Abstract

COLAVITTO, Bruno et al. Paleoseismological analysis of the Acequión fault by means topographic scarpment profiles (San Juan Precordillera, Argentina). Bol. Soc. Geol. Mex [online]. 2021, vol.73, n.2, 00011.  Epub Jan 31, 2022. ISSN 1405-3322.  https://doi.org/10.18268/bsgm2021v73n2a090121.

The present work focuses on the south tip of the more than 120 km long Matagusanos-Maradona-Acequión tectonic depression, located between the Eastern and Central Precordillera in San Juan province, Argentina. A reverse fault scarp, associated with the Quaternary activity of the east vergent-Acequión fault was analyzed. This fault scarp has an average length of 12 km with a north trend and shows up to ~12 m of throw. After a geomorphological mapping and fieldwork, it was typified as a flexural scarp with a back-thrust pressure ridge. Aided by digital elevation models with 5 m horizontal resolution, we constructed 70 transverse topographic profiles, from which slope breaks and vertical displacement values were extracted and statistically analyzed. Considering the fault scarp classification, the displacement values turned out to be more suitable for the paleoseismological analysis. According to our results, between 4 and 5 minimum Mw 6.5-7.1 earthquakes may have occurred in the Acequión fault since the last ~35 ka. These values have some similarities to those previously obtained by other authors, although future and more detailed paleoseismological surveys should be carried out to test the methodology that was here applied. Additionally, a detailed gravimetric survey was conducted in the southern sector. The geophysical-geological interpretation of residual gravimetric anomalies showed that at least two more north-trending eastern structures parallel to Acequión fault affect the Central Precordillera eastern piedmont.

Keywords : fault scarp; paleoseismology; reverse fault; topographic profile; neotectonics; gravity data.