Using the INQUA scale for the assessment of intensity: Case study of the 2003 Lefkada (Ionian Islands), Greece earthquake

A new scale has been introduced by the INQUA Subcommission on Paleoseismicity for evaluating the intensity of an earthquake by examining the earthquake environmental effects. The definitions of the intensity degrees, provided by the INQUA scale, are based solely on the ground effects such as liquefaction, rockfalls, and ground fissures. The Lefkada (western Greece) earthquake of 2003 (Mw=6.2, Ms=6.4) has been selected as a case study for testing the accuracy and reliability of the INQUA scale. The evaluated intensity parameters of the 2003 earthquake based on the MM and EMS scales are compared, with the one assessed using the “INQUA intensity” scale. Furthermore, these degrees of “INQUA intensity” were compared with the values of intensity of past events. From this comparison, we conclude that in Greece, in urban areas developed according to the provisions of the upgraded seismic codes, the evaluated intensities based on EMS scale may underestimate the ground shaking. In order to assess accurately the seismic hazard of an area, the use of the INQUA scale in combination with the EMS scale is suggested.