The cryptic seismic potential of the Pichilemu blind fault in Chile revealed by off-fault geomorphology

Mapping seismogenic faults and estimating their recurrence times is crucial for assessing seismic hazards. The Pichilemu Fault in Chile, previously unknown, generated a Mw 7.0 earthquake in 2010, highlighting the challenge of mapping blind faults. This study uses off-fault deformed marine terraces to estimate a fault-slip rate of 0.52 ± 0.04 m/ka. Integrating this with satellite geodesy suggests a 2.12 ± 0.2 ka recurrence time for Mw 7.0 normal-faulting earthquakes. The study concludes that extension in the Pichilemu region is linked to stress changes during megathrust earthquakes, accommodated by sporadic slip during upper-plate earthquakes, with implications for assessing seismic potential of cryptic faults.

J. Jara-Muñoz, D. Melnick, S. Li, A. Socquet, J. Cortés-Aranda, D. Brill, M. R. Strecker