Bathymetry, Seabed Sediments and Aquifers Imaging with Constrained Inversion of Airborne EM Data

A shallow (depth < 20 m) layer of water, fresh, brackish or saline, covers tens of thousands of km2 of sediments and bedrock along European coastlines, rivers, lakes, and lagoons. These geological units are extremely important, both environmentally and economically. Airborne electromagnetic (AEM) data has been lately used to obtain the bathymetry of shallow surface water. Some attempts have also been made to retrieve information about the sub-bottom. The limited research carried out so far calls for improvements and further developments, both hardware and in data processing and modelling. This manuscript aims at giving a contribution at data inversion level, by applying to different AEM datasets flown over water the constrained inversion methodology. In this technique, adjacent model parameters are regularized through lateral constraints that allow information to flow from soundings that contain more to those that contain less. We present results from constrained inversion (smooth and few layers) of a portion of SkyTEM survey flown over the North Sea. Bird height was included as an inversion parameter. Both the seabed and the freshwater coming from land and protruding into the sediment under the seabed are imaged. Other case studies from lakes and rivers will be presented at the conference