Georg GANGL
(University of Vienna, Austria)
Keywords: 1895-Lubljana earthquake, macroseismic damage
Abstract:
Franz E. Suess (1867-1941) was appointed as a young geologist by his employer the Imperial Geological Survey in Vienna to explore the Ljubljana earthquake of April 14, 1895, immediately after the earthquake event had taken place and to describe it in detail. Quite different from his father Eduard Suess, he used a pragmatic approach and laid down many significant observations. Based on the observations and in particular on the local damage degree, he plotted a “pleistoseismic map” with intensity data Points. Franz E. Suess is impressed by the damage in Ljubljana and in the surrounding villages. He recognized the influence of the loose substratum on the high damage caused.
Franz E Suess recognized already 1895 the relationship between the degree of damage and the kind of foundation soil of buildings. The event is included in the modern catalogue “CFTI4Med” Further contemporary publications are cited by ALBINI et al., 2014 as well as additional data points, where the earthquake was felt.
To classify the damage Franz E. Suess used one of the first macroseismic scales of Forel, a previous version of the later Rossi-Forel scale (1882) to characterize the local earthquake vibration. As a consequence of the damaging earthquake, an earthquake Commission was established by the Austria-Hungary monarchy, in which earthquake events were treated by officials in charge of each “crown land” (province of the monarchy).
The scientific assessment of historical earthquakes is essential for the earthquake research (risk evaluation). If we want to obtain information on the earthquake activity of past centuries; the immediate description of the past events is available, from the 1895 earthquake numerous photographs exist too (NUK 1995), allow to estimate the degree of damage and the intensity of the vibration by the latest macroseismic scale (European Macroseismic Scale <EMS98>), by which the maximal intensity of degree 9 was reached. The intensity should be distinguished from the magnitude value of an earthquake, which characterizes the energy of an event, calculated from instrumental data of seismograms and does not describe how it is felt and the local effect of destruction. The scientific publications and maps of the last decades of the monarchy are a valuable basis for the evaluation of historic sources, which were the basis of modern earthquake catalogues and future classification and processing. See literature cited on the poster.