Seismic and radar tomography of a Maya pyramid ruin

Matthew David Allen, Robert R. Stewart

A number of seismic surveys, in addition to a ground penetrating radar (GPR) test, have been conducted on a Maya pyramid ruin at the Maax Na archaeological site in Belize, Central America. The pyramid stands some 15 m high with an approximate 28m by 28 m base. The purpose of these surveys was to determine whether seismic and GPR tomography techniques could be used to create images of the pyramid's carbonate rubble interior. We find that hammer seismic and GPR waves can be transmitted through the pyramid. Transmitted wave traveltimes were picked for all the surveys and used in a traveltime inversion to create velocity maps of the interior.

Two different approaches were used to find the velocity structure. A straight ray approach successfully solved for velocity models with average traveltime residuals (measured minus calculated) measuring approximately 1.6 ms for the seismic surveys and 2.9 ns for the GPR surveys. The curved ray technique solved for a velocity model with improved average residuals for the lower seismic survey of approximately 1.5 ms. However, the average residuals increased for both the upper seismic and GPR survey to values of approximately 3.9 and 4.3 respectively. This method produced no unphysical values but tight velocity constraints had to be implemented.