University of Texas at Austin earthquake engineering mobile shaker equipment designed specifically for low-frequency, large-motion operation. The single-axis actuator is shop-transformable to horizontal or vertical modes. The maximum force output in both modes is about 89 kN down to a frequency of 1.3 Hz. However, a new testing configuration allows peak dynamic forces up to 89 kN down to 0.7 Hz. Below 0.7 Hz, the force level decreases but is still substantial to about 0.6 Hz. This modification has significant implications for deep (1 km or more), active-source subsurface imaging. Equipment is mounted on an off-road vehicle and has penetrometer/instrumentation pushing capability mounted on the rear of the vehicle.