It’s been about two months since city officials approved Indiana State University’s plans to drill for oil, and now crews have begun seismic testing to map out rock formations under downtown Terre Haute.

The testing is performed by a specially-equipped truck which lowers a pad onto the pavement and sends vibrations of different frequencies into the ground. Computers and other sensors put the results together to tell what’s going on underground.

University officials say the slow-moving truck could cause brief, minor lane blockage over the next week-and-a-half.

The streets affected include: Wabash Avenue, Poplar Street, Chestnut Street and Tippecanoe Street between 3rd and 19th Streets. It will also affect 5th, 7th, 8th and 9th Streets between Tippecanoe and Oak Streets.