More than 50 aftershocks have been recorded after a 4.8-magnitude earthquake in New Jersey shook the tri-state area last Friday, the U.S. Geological Survey said.

Now, the USGS is deploying ‘aftershock kits’ in the area to better document data from aftershocks. Eight kits will be deployed this week to track where the aftershocks originate, how long they last, and how strong they are, the USGS announced Thursday.

The USGS said more than 50 aftershocks have occurred so far since the April 5 quake and have ranged from magnitude 1.3 to 3.8. The USGS is forecasting a 12% chance of a magnitude 3 or larger aftershock in the next week and just a 1% chance of a quake magnitude 4 or larger.