Quad gravity survey of Tegucigalpa, Zamorano Valley, Valle de San Juan de Flores and Morocelí

Abstract

Between July 4 and August 17, 2007, conducted a campaign of gravimetry for the purpose of gathering data relative gravity of the quadrangle areas of Tegucigalpa, Zamorano Valley and Valle de San Juan de Flores and Morocelí. In that campaign they were established 67 stations, with which it formed a local gravimetric network with 24 circuits, interconnected by a base station that is part of the regional network established by NOA-NGS (2001). Throughout the whole area of influence strong negative Bouguer anomalies were found, between -57 and -79 mGals, consistent with previously reported regional values Bowin (1978) and Weyl (1980) associated with isostatic compensation in the central zone of Honduras.

In the valleys of San Juan de Flores (Cantarranas) Morocelí and El Zamorano, appropriate regional severity levels were defined to explore the internal topography of the basement and the depth of alluvium along selected profiles. Using the program GRAVMAG (Burger et al, 2006) that implements the method of Talwani et al, (1959) for calculating residual gravity, we build models of the body of alluvium in two dimensions consistent with the observed residual gravity geology and assuming a contrast -0.4g/cm3 density. More irregular funds were seen deep in the valley of Morocelí, for a longitudinal profile of 37 km where the depths range from 1000, 400 and 1,400 m.

The valleys of San Juan de Flores and Zamorano, however, exhibit a smooth internal topography and maximum depths of 130 and 350 m, respectively. For the metropolitan area of Tegucigalpa developed a contour map of Bouguer anomalies and observed a strong correlation with local geology, with a maximum around -60 mgals associated with the formation Rio Chiquito (Krc) Valley Group Angeles, and low values, down to -80 mGals in areas of volcanic tuffs and sediments of the Padre Miguel Group. This means it is possible to define regional gravity curves associated with the contact zone between these two groups, one very important variable for the local industry geotechnical construction. Our preliminary exploration of the residual gravity field in Tegucigalpa suggests a regional severity level to -67 mGals isostasy corrections in future gravimetric exploration work in this city.

DOI: http://dx.doi.org/10.5377/rct.v0i9.707

Revista Ciencia y Tecnología, No. 9, Diciembre 2011 pp.27-67