Tracing the relationship between the upper plate earthquake cycle and megathrust slip, the Atacama fault system in Northern Chile

Abstract

Abstract Inland-normal faulting is recognised as an important process following large subduction earthquakes. The lack of data limits the understanding of how normal fault reactivation relates to the subduction earthquake cycle. We characterised the palaeoseismology of the Atacama fault system (AFS) in the Chilean subduction zone. Our results showed that upper plate normal faulting earthquakes with Mw 7.0 and recurrence intervals of 35 ± 9 ky generated surface ruptures preserved as fault scarps. The average fault slip rate of 0.07 ± 0.01 m/kyr is three orders of magnitude slower than the convergence velocity, and the recurrence intervals of surface-rupturing earthquakes on the studied faults are much larger than the recurrence of great to giant (Mw > 8.5) subduction earthquakes in the Chilean margin. This demonstrates that the reactivation of an individual fault in the AFS is not always synchronised with this type of subduction earthquake.

Keywords

• Palaeoseismology
• Upper plate fault
• Chilean subduction
• Atacama fault system
• Luminescence dating
• Seismic hazard