Three and a half hours into Feb 27, 2010, a mega-earthquake with a moment magnitude (Mw) registering 8.8 on the Richter scale shook the central-south part of Chile. With its epicenter estimated at 43 km offshore and northwest of the locality of Cobquecura (see Fig. 7) and nearly 400 km southwest of Santiago, it produced 8.5 magnitude recordings in the greater Santiago city area; Chile’s capital, most populous city (population of around 6 million) and home to numerous tall glass facade buildings.
This “megathrust" earthquake occurred at the convergence of the Nazca (oceanic) plate with the South American continental plate at a depth of 35 km (21.7 miles) [source: Servicio Sismologico, University of Chile, www. sismolo – gia. cl]. “Megathrust earthquakes occur at subduction zones at destructive plate boundaries (convergent boundaries), where one tectonic plate is forced under (subducts) another. Due to the shallow dip of the plate boundary, which causes large sections to get stuck, these earthquakes are among the world’s largest, with moment magnitudes that can exceed 9.0. Since 1900, all six earthquakes of magnitude 9.0 or greater have been megathrust earthquakes. No other type of known tectonic activity can produce earthquakes of this scale" .