A closer look at the geometry of the Pampean flat slab’s southern termination

We use a newly retrieved seismicity catalog that contains > 115,000 double-difference relocated events in the vicinity of the southern termination of the Pampean flat slab in Central Chile and NW Argentina to infer the slab configuration at the transition between flat and normally dipping slab. We find that the Pampean flat slab shows a slight downward dip towards the south in its eastern part, whereas the normally dipping slab further south does not extend deeper than the inclined part of the flat slab, updip of the flat segment. From the geometry outlined by seismicity alone, it is not possible to distinguish whether a sharp bend or a tear in the slab is present at this location. When putting our observations into context of existing constraints from a range of disciplines, it appears that a limited-scale along-dip tear in the slab at this location is the scenario that is most easily compatible with all existing evidence.