Microseismicity appears to outline highly coupled regions on the Central Chile megathrust

Abstract

We compiled a novel microseismicity catalog for the Central Chile megathrust (29-35◦S), comprising 8750 earthquakes between 04/2014 and 12/2018. These events describe a pattern of three trenchward open half-ellipses, consisting of a continuous, coast-parallel seismicity band at 30-45 km depth, and narrow elongated seismicity clusters that protrude to the shallow megathrust and separate largely aseismic regions along strike. To test whether these shapes could outline highly coupled regions (“asperities”) on the megathrust, we invert GPS displacement data for interplate locking. The best-fit locking model does not show good correspondence to seismicity, possibly due to lacking resolution. When we prescribe high locking inside the half-ellipses, however, we obtain models with similar data fits that are preferred according to the Bayesian Information Criterion (BIC). We thus propose that seismicity on the Central Chile megathrust may outline three adjacent highly coupled regions, two of them located between the rupture areas of the 2010 Maule and the 2015 Illapel earthquakes, a segment of the Chilean margin that may be in a late interseismic stage of the seismic cycle.

Impact of the Juan Fernandez Ridge on the Pampean Flat Subduction Inferred From Full Waveform Inversion

“…Magenta dots in panels (b)–(d) denote the seismicity relocated by Sippl et al. (2021) and in other profiles are retrieved from ISC‐EHB catalog. All the labeled tomographic anomalies can be found in the main text.…”

“…Horizontal depth slices for isotropic . The large and small magenta circles are seismicity from ISC-EHB catalog and the relocated catalog from Sippl et al (2021), respectively, within 10 km of the nominal depth of the slice. The off-shore pink-shaded area indicates the position of the weakened oceanic lithosphere detected by Kopp et al (2004) along the Juan Fernandez seamount ridge.…”

Microzoning Tsunami Hazard by Combining Flow Depths and Arrival Times

“…A high tsunamigenic potential due to megathrust earthquakes exists offshore of the cities of Valparaíso and Viña del Mar, in Central Chile, where regions of high frictional strength have been identified (Sippl et al, 2020). The expected rupture zone roughly coincides with the most populated coastal zone of metropolitan Chile (Figure 2), including the cities of Viña del Mar and Valparaíso, which are home to about 40,000 people that live within the inundation zone.…”