The Andean subduction zone between 22 and 25°S (northern Chile): precise geometry and state of stress

摘要: Abstract One year of seismicity recorded by a local network is used to obtain more precision about the geometry and stress regime Andean subduction between 22 25°S in northern Chile seismic gap. A sharp image Wadati-Benioff Zone (WBZ) obtained down 270 km depth. seismically quasi-quiescent zone observed WBZ below volcanic arc, 150 210 Hypocentres distant intermediate depth earthquakes located with are compared worldwide hypocentres order evaluate accuracy at greater than 100–150 No shallow microearthquakes have been continental crust but some activity likely occur locally deep root Atacama Fault. The field characteristics faulting along subducted slab investigated. Underthrusting localized reverse define coupled plate interface from 20 50 (Locked zone). Downdip, intra-slab normal prevails (Tensile zone), strike-slip observed. transition variable fault azimuth nearly homogeneous NNW- NW-oriented plane found 80 It that axes σ 1 3 Locked oriented convergence direction (75–80°E). tensile zone, has mean 60–65°E. There, hence submitted tensional force (slab pull) oblique relatively convergence. underthrusting intraplate downdip occurs where Moho encounters Zone, suggesting relationship exists coupling presence interface. pre-seismic state this segment confirmed occurrence strong global around presumed rupture area Zone.