Seismic Linear-Synchronous Motor Vibrator

General Information

Instruments:
Seismic Linear-Synchronous Motor vibrator.

Description:
The Seismic Linear-Synchronous-Motor vibrator is a (transportable) monitoring vibrator for investigations down to depths of one kilometre on land. It allows to generate low-frequency signals such that methods like Full-Waveform-Inversion can be used on the results.

Location:
Laboratory of Geoscience and Engineering, Faculty of Civil Engineering and  Geosciences, Stevinweg 1, Delft (Building #23).

Key Words:
Seismic vibrator, seismic monitoring, LSM vibrator.

Main Application:
Seismic investigations on land, down to one kilometer.

Instrument Specification:
The seismic vibrator, based on Linear Synchronous Motors, allows to generate signals between 2 and 200 Hz with full force. Especially the low-frequency specification, that includes low harmonic distortion at those low frequencies, makes this vibrator unique since its weight is “only” some 1250 kg.  Since the signal is generated with motors based on electro-magnets, pseudo-random sweeps  can easily be generated. 6 linear synchronous motors are inside the vibrator, being able to create a force up to 6.7 kN.  The maximum stroke of the vibrator is ±42 mm, the most limiting factor on the low-frequency side.  The vibrator can be used nearly continuously, making it very suitable for seismic monitoring of the shallow subsurface, next to being very suitable for combined use with Full-Waveform Inversion for which the low frequencies are necessary.