Abstract
The present study aimed to characterize the properties of a laser-generated seismic source for laboratory-scale geophysical experiments. This consisted of generating seismic waves in aluminum blocks and a carbonate core via pulsed-laser impacts and measuring the wave-field displacement via laser vibrometry. The experimental data were quantitatively compared to both theoretical predictions and 2D/3D numerical simulations using a finite element method. Two well-known and distinct physical mechanisms of seismic wave generation via pulsed-laser were identified and characterized accordingly: a thermoelastic regime for which the incident laser power was relatively weak, and an ablation regime at higher incident powers. The radiation patterns of the pulsed-laser seismic source in both regimes were experimentally measured and compared with that of a typical ultrasonic transducer. This study showed that this point-like, contact-free, reproducible, simple-to-use laser-generated seismic source was an attractive alternative to piezoelectric sources for laboratory seismic experiments, especially those concerning small scale, sub-meter measurements.
Highlights
Reproduction of seismic wave propagation at the laboratory scale (De Cacqueray et al 2011; Barriere et al 2012; Bordes et al 2015; Valensi et al 2015; Holzhauer et al 2017; Pageot et al 2017; Devi et al 2018) is a promising approach that could lead to significant progress in imaging complex media and monitoring at the near-surface and crustal scales
We have explored the possibility of using a pulsedlaser beam emitted by a Q-switched laser as a seismic source for geophysical laboratory experiments
Our experimental setup was composed of a pulsed laser, a convergent lens focusing the original laser beam (9 mm in diameter), aluminum blocks, and a laser Doppler vibrometer (LDV) to measure the seismic displacement at the surface induced by the pulsedlaser source
Summary
Reproduction of seismic wave propagation at the laboratory scale (De Cacqueray et al 2011; Barriere et al 2012; Bordes et al 2015; Valensi et al 2015; Holzhauer et al 2017; Pageot et al 2017; Devi et al 2018) is a promising approach that could lead to significant progress in imaging complex media and monitoring at the near-surface and crustal scales. The results obtained at the laboratory scale may be applied at the field scale using upscaling methods (Backus 1962; Capdeville et al 2010; Dvorkin and Wollner 2017). We investigated the applicability of a pulsed-laser seismic source (Martin et al 1994; Rasolofosaon et al 1994; Lebedev et al 2011; Mikesell et al 2012) in experiments as an
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