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Volume 5 Number 3
  • ISSN: 1569-4445
  • E-ISSN: 1873-0604

Abstract

We apply seismic traveltime tomography in an investigation of the subsurface of a geoarchaeological site at Chatby cemeteries (Alexandria, Egypt). We are interested in obtaining information about the geological structure and the remains of man‐made structures. Energy sources are placed at the surface and recorders are distributed vertically in an underground location. Traveltime data are inverted with a three‐dimensional tomographic algorithm. Inversion results are evaluated and interpreted with the aid of independent geophysical and archaeological information, and various tests are carried out with different initial velocity models and synthetic traveltimes.

The inversion results show good correlation with the estimated geological structure, in particular at deeper levels, as suggested by independent geophysical and archaeological information and later confirmed by excavation. The depth and variations of the bedrock surface are satisfactorily imaged. Indications of possible man‐made structures are presented and discussed. Shallow velocity features are evaluated and interpreted using tests with synthetic traveltimes. The main goal of imaging the deeper structure was successful.

As inversion tests with different initial velocity models indicate, the subsurface structure and the complexity of data information in this particular case are better handled when using a single‐layer model than when using an average two‐layer model. The single‐layer model allows for a more versatile velocity variation and raypath distribution, while the two‐layer model leads to an inversion result that is considerably influenced by the initial velocity distribution. Enhancement of particular aspects of the single‐layer inversion result can be derived with the use of an initial velocity model, that permits a gradual increase of velocity with depth. The gradient model improves the raypath distribution and limits velocity artefacts.

The resulting images can assist in the assessment of the archaeological potential of a site, particularly in excavation design, in a non‐destructive manner. They can be also of great value in other applications, for example in engineering works, when detailed information on the subsurface is sought in areas of restricted access.

© European Association of Geoscientists and Engineers © 2007 European Association of Geoscientists and Engineers
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2018-12-18
2024-04-28

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http://instance.metastore.ingenta.com/content/journals/10.3997/1873-0604.2006033
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Using seismic traveltime tomography in geoarchaeological exploration: an application at the site of Chatby cemeteries in Alexandria, Egypt
Near Surface Geophysics 5, 209 (2007); https://doi.org/10.3997/1873-0604.2006033
/content/journals/10.3997/1873-0604.2006033
/content/journals/10.3997/1873-0604.2006033
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  • Article Type: Research Article

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