No recorded human generation in Chile has escaped the damaging consequences of large earthquakes. More than ten events with magnitudes equal to or greater than magnitude 8 have taken place during the twentieth century alone. Among these earthquakes is the 1960 event, the largest earthquake ever recorded since the beginning of instrumental seismology. Such extreme seismic activity is a result of the interaction of the Nazca, Antarctic, Scotia and South American plates in southwestern South America where Chile is located (Fig. 10.1)
The large thrust earthquakes, responsible for most of the damage recorded in history, are located along the coast from Arica (18°S, the northernmost extreme of coastal Chile) to the triple-junction at Taitao Peninsula (46°S). With magnitudes that can reach values well over eight, these events are usually accompanied by noticeable coastal elevation changes and, depending on the amount of seafloor vertical displacement, by catastrophic tsunamis. Their rupture zones are limited to the coupled region between the Nazca and South American plates which extends down to 45–53 km depth (Tichelaar & Ruff 1991) and their lengths could reach well over 1000 km. Their spatial and time characteristics have been studied (Kelleher 1972; Barrientos 1981; Martin 1991; Nishenko 1985; Ramírez 1988; Beck et al. 1998), so that the hazard due to these large events is well recognized and understood. Return periods for magnitude 8 events are of the order of 80 to 130 years for any given region in Chile, but about 12
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This book is the first comprehensive account in English of the geology of Chile, providing a key reference work that brings together many years of research, and written mostly by Chilean authors from various universities and other centres of research excellence. The 13 chapters begin with a general overview, followed by detailed accounts of Andean tectonostratigraphy and magmatism, the amazingly active volcanism, the world class ore deposits that have proven to be so critical to the welfare of the country, and Chilean water resources. The subject then turns to geophysics with an examination of neotectonics and earthquakes, the hazardous frequency of which is a daily fact of life for the Chilean population. There are chapters on the offshore geology and oceanography of the SE Pacific Ocean, subjects that continue to attract much research not least from those seeking to understand world climatic variations, and on late Quaternary land environments, concluding with an account examining human colonization of southernmost America.
During his voyage on H.M.S. Beagle, an extended visit to Chile (1834-35) had a profound impact on Charles Darwin, especially on his understanding of volcanoes, earthquakes and tsunamis. Over more recent decades scientists have come to recognize the Chilean Andes as providing the classic example of a mountain belt produced by oceanic subduction beneath a continent, as well as some of the most dramatic scenic and climatic variations on Earth. In the final chapter, the editors offer a description of a drive from the Mediterranean landscapes of central Chile to the hyperarid Atacama Desert, a contribution designed to give visitors a chance to experience for themselves the geology and scenery of this extraordinary country.