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G. Monachesi, Osservatorio Geofisico Sperimentale di Macerata R. Camassi, GNDT at UR DISTART, Engineering Faculty, University of Bologna D. Molin, SSN Servizio Sismico Nazionale |
From 26 September on, the National Group for Defence against Earthquakes (GNDT), the National Seismic Survey (SSN) and the National Institute of Geophysics (ING) carried on a joint macroseismic survey with the aim of achieving both a preliminary evaluation of the maximum earthquake effects and a delimitation of the damaged area.
As usual, macroseismic data have been gathered mostly by means of field investigation of the affected areas; however, due to the significant extension of the damaged and felt areas, for some localities information was taken from press reports or collected by means of telephone interviews and contacts with experts and technicians.
From 3 October on, a more detailed survey was started in the most damaged localities, with the following aims:
After some damaging aftershocks new surveys were carried out on 8 and then from 16 to 19 October, particularly in the areas of Sellano, Preci, Alta Val Nerina and Alto Maceratere.
In the following, the intensity distribution as available up to 20 October is presented (Table 1), including maps where intensities are shown with reference both to localities (Fig. 1) and communes (Fig. 2); the intensity in a commune was estimated as the maximum intensity evaluated in at least one locality inside its territory.
It has to be stressed that the intensity distribution represents, as far as possible, the cumulative effects of the shocks occurred in September and October 1997.
Intensity estimates may be affected by some uncertainties; further on, not all the damaged localities were surveyed so far; therefore, some of them could be not yet included in the annexed list.
Finally, it has to be stressed that data on many localities, especially those slightly damaged by the first events might be not up-to-date.
However as of today, local and regional administrations and the Joint Operative Center (Centro Operativo Misto - COM) as well do have in their hands data and information more detailed than those which this survey is based on. Such data are therefore the most suitable to compile a damage classification list. A comparison with the data collected by engineers is foreseen for the next weeks.
Survey and data management was performed by:
P. Albini, H. Alinaghi, R. Azzaro, M.S. Barbano, R. Camassi, C. Carocci, V. Castelli, H. Coppari, E. Cova, E. Ercolani, M. Frapiccini, I. Leschiutta, C. Meletti, F. Meloni, G. Monachesi, G. Morelli, A. Moroni, M. Mucciarelli, M. Onida, S. Raccichini, M. Stucchi, A. Zerga (GNDT)
P. Galli, A. Lisi, G. Martini, D. Molin, M. Rebuffat, P. Soddu (SSN)
S. Del Mese, C. Gasparini, A. Massucci, A. Tertulliani, M. Vecchi (ING)
I. Cecic (Geophysical Survey of Ljubljana, Slovenja)