The 2010 Chile earthquake ruptured only part of the plate interface segment that had been accumulating tectonic stress since an earthquake in 1835, concludes a study online this week in Nature Geoscience. This finding suggests that last year’s earthquake did not eliminate seismic hazard risk in the region, and might even have increased it.

Stefano Lorito and colleagues use tsunami data and geodetic observations to derive an understanding of plate movement in the region of the earthquake. They find that during the 2010 Chile earthquake, slip occurred mainly to the north of the plate interface section that had remained unbroken since 1835, with a secondary concentration of slip to the south of that region.

Although the occurrence of a large earthquake off Chile did not come as a surprise, the researchers report that the exact location and extent were unexpected.