Liquefaction evidence in the Chilean subduction zone

Montalva, Gonzalo A.; Ruz, Francisco

Keywords: chile, subduction, liquefaction, overprediction


Recent megathrust events in Chile have provided the engineering community, with case studies that allow the evaluation of current state of practice regarding liquefaction surface manifestation. A liquefaction triggering assessment is conducted using several of the most widely used methodologies, to analyze how well the current state of the art matches the observed evidence in subduction earthquakes that have long duration and high intensities. Field observations of more than 60 sites show a mismatch between observed and predicted liquefaction behavior during the 2010 Mw 8.8 Maule and the recent 2015 Illapel Mw 8.3 earthquakes. Results show that Shear Wave velocity methodologies are worst than SPT methodologies. We speculate on the reasons for these differences. Partial drainage during the strong shaking could lead to a frequency dependence of the liquefaction behavior, we concur with studies that suggest that soil stiffness (i.e., shear-wave velocity or site period) are relevant parameters to be included. For the case of large megathrust events and the sites within this dataset, existing methodologies have a tendency to overpredict liquefaction triggering. A simplified methodology to assess the surface manifestation of liquefaction in Concepción is presented as an alternative for subduction induced liquefaction triggering assessment. We conclude that more research is needed in this relevant issue.

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Fecha de publicación: 2017