Earthquake ruptures and topography of the Chilean margin controlled by plate interface deformation

Abstract

Abstract. What controls the location and segmentation of mega-earthquakes in subduction zones is a long-standing problem in Earth sciences. Prediction of earthquake rupture extent mostly relies on interplate coupling models based on Global Navigation Satellite Systems providing patterns of slip deficit between tectonic plates. We here investigate if and how the strongly and weakly coupled patches revealed by these models relate to the distribution of deformation along the plate interface, i.e., basal erosion and/or underplating. From a mechanical analysis of the topography applied along the Chilean subduction zone, we show that extensive plate interface deformation takes place along most of the margin. We show that basal erosion occurs preferentially at 15 km depth while underplating does at 35 ± 10 and 60 ± 5 km depth, in agreement with P-T conditions of recovered underplated material, expected pore pressures and the spatial distribution of marine terraces and uplift rates. South of the Juan Fernández Ridge, large sediment input favors shallow accretion and underplating of subducted sediments, while along northern Chile, extensive basal erosion provides material for the underplating. We then show that, along the accretionary margin, the two last major earthquakes were limited along their down-dip end by underplating while, along the erosive margin, they were surrounded by both basal erosion and underplating. Segments with heterogeneously distributed deformation largely coincide with lateral earthquake terminations. We therefore propose that long-lived plate interface deformation promotes stress build-up and leads to earthquake nucleation. Earthquakes then propagate along fault planes shielded from this long-lived permanent deformation, and are finally stopped by segments of heterogeneously distributed deformation. Slip deficit patterns and earthquake segmentation therefore reflect the along-dip and along-strike distribution of the plate interface deformation. Topography acts as a mirror of distributed plate interface deformation and should be more systematically studied to improve the prediction of earthquake ruptures.

Largest Aftershock Nucleation Driven by Afterslip During the 2014 Iquique Sequence

“…Nadaya Cubas and Hui Huang provided us with the results of Cubas et al. (2022) and Meng et al. (2015), respectively.…”

“…Discussion with Jorge Jara, Zaccaria El Yousfi, Ian McBrearty, Taku Ueda, Michel Bouchon, Satoshi Ide, Jean-Philippe Avouac, and Sylvain Barbot was fruitful. Nadaya Cubas and Hui Huang provided us with the results of Cubas et al (2022) and Meng et al (2015), respectively. Aubin Tsapong helped check the quality of raw GPS observations.…”

Seamount Subduction Dynamics and Long‐Term Evolution of the Franciscan Active Margin

“…Sediment input also strongly depends on the age of the incoming plate (Figure 10e). Thick sediment input enhances underplating (e.g., Cubas et al., 2022; Shreve & Cloos, 1986). Subducted sediments further contribute to arc activity: the metamorphism of sediments also contributes to water release in subduction zone, leading to more arc activity (e.g., Hacker, 2008).…”

Fractal Distribution of Subduction‐Related Crack‐Seal Veins (Schistes Lustrés, W. Alps): Implications for Fluid Flow and Rupture Processes at the Downdip End of the Seismogenic Zone

“…The metasedimentary fraction, known as the Schistes Lustrés (e.g., Agard et al, 2001) dominates in the blueschist-facies LPU and LPM units (>90%), whereas the eclogite-facies units (LPL) are richer in mafic-ultramafic rocks (>40%; Herviou et al, 2022). The similarity between the peak burial depths of the LPU, LPM, and LPL units and those inferred for tectonic slicing and underplating, in both modern and fossil subduction zones, points to specific mechanisms controlling transient changes in interplate coupling at these depths (Agard et al, 2018;Cubas et al, 2022;Herviou et al, 2022;Plunder et al, 2015).…”