Abrupt increase in the coastal uplift and earthquake rate since ∼40 ka at the northern Chile seismic gap in the Central Andes

Abstract

Over long-term geological scales, the position and vertical movements of the coast are considered to be among the most important effects resulting from first-order plate tectonics interactions in the subduction zones. However, the relationship between short-term vertical deformation driven by earthquakes and long-term coastal uplift in the Andean subduction contact of northern Chile has not been thoroughly elucidated to date. Based on precise radiocarbon dating and geomorphological analysis of littoral deposits in the Mejillones Peninsula at the southern edge of the major northern Chile seismic gap, we report a drastic increase in coastal uplift since marine isotope stage 3 (MIS 3) with uplift rates one order of magnitude more rapid than previously in the Late Pleistocene. Geomorphological evidence supplied by Holocene littoral deposits and marine terraces shows that this tectonic regime could be operating at present. Together with new geodetic data following the 2007 Mw7.7 Tocopilla event, these observations indicate that coastal uplift results from cumulative coseismic vertical displacement with low subsequent interseismic subsidence recovery driven by both deep-moderate and large megathrust earthquakes. We suggest that the accelerated coastal uprising and earthquake rate over the past ∼44 ka demonstrated in this work results from changes involving the entire subduction contact between the Nazca and South American plates in northern Chile.