Interpretation of the Isostatic State of Cacheuta Subbasin, Using the Undulation of Local Geoide, Mendoza Province

INTROCASO, ANTONIO; GIMENEZ, MARIO E; MARTINEZ, M. PATRICIA; RUIZ, FRANCISCO

Buenos Aires

Congreso; Geodesy for Planet Earth IAG 2009; 2009

International Association of Geodesy

The isostatic study of the Cacheuta Sub-basin was carried out using geoid Nt undulations (Eigen, 2008). Wavelengths exceeding structure’s size were eliminated by filtering methods, thereby leaving the observed residual undulations. We have prepared a perfectly balanced reference model (dipolar crust: - +). Basin depths h were used as input data. Compensating antiroot DR was calculated using the expression DR = 6.675 h.  Using rectangular parallelepipeds to model both sediments and antiriot, residual undulations were calculated from Nr = (-Vs + Var) /g;  with Vs: sediments’ potential; Var: antiroot’s potential and g: gravity. Taking into account the negative sign of the difference Nor – Nr, we have inferred that the basin is isostatically under-compensated and that in the future, it would subside.   Traditional gravimetric methods were used for validation. Both gravimetric method and geoid undulation method agree in corroborating the existence of isostatic under-compensation.  This study clearly shows that N calculations made by means of equivalent sources and plain Stokes confirm consistency of the observed results. A direct passage can be made from N to g and vice versa.  This study also shows that geoid undulations method can replace traditional gravity methods to obtain geological structures and thereby analyzing compensation state without using gravity data.