Site effects associated with the 2010 maule earthquake in zones characterized by the presence of wetlands in the Biobio Region, Chile

Abstract

After 2010 Maule (Chilean) earthquake (Mw=8.8, February 27th) some residential areas located along the coastal border in southern Chile and close to water bodies and wetlands showed extensive damage in housing, streets, electric, water, and gas lines. That was the case of the neighborhoods Villa Las Araucarias (Arauco) and Bayona (San Pedro), situated 100 – 170 km south of the epicenter zone, and established on top of a porous artificial filling and compacted soils. Conversely, in other sites soils and infrastructure remained intact. Here, we present a study that aimed to describe and assess the effects of the Maule earthquake on urban sites. We tried to disentangle the differences between damaged and undamaged zones by identifying modes of damage as well as by detecting geophysical anomalies associated with such a divergent behavior. For this reason, we also analyzed three undamaged zones: Colcura (Lota), Laguna Grande (San Pedro) and Los Canelos (San Pedro). Results suggest that the damaged locations beha- ved as examples of the liquefaction phenomenon, triggered by a large ear- thquake. The implications of this finding are discussed according to exis- ting Chilean regulation in terms of the so-called VS30 parameter as a quality factor for soils. We also discuss different aspects related to the relationship between geophysical methodologies applied here, visual observations and geological/soil interpretation.