While clearly occurring within the well-defined Northern Chile seismic gap, the 2014 Mw. 8.1 Iquique Earthquake only ruptured part of this gap, leaving large and possibly highly coupled areas untouched. These non-ruptured areas now may pose an elevated seismic hazard due to the transfer of stresses resulting from the 2014 rupture. Here we use recently collected multibeam bathymetric data, covering ~90% of the North Chilean marine forearc, in combination with unpublished seismic reflection images to derive a tectonic map of the marine forearc in the unbroken segment of the seismic gap. In the entire study area we find evidence for widespread normal faulting. Seaward dipping normal faults locally extend close to the deformation front at the deep-sea trench under 8 km of water. Similar normal faults on the lower slope are neither observed further north (2014 Iquique earthquake area) nor further south (2007 Tocopilla earthquake area). On the upper continental slope, some of the normal faults dip towards the continent, defining N-S trending ridges that can be traced over tens of kilometers. The spatial variations in normal faulting do not correlate with obvious changes in the structural and tectonic setting of the subduction zone (e.g. plate convergence rate and direction, trench sediment thickness, subducting plate roughness). Thus, the permanent deformation recorded in the spatial distribution of faults may hold crucial information about the long-term seismic behavior of the Northern Chile seismic gap over multiple earthquake cycles. Although the structural interpretations cannot directly be translated into seismic hazard, the tectonic map serves to better understand deformation in the marine forearc in relation to the seismic cycle, historic seismicity, and the spatial distribution of plate-coupling

American Geophysical Union Fall Meeting, 12-16 December 2016, San Francisco

Peer Reviewed