Experts are trying to determine what caused two Labor Day earthquakes.
On Monday, the second earthquake, which measured 4.3 on the Richter Scale, happened two miles west-northwest of Timpson in Shelby County, near where the first earthquake, a 4.1, occurred just two hours earlier.
That makes 14 quakes in Shelby County recorded since May of last year.
However, Dr. Wesley Brown, a geology professor at Stephen F. Austin University, said he has recorded many more than 14.
"I have a list here and the last one on my list is 66," said Dr. Brown said.
Brown said thanks to some seismographs in the field, they can detect small tremors that are not always recorded by the U.S.G.S.
"These that we were having yesterday could be considered your aftershocks. It's not uncommon for you to have aftershocks of earthquakes long after you've had a main shock because rocks continue to adjust themselves to release stress within the earth," Dr. Brown said.
However, Monday's rattling has not been confirmed as aftershock. Another geology professor said the depth of Monday's earthquake helps narrow down the sources.
"We are on a natural fault line and it is also true that there are a lot of oil and gas projects going on around here. There's some fracking that's being done, there's some disposal of waste water, and we know that those things can cause earthquakes, but the problem when you try and pin those on this earthquake is that the U.S.G.S. is saying this occurred at a depth of three miles, and that's a lot deeper than where you typically see these kind of fracking operations and stuff like that going on," said Rebecca Harper, Professor of Geology at Tyler Junior College.
Fracking, aftershocks, Mother Nature...there are several theories, yet none are confirmed.
"We might not be ever able to say for sure what is causing them, but if what is causing them is still there then they might continue," Harper said.