A series of four earthquakes in a week around Lake Lanier have had residents wondering two questions -- why are they happening, and when will they stop?

On Friday, researchers from several Georgia universities began placing special earthquake sensors below ground. The seismic nodes will sit about one foot deep and will be placed in several locations surrounding the epicenters. The first seismic sensor was installed at Sugar Hill Elementary School in Gwinnett County. R. Scott Harris, University of Georgia adjunct researcher and STEM educator with Gwinnett County Public Schools, and School of Earth and Atmospheric Sciences Professor Zhigang Peng, dug through the Georgia Clay to reach the right depth and placed the sensor and battery system below ground, to be later retrieved later this year.

"There are probably many smaller ones that are happening right now as we speak, but it's always hard to tell when it's going to stop. That's the Million-Dollar question. That's what we're trying to figure out," Dr. Peng explained.