Caltech students in Applied Geophysics class (Ge111b), June 1999, operate the seismic "thumper" source while recording a seismic reflection profile. Location: Dallas St., east of Camp Rock Road and south of highway 247 in the Mojave Desert, on the north side of the San Bernardino Mountains. From left to right, the students are: Julie Nazareth, Aron Meltzner, Derrick Hasterok, Mohana Kumar.