Mobile seismic exploration

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 ov...

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Bibliographic Details
Main Authors: Dräbenstedt, A., Cao, X., Polom, U., Pätzold, F., Zeller, T., Hecker, P., Seyfried, V., Rembe, C.
Format: Conference Proceeding
Language:English
Subjects:
Aerodynamics
AIR
AMPLITUDES
APPROXIMATIONS
AUTOMOBILES
BEAMS
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
DATA
DETECTION
DOPPLER EFFECT
EXPLORATION
FREQUENCY RANGE
HOLES
Inertial sensing devices
Infrared lasers
Laser beams
LASER RADIATION
Lasers
Microelectromechanical systems
NOISE
Noise levels
RESOLUTION
SEISMIC DETECTORS
SEISMIC WAVES
SENSITIVITY
Sensors
Tables
TURBULENCE
VELOCITY
Vibration
Vibration measurement
WAVELENGTHS
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Summary: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.
ISSN:0094-243X
1551-7616
DOI:10.1063/1.4952659