Coseismic uplift as strandplain-building mechanism: morphodynamic and stratigraphic evidence from the 2010 Maule earthquake, south-central Chile

Cristian Araya-Cornejo , Diego Aedo, Carolina Martínez, Daniel Melnick, César Araya, Matías Carvajal, Arturo Belmonte, Marcos Moreno, Jorge Qüense

Coseismic uplift along convergent margins drives rapid coastal progradation, yet its short-term morpho-stratigraphic response remains poorly documented at human timescales. Here we integrate four complementary high-resolution proxies: satellite-derived shorelines, multi-temporal mapping of the seaward dune vegetation line (SVDL), ground-penetrating radar stratigraphy, and UAV–LiDAR topographic surveys to reconstruct 15 years of post-seismic coastal evolution at Laraquete–Horcones Beach following the 2010 Mw 8.8 Maule earthquake. Pre-seismic records confirm a sediment-starved coast lacking long-term progradation. The earthquake produced an instantaneous shoreline advance of 25 ± 4.9 m, followed by sustained post-seismic SVDL progradation of 45–48 m. This distance closely matches the mean inter-ridge spacing of the adjacent Holocene Laraquete–Carampangue strandplain (48.9 m). GPR data reveal a replicable prograding beach–berm stratigraphic succession (PBF→BBF), locally capped by an aeolian drape, with abrupt landward signal attenuation indicating rapid coastal abandonment and subaerial stabilization. By integrating short-term morphodynamics with subsurface stratigraphy, these results provide the first multi-proxy observational evidence consistent with repeated coseismic uplift driving Holocene strandplain construction along sediment-limited convergent margins, supporting this mechanism as a first-order control in sediment-starved convergent settings. Coseismic uplift thus functions as a recurring tectonic buffer, temporarily offsetting sediment deficits and interseismic subsidence, with implications for coastal resilience under sea-level rise.