Impact of Atmospheric Pressure Variations on Noise-based Velocity Changes Measurements

Abstract:

Environmental perturbations, such as rainfall, atmospheric pressure loading, and temperature changes can affect crustal seismic velocities. Their respective impacts on seismic velocities in the shallow crust are difficult to untangle as they are often acting together at similar spatial and temporal scales. We take advantage of high-quality seismic data from 40 three-component sensors distributed in 5 boreholes deployed in the desert of the Sultanate of Oman to measure velocity variations in the first top hundred meters depth over four months. During these four months, significant atmospheric perturbations (1 kPa) occurred at different time scales ranging from diurnal to monthly but no precipitation is reported. To explain the observed velocity variations we derive a model that accounts for 1) the loading and 2) the fluid pore pressure diffusion within a trapped aquifer located around 50 m below the surface, both induced by air pressure variations. By providing a new model for explaining the effects of atmospheric pressure variations on crustal seismic velocities we contribute to better understanding the impact of the environment on the shallow crust.