Mobile seismic exploration
- Research & Development, Polytec GmbH, Waldbronn (Germany)
- Institute of Flight Guidance, TU Braunschweig, Braunschweig (Germany)
- Clausthaler Umwelttechnik Institut CUTEC, Clausthal-Zellerfeld (Germany)
Laser-Doppler-Vibrometry (LDV) is an established technique to measure vibrations in technical systems with picometer vibration-amplitude resolution. Especially good sensitivity and resolution can be achieved at an infrared wavelength of 1550 nm. High-resolution vibration measurements are possible over more than 100 m distance. This advancement of the LDV technique enables new applications. The detection of seismic waves is an application which has not been investigated so far because seismic waves outside laboratory scales are usually analyzed at low frequencies between approximately 1 Hz and 250 Hz and require velocity resolutions in the range below 1 nm/s/√Hz. Thermal displacements and air turbulence have critical influences to LDV measurements at this low-frequency range leading to noise levels of several 100 nm/√Hz. Commonly seismic waves are measured with highly sensitive inertial sensors (geophones or Micro Electro-Mechanical Sensors (MEMS)). Approaching a laser geophone based on LDV technique is the topic of this paper. We have assembled an actively vibration-isolated optical table in a minivan which provides a hole in its underbody. The laser-beam of an infrared LDV assembled on the optical table impinges the ground below the car through the hole. A reference geophone has detected remaining vibrations on the table. We present the results from the first successful experimental demonstration of contactless detection of seismic waves from a movable vehicle with a LDV as laser geophone.
- OSTI ID:
- 22608637
- Journal Information:
- AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1740; ISSN APCPCS; ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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