Yes, fracking can cause earthquakes. The U.S. Geological Survey (USGS) states that hydraulic fracturing "...causes small earthquakes, but they are almost always too small to be a safety concern. In addition to natural gas, fracking fluids and formation waters are returned to the surface. These wastewaters are frequently disposed of by injection into deep wells. The injection of wastewater into the subsurface can cause earthquakes that are large enough to be felt and may cause damage."
The wastewater injected deep underground exerts pressure on rock formations, causing human-induced fault shifts.