5 May 2014 MW 6.1 Mae Lao (Northern Thailand) earthquake: Interpretations of recorded ground motion and structural damage

Abstract

A moderate left-lateral strike-slip earthquake of MW 6.1 occurred on 5 May 2014 in northern Thailand, causing damage to the town of Mae Lao and nearby municipalities. Based on an instrumental earthquake catalog, the Mae Lao earthquake is the second largest earthquake in modern Thai history after the MW 6.3 Nan earthquake in 1935. In this study, the strong-motion records from the epicentral area are analyzed in order to investigate the characteristics of the ground motions. In addition, post-earthquake field observations and statistics for typical structural damage in the affected area, such as the soft story effect and the shear failure of columns, are summarized. Besides major structural damage, the majority of structures in the epicentral area withstood the strong motion, which could be due to the low stress drop of the main shock (40 bars) leading to below average ground motions for an MW 6.1 earthquake.