Seismic tomography of a Maya pyramid ruin, Chan Chich, Belize

Chuandong Xu and Robert R. Stewart


In March 2001, a series of seismic surveys were conducted over a Maya ruin complex at Chan Chich, Belize, Central America. As part of these studies, a seismic tomography survey, using three-component (3-C) geophones and a hammer source, was undertaken around Structure A-15 (an 18 m high pyramid ruin). We used 27 source locations with 20 3-C geophones, all with a 2.5 m spacing on a contour around the pyramid. In this paper, we analyze the three-component datasets and their spectra (0-250 Hz), pick first-break arrivals from 540 vertical component seismic traces, and perform a traveltime inversion to estimate the velocities inside the pyramid. We find a P-wave velocity structure of about 400 m/s for the detrital layer on the pyramid with interior values of 500 m/s to 700 m/s. These velocity results are in reasonable agreement with those found in a similar, preliminary experiment in 2000 at Chan Chich (Xu and Stewart, 2000). There is evidence of a low-velocity anomaly among the higher velocity areas.

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