Depth-Dependent Recurrence and Slip-Rate Behavior of Repeating Earthquakes in Northern Chile

Repeating earthquakes provide constraints on fault slip and loading processes along subduction zones. We analyze a comprehensive repeating earthquake catalog from northern Chile spanning more than two decades (Folesky et al., 2025), consisting of 3153 repeating earthquake sequences with magnitudes ranging from −0.3 to 4.7. These sequences cluster at two depth intervals: a shallow group (<70 km) and an intermediate-depth group (70–210 km), spanning from the plate interface to within the subducting slab.

We compare the recurrence behavior and slip-rate response of shallow and intermediate-depth repeating earthquakes. Shallow repeaters show strong sensitivity to large megathrust earthquakes. Following the 2014 Mw 8.1 Iquique earthquake, inferred slip rates accelerated to peak values of up to 51.96 cm/yr, then decayed over approximately five years to a quasi-steady level of 3.3449 cm/yr, and eventually returned toward a background rate of 0.549 cm/yr. In contrast, intermediate-depth repeating earthquakes exhibit little systematic response to large megathrust events.

Despite these contrasting responses, both shallow and intermediate-depth repeaters record comparable background slip rates of ~0.5–1.0 cm/yr. Along-strike and space–time analyses further indicate that north–south variability at intermediate depth is expressed primarily in recurrence patterns rather than in slip-rate amplitude. These results demonstrate pronounced depth-dependent differences in repeating earthquake behavior and provide new observational constraints on fault slip processes from the shallow megathrust to intermediate depths.