ナスカプレート
Chile lies above a convergent plate boundary, an area where the Nazca Plate under the Pacific Ocean is subducted or moved beneath the South American Plate. In the region around Valparaiso, the rate of convergence is about 70 mm/yr. As these two plates converge, it drives the Nazca plate with massive movements called megathrust earthquakes. The 1906 event was one of many large earthquakes in Chile along this plate boundary. Earthquakes can originate at the plate interface itself or within either the subducting or overriding plates.