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Vertical deformation through a complete seismic cycle at Isla Santa María, Chile

June 18, 2015

Individual great earthquakes are posited to release the elastic strain energy that has accumulated over centuries by the gradual movement of tectonic plates12. However, knowledge of plate deformation during a complete seismic cycle—two successive great earthquakes and the intervening interseismic period—remains incomplete3. A complete seismic cycle began in south-central Chile in 1835 with an earthquake of about magnitude 8.5 (refs 45) and ended in 2010 with a magnitude 8.8 earthquake6. During the first earthquake, an uplift of Isla Santa María by 2.4 to 3 m was documented45. In the second earthquake, the island was uplifted7 by 1.8 m. Here we use nautical surveys made in 1804, after the earthquake in 1835 and in 1886, together with modern echo sounder surveys and GPS measurements made immediately before and after the 2010 earthquake, to quantify vertical deformation through the complete seismic cycle. We find that in the period between the two earthquakes, Isla Santa María subsided by about 1.4 m. We simulate the patterns of vertical deformation with a finite-element model and find that they agree broadly with predictions from elastic rebound theory2. However, comparison with geomorphic and geologic records of millennial coastline emergence89 reveal that 10–20% of the vertical uplift could be permanent.

Publication Year 2015
Title Vertical deformation through a complete seismic cycle at Isla Santa María, Chile
DOI 10.1038/ngeo2468
Authors Robert L. Wesson, Daniel Melnick, Marco Cisternas, Marcos Moreno, Lisa Ely
Publication Type Article
Publication Subtype Journal Article
Series Title Nature Geoscience
Index ID 70190054
Record Source USGS Publications Warehouse
USGS Organization Geologic Hazards Science Center