Detection of subsurface structures with a vehicle-based atom gravity gradiometer

TL;DR

This paper introduces a highly sensitive, compact atom gravity gradiometer integrated into a vehicle, enabling effective detection of subsurface structures and water depth measurement in field surveys, demonstrating superior spatial resolution over traditional methods.

Contribution

The development of a portable, high-sensitivity atom gravity gradiometer with an ultra-compact sensor head for practical mobile geophysical surveys.

Findings

Achieved a sensitivity of 77 E/√Hz and stability better than 0.5 E in the lab.

Successfully detected subsurface structures and measured reservoir water depth with high accuracy.

Demonstrated superior spatial resolution compared to traditional gravimeters.

Abstract

High-precision mobile gravity gradiometers are very useful in geodesy and geophysics. Atom gravity gradiometers (AGGs) could be among the most accurate mobile gravity gradiometers but are currently constrained by the trade-off between portability and sensitivity. Here, we present a high-sensitivity mobile AGG featuring an ultra-compact sensor head with a volume of only 94 L. In the laboratory, it achieves a sensitivity of 77 E/$\sqrt{Hz}$ (1 E=1$\times10^{-9}$/s$^2$) and a long-term stability of better than 0.5 E. We integrated the instrument in a minivan, enabling efficient mobile field surveys with excellent maneuverability in confined spaces. Using this vehicular system, we surveyed the gravitational field over a set of subsurface structures within a small wooded area, successfully resolving their structural signatures with a signal-to-noise ratio of 57 and quantifying the water depth in a reservoir with an accuracy of $\pm$0.23 m. Compared with previous observations using a CG-5 gravimeter, the superior spatial resolution inherent in gradiometry is clearly demonstrated. This work paves the way for bring AGGs to practical field applications.