Case History
Geotechnical damage caused by the 2010 Maule, Chile earthquake
Susumu Yasuda, Tokyo Denki University, Japan
Ramon Verdugo, Universidad de Chile, Chile
Kazuo Konagai, University of Tokyo, Japan
Takahiro Sugano, Port and Airport Research Institute, Japan
Felipe Villalobos, Universidad Catolica de la Santisima Concepción, Chile
Mitsu Okamura, Ehime University, Japan
Tetsuo Tobita, Kyoto University, Japan
Andres Torres, Universidad de Chile, Chile
Ikuo Towhata, University of Tokyo, Japan
1. INTRODUCTION
The country of Chile is located along the subduction of Nazca tectonic plate, that is moving at the rate of 7 cm/year , against South America. Consequently, many gigantic earthquakes have affected this country in the past. For example, the event in 1960 registered 9.5 in magnitude and caused significant damage in its south part including Valdivia. Another event in 1985 was of magnitude of 7.8 and affected the central part of the country where Valparaíso and San Antonio are situated (Troncoso, 1989).
On February 27th, 2010, the Maule earthquake of 8.8 in moment magnitude occurred in a region between those two former earthquakes. The epicenter was located near Cobquecura. The length of the seismogenic fault was estimated to be around 450 to 500 km along the Pacific Coast. This means that Santiago, the capital, and Valparaíso are located near the north boundary of the fault, while Concepcíon near the south end. Cities in the affected area are situated either in the central valley (Quaternary geology in Fig. 1) or along the Pacific Coast. Buildings, houses, bridges, road embankments, tailing dams and other structures were damaged by the earthquake. Figure 1 illustrates the geological condition in the affected area. The coastal mountain range along the Pacific Ocean are covered by Tertiary deposits, while Andes Mountains, which is parallel to the coast, is made of Tertiary and earthquake older rocks. The central valley between these two mountain ranges has a deposit of Quaternary soil. Quaternary soil deposit is also found in several lowlands along the Pacific Coast. However, those lowlands are very small except the one around Concepción.
A cold sea current in the Pacific Ocean makes the climate in the affected region relatively dry. In particular, the northern part receives less recipitation than the southern part. Typically, the average annual rainfall in Santiago is only 350 mm/year.
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