On the South Iceland earthquakes in June 2000: strong-motion effects and damage

The South Iceland earthquake sequence in June 2000 is discussed using available recordings from the Icelandic Strong-motion Network. The two largest events in the sequence occurred on 17 and 21 June, with surface-wave magnitudes of 6.6 and 6.5, respectively. Both were shallow, right-lateral, strike slip earthquakes on north-south striking faults. The attenuation of strong ground motion is analysed in terms of Arias intensity, rms and peak ground acceleration. Special emphasis is placed on near-source effects, as the shortest distances to the causative fault for recording stations are no more than a few km. The recorded near-source time series are characterised by very high acceleration but short duration. Furthermore, earthquake response spectra are discussed, both elastic and inelastic, emphasising strength and ductility demand. These spectra are viewed in the perspective of current seismic code as well as with respect to the observed earthquake-induced damage. The earthquake sequence in 2000 is also compared with noteworthy historic earthquakes in South Iceland, namely those in 1896 and 1912. The comparison is based on the total seismic moment and the size of the damage areas. The similarity between the 1896 and 2000 events is remarkable. In view of this and the high acceleration encountered, the damage in the epicentral areas is less than might have been expected. This is partly due to preparedness undertaken by individuals, municipalities and companies.