A pulsed diode laser for tectonic aerosol lidar sensing

Abstract

Previously, we have observed a correlation between Earth’s seasonal crust deformations, measured by a laser strainmeter, and backscattering signal acquired during tectonic aerosol laser sensing using a compact lidar (laser radar). It was established that large sensing track partition step (5 m) combined with relatively short sensing track length (strainmeter tunnel length 17.5 m) leads to partial mixing of aerosol backscattering and track round-trip transmission signals. To reduce the influence of this factor a new lidar has been developed based on a diode laser pumped by pulses of current which generates remarkably short light pulses (~1.5 ns). This allowed to shorten the track partition step 50-fold (to 10 cm). Calculations and experimental measurements have shown that such partition step shortening allows for multiple increase in signal-to-noise ratio in the lidar data. As the tectonic aerosol variations are a new indicator of Earth’s crust deformations, such an increase in the lidar signal sensitivity to aerosol variations undoubtedly opens new possibilities for the search of earthquake precursors.