.
The Appalachians are some of the oldest mountain ranges on Earth, so it's not surprising that the region is constantly shifting and subsiding, though most of the time we can't feel it.
Small earthquakes in mountainous areas are nothing to worry about – in fact, such earthquakes occur relatively frequently and are considered too weak to cause damage.
