14 / 44 shaking the surface of the ground with a compact item of portable equipment called the vibrator source elvis iii. ?e vibrator weighs just 35 kg and pro- duces acoustic waves. when elvis iii stamps, the movement is transmitted as compression waves, or p-waves. when elvis iii shakes the surface from side to side, the movement is transmitted as waves that ?twist? the surroundings, and are known as shear or s-waves. ?e movements of the waves are reg- istered by 96 geophones, which are small cylinders that are placed in a line at one-metre intervals for almost 100 metres. ?is means that the equipment is able to collect geological data down to a depth of 100 metres. when janina kammann then processes the data on her computer, she is able to show im- ages of the