Long-Term Stability of the 2014 Iquique, Chile Earthquake Rupture Zone: Evidence from Forearc Deformation

Abstract:

The April 1, 2014 M_W=8.1 Iquique (Pisagua), Chile earthquake ruptured a ~250 km long segment of the Nazca-South America subduction zone that last hosted a major earthquake in 1877. Estimated slip up to 8–9 m was concentrated in a region southeast of the hypocenter, and overall, the slip distribution shows spatial correspondence with regions of asperities estimated from geologic data in northern Chile. Tens of thousands of open cracks throughout coastal regions of northern Chile, including several thousand that were freshly opened by the Pisagua earthquake sequence, preserve a record of coseismic stress throughout the past million years. Inversion of these inferred stress orientations for megathrust slip, representing a cumulative or average earthquake on the northern Chilean subduction zone, reveals two concentrations of slip: one coincident with the hypocenter and the other located close to the peak slip estimated from seismic waveform and geodetic inversions from the 2014 event. This suggests that the rupture of various asperities in northern Chile in earthquakes with a 125–150 year recurrence interval may occur repeatedly over neotectonic time scales. Geologic evidence of earthquake-related forearc deformation and the consistency in earthquake rupture patterns that it implies complement the growing body of geophysical data aimed at characterizing the spatiotemporal signatures of seismic cycle processes on the world’s megathrusts.