Shallow imaging using ground-penetrating radar (GPR) data in a carbonate environment: Belize, Central America

Monica Moldoveanu-Constantinescu, Robert R. Stewart, Julie Ann Aitken

During the summer of 2002, seismic and ground-penetrating radar (GPR) surveys were successfully conducted in northwestern Belize, Central America. The 2002 field season was initiated to explore more of the shallow section and two archaeological sites (Ma'ax Na site and Chan Chich). This paper describes the GPR surveys carried over the Ma'ax Na structures and analyzes the data acquired in this area. Thirty GPR lines were acquired during the 2002 field season, using Sensors & Software Inc's Noggin system with a 250-MHz antenna. Most areas had loose soils and forest debris overlying rubble or competent carbonates.

Preliminary analysis of the data gives velocities from 0.072 m/ns (for a depth of 1 m) to 0.106 m/ns (for a depth of 0.7 m).

Different types of gain (true amplitude recovery, automatic gain control) and filters were applied on the data to enhance the deeper reflectors. Using the velocity values determined during the acquisition, we estimate that the maximum depth from which we have reflections is between 1 and 3 metres. Good comparison between two reversed lines indicates that the method provides repeatable results. A project conducted over a few caves provided good imaging of these structures and indicated the effective applicability of the method in a carbonate environment. The method was successful in interpreting the locations of the caves.