Advanced data processing of airborne electromagnetic data for imaging hidden conduit networks in the coastal karst plain of Tulum (Mexico)

Abstract

This study is part of a series of international research cooperations which commenced in 2007 and are still ongoing. The study area is located on the east coast of the Yucatan Peninsula, Mexico, and comprises the northernmost part of the Sian Ka’an biosphere reserve, a coastal wetland of international importance, as well as the city of Tulum in the state of Quintana Roo, and part of the second largest barrier reef in the world some 300 metres to one kilometre off shore. Two airborne surveys, conducted in 2007 and 2008 by the Geological Survey of Austria, covered an area of some 200 square kilometres, including the well-known Ox Bel Ha cave system, already mapped by exploration divers. In order to get additional ground truth data and input for the hydrological model, extended ground geophysical campaigns have been conducted annually. The first processing of the airborne electromagnetic (AEM) data revealed not only a clear signature from known caves but also the image of a vast, unexplored, hidden conduit network. However, lateral and depth resolution was limited due to measurement drift and noise as well the specific behaviour of the applied inversion technique. Newly developed algorithms for processing AEM data and inversion results have improved the signal-to-noise ratio significantly and enabled the imaging of well-defined structures in the underground. Therefore, the AEM method is now capable of quickly delivering crucial structural information of karst-water regimes in difficult-to-access areas with unique depth information compared to previous studies.