loading page

Improved Imaging of the Large-Scale Structure of a Groundwater System with Airborne Electromagnetic Data
  • Seogi Kang,
  • Rosemary Knight,
  • Meredith Goebel
Seogi Kang
Stanford University

Corresponding Author:[email protected]

Author Profile
Rosemary Knight
Stanford University
Author Profile
Meredith Goebel
Stanford University
Author Profile

Abstract

Working with airborne electromagnetic (AEM) data acquired in the Kaweah Subbasin in the Central Valley of California, U.S.A., we developed a new approach for imaging the top of the bedrock and the confining Corcoran Clay layer. Our approach included multiple L2-norm and Lp-norm inversions as well as an interpolation process. The major improvement in imaging the two targets was made in the Lp-norm inversion step by incorporating prior knowledge. For the Corcoran Clay, pairs of resistivity and driller’s logs at two wells guided the selection of the best resistivity model and were used to increase the accuracy of the estimated Clay thickness. The bedrock surface was poorly constrained by well data in the existing groundwater model, appearing as a flat surface. We had good AEM data coverage in the area so had higher confidence in the obtained map of the bedrock surface at depths ranging from 15 m to 160 m. There was relatively good agreement between the location of the Corcoran Clay in the AEM data (depth ranging from 50 to 130 m and thickness ranging from 3 to 25 m) and the existing groundwater model, with both depth and thickness showing ~15% relative difference. The AEM data provided information about the continuity of the Corcoran Clay that is challenging to capture in the well data. The locations of the bedrock and Corcoran Clay were used in a structurally-constrained inversion to improve the imaging of the smaller-scale resistivity structure.
Apr 2022Published in Water Resources Research volume 58 issue 4. 10.1029/2021WR031439