A saga of the 1896 South Iceland earthquake sequence: magnitudes, macroseismic effects and damage

Abstract

This paper describes Professor Ambraseys’s work on the quantification of magnitudes of the main events in the 1896 South Iceland earthquake sequence, using original teleseismic data recorded by primitive seismological instruments located in Russia and Italy. This includes an example of his original worksheets showing surface-wave magnitude re-appraisal along with the initial part of the parametric earthquake catalogue of Iceland. A brief description of the macroseismic effects of the earthquake sequence is presented. Earthquake damage to buildings in the most affected area is quantified as fractions of collapsed farmhouses. Spatial distribution of the quantified damage shows good correspondence to the estimated epicentres of the earthquakes of the sequence. The macroseismic effects of the earthquake sequence are described and compared to those of the South Iceland earthquakes in June 2000 and May 2008. It is argued that the magnitude estimate of the largest event of the sequence as obtained by Professor Ambraseys, based entirely on teleseismic measurements, is likely to be more accurate than other estimates based on the extent of the damaged area. This argument is supported by a discussion based on a comparison between the felt area, damaged area, and seismic moment estimates of the June 2000 earthquakes with the documented effects of the 1896 main shock. The observations and discussions presented here highlight the importance of Professor Ambraseys in the study of historic earthquakes.