Airborne Gravimetry Measurements over Baikal

Abstract

The results of the first high-precision airborne gravimetric route survey, which was conducted in 2023 along a transverse profile of Lake Baikal at a flight altitude of 5300 m, are presented. The use of an airborne gravimetric complex based on the AN-26BRL aircraft–laboratory is described. Directly over the lake, the largest negative measured anomaly of the gravity field was –180.8 mGal and the horizontal gradient of the field measurement was up to 9 and 5 mGal/km for the western and eastern shores of Lake Baikal, respectively. The internal convergence of anomaly values along the route profile for a complex of three gravimeters was 0.74 mGal. The estimations of the resolution and reliability of most topical current global models of the Earth’s gravity field (UGM-SGG-2, EGM2008, XGM2019, and Sandwell and Smith v32) based on satellite data are assessed for the Baikal rift basin. It is shown that the mean square deviations of the field along the entire profile between the values calculated from satellite models with a number of spherical harmonic coefficients of ≥2190 and the airborne gravimetric observations are 9.5‒17.9 mGal, whereas the maximum deviations at individual points of the route are 40–80 mGal. The comparison with data on the marine gravimetric survey on a scale of 1 : 500 000 is carried out using airborne profile data. Due to the highly detailed data along the airborne gravimetry profile, it is established that the factual value of the main negative anomaly on the air profile is higher than that accepted for the analysis and complex interpretation of geophysical data in the area of Lake Baikal.