A comparison of CPTu and SDMT at Garza and Ostional beaches in the aftermath of the Sept 5 2012 Samara Earthquake, Costa Rica: liquefaction case studies

On September 5, 2012, a strong Mw = 7.6 earthquake hit Costa Rica. Its epicenter was located 10 km south of Samara, Guanacaste (offshore). This motion induced several geotechnical effects such as landslides, liquefaction, lateral spreading and local amplification. Of particular interest to the present paper was the occurrence of lateral spreading along several beaches located nearby the epicenter. The authors considered this a valuable opportunity to better understand this type of geotechnical phenomena. Contacts were made with the local governments in order to get access permits to two public beaches (Ostional and Garza). CPTu, SDMT, and disturbed sampling were carried out in order to gain an understanding of the geotechnical conditions that favored the occurrence of liquefaction. The aim of this paper is to use the latest methods for evaluating liquefaction potential based on SDMT and CPTu to back predict the observed phenomena and consequences. The main idea is to compare CPTu and SDMT as predictors of liquefaction for specific case studies.