Generator of seismic rotational motions

Jiri Malek and Johana Brokesova

Two prototypes of mechanical generator of seismic rotational motions are presented. Generator is anchored with its fixed part in the ground, and the mobile (rotary) part of the generator, after being activated, is stopped instantaneously by the braking mechanism; this instantaneous stopping transmits energy into the rock massif. An advantage of the generator is its relatively small dimensions and weight, which makes it easy to move in the field. The generator is designed to be used for sequentially repeated experiments, so that essentially the same pulse of rotational seismic waves is generated. The signals from repeated measurements may also be combined in the control unit in order to achieve high sensitivity by suppressing noise via stacking. Non-linear combination of signals can be applied for this purpose. The generator is intended for use in a measuring set together with mechanical rotational sensor system (Rotaphone).