Prior and future earthquake effects in Valdivia, Chile

The 1960 M w = 9.5 subduction earthquake that struck Chile had an epicenter close to the city of Valdivia. There was widespread damage due both strong ground shaking from the earthquake and from the subsequent tsunami. These earthquake effects are examined from a modern perspective and the potential for future effects are discussed. Based on recent cone penetration measurements (sCPTu) the ground failures observed along the waterfront and other locations in Valdivia are attributed to cyclic failure of sensitive “clayey” soils and/or liquefaction of saturated “sandy” soils. If similar strong shaking is experienced in future earthquakes, similar ground failures would be expected. The regional subsidence in and around Valdivia following the 1960 earthquake is attributed to tectonic deformations and is corroborated with the same mechanism from the recent 2010 M w = 8.8 earthquake. If a similar magnitude event is experienced in the future, similar subsidence/uplift are expected which appear to follow a harmonic function. The goal of investigating these past earthquake effects and potential future effects is to help minimize the earthquakes risks in Valdivia and other regions subjected to the same hazards.