INVERSION MODELING OF THE COMPLETE BOUGUER ANOMALY FROM THE HONDURAS DEPRESSION

We are analyzing gravity data from the Republic of Honduras, an extremely rugged and mountainous country with numerous deeply incised valleys. One interesting geomorphic feature is a series of discontinuous grabens and topographic lows some investigators call the Honduras depression. The Sula graben forms the north segment of this depression, which continues southward through the Comayagua Valley and ends in the Golf of Fonseca. Interpretation of the simple Bouguer gravity from the Comayagua Valley suggested valley fill is over 3 km thick, placing the floor of this basin over 2 km below sea level. Terrain corrections were calculated for 450 gravity stations within and directly outside the Comayagua Valley and the regional trend estimated and removed from the complete Bouguer anomaly. Because terrain corrections for stations near the valley’s steep margins exceed those for the relatively flat center, maximum valley fill thickness based on the complete Bouguer anomaly exceeds 4 km. Both gravity data and sparse outcrops show that fill thickness is negligible in the northeast corner of the valley. We think that erosion has significantly modified the valley’s morphology since tectonic events first generated this basin. A steep gravity gradient infers a buried scarp (fault?) trending northwest under the old national capitol of Comayagua.