Cambios Periódicos De Gravedad Vinculados Con Tectónica Activa En La Precordillera Oriental, San Juan, Argentina
Francisco Ruiz, Mario Gimenez, Antonio Introcaso, Patricia Martinez, Laura Cornaglia, Flavia Leiva and Jorge Sisterna
Event name: 11th International Congress of the Brazilian Geophysical Society
Session: Gravity & Magnetics
Publication date: 24 August 2009
Info: Extended abstract, PDF ( 1.3Mb )
The gravity signal contains information regarding changes in density at all depths and can be used as a proxy for the strain accumulation in fault networks. A network of areal geodetic control (Red G1) was set up with the purpose of establishing space-time relations in the evolution of the gravity field produced by seismo-tectonic activity. The network is composite for 50 points well materialized in the field, and extends over an about 2700 km2 area centered in the San Juan city of Argentina. These bench marks were linked with precise gravity measurements carried out during the years 2000, 2004, 2007 and 2008. The gravity changes are evaluated taking as fix the gravity value in the Instituto Geofísico Sismológico (UNSJ) station. The relative gravity variation field shows a consistent relation with the seismic activity with magnitudes higher than 3 in the area, which was frequent during these years. The most outstanding results indicate that: A) An alignment of maxima with variations up to +0.100 mGal occurs in the Southwest of the Pie de Palo range, Barboza and Valdivia interior mountains. B) A generalized descent in gravity changes to the east of Sierra Chica de Zonda range (topographic uplift). C) The South of the Sierra Chica de Zonda range shows a marked quiescence in the bench marks situated to the west and high changes (-0.090 mGal) to the East of the range. D) A generalized gravity down (upward zone) in the stations situated north of the San Juan River in the interval 2004-2000. If we assign the gravity variations as caused entirely by topographic changes, the height variations would be in the neighborhood of 20 cm in the last 10 years.