Paleoseismology of the Marquesado-La Rinconada thrust system, Eastern Precordillera of Argentina

Excavated trenches at two sites across the Marquesado–La Rinconada fault system along eastern Precordilleran front south of San Juan, Argentina, reveal earthquake history this rapidly urbanizing region. Interpretation earthquakes is based on both generation colluvial wedges and upward terminations, as well folding events in fine-grained alluvium ponded behind upslope-facing scarps. The ages past five interpreted Loma Negra site are E1 2.8 ± ka, E2 7.1 1.5 E3 9.6 1.3 E4 14.4 2.1 E5 17.2 3.1 ka. At Jejenes sites, we documented event 2.7 0.1 3.9 0.6 5.9 11.4 4 These results indicate that recurrence interval zone averages several thousand years. inferred displacements about 1.1 m for E1, E3, E2, whereas averaged 1 m, but most recent displays less slip. Notably, older seem to have been larger emergent, youngest appears smaller blind sediment; may partially explain poor expression classic associated with some events. Despite fact active surface faulting has an uncertain relationship primary seismic sources depth crust, future M w ?7.5 consistent length scale deformation, ?1–2 slip per these ruptures, size historical earthquakes.