INQUA intensity Scale Evaluation for the 1980 Southern Italy "Historical" Earthquake
by
Eliana Esposito
IAMC-CNR, Napoli
Coauthors: S. Porfido, IAMC-CNR, Napoli; L. Guerrieri, APAT, Roma; E. Vittori, APAT, Roma; M. Pennetta, Università Federico II, Napoli

Within the framework of INQUA (International Union for Quaternary Research) activities, an important topic regards the "INQUA EEE Scale" (Michetti et al., 2004) for assessing earthquake intensities based only on the seismically-induced ground effects in natural environment (EEE stands for Earthquake Environmental Effects).

To improve the INQUA EEE Scale reliability, moderate-to-strong earthquakes, worldwide, are being analyzed by various working groups, in order to compare the obtained intensity values with those assessed with conventional scales (such as MM, MCS, MSK, EMS, JMA).

To this aim, we present here the revision and reinterpretation of the geological effects produced by the November 23rd 1980, Irpinia-Basilicata (Southern Italy) earthquake (Ms=6.9 NEIC, nucleation depth 10-12 km, epicentral intensity I0=X MCS), collected in the field soon after the event by several multidisciplinary groups (e.g., Carmignani et al., 1981), including some of the authors (EE and SP). The earthquake was a complex event, involving at least three distinct rupture episodes on different fault segments in a time span of approximately 40 seconds (Westaway, 1993). Over 300 localities were damaged with the loss of about 3, 000 lives.

The earthquake induced primary and secondary effects distributed in an area of nearly 30, 000 km2 principally located in the Campania and Basilicata regions. Tectonic surface ruptures, soil cracks, landslides, liquefaction, deep seated gravitational deformations and hydrological anomalies were observed.

After 20 years, we have decided to analyze the original evidence collected in the field by a) reviewing about 100 scientific papers, and b) performing new air photo interpretation, field surveys and interviews of eye witnesses. As a result, we have identified the most likely source of the 40 seconds event (Blumetti et al., 2002) and revealed the occurrence of numerous undocumented secondary effects (Esposito et al 1998, Porfido et al., 2002).

Coseismic surface faulting occurred over a length of almost 40 km, with a normal maximum displacement to the NE nearing 1 m at Mt. Marzano. A second rupture about 8 km long occurred ca. 40 seconds later on a SW dipping fault system between Muro Lucano and Santomenna with a maximum observed offset of 30 cm.

More than 200 landslides (mostly rock falls and pre-existing rotational and slump earth flows) were triggered over an area of 22, 000 km2, with single volumes sometimes exceeding 1 million cubic m.

Ground cracks were also widespread in the epicentral area, as well as liquefaction phenomena, although the latter were generally modest in size. Hydrologic anomalies were reported even very far from the epicentre, in zones of low macroseismic intensity (IV MCS).

The application of the INQUA EEE scale to the above listed coseismic effects has allowed to reconstruct an autonomous macroseismic field, to be compared with the MCS-MSK intensity field (Postpischl et al., 1985).

The analysis of the most recent strong "historical" earthquakes in Italy based on the INQUA EEE scale serves as a test of the approach to be adopted to improve the comparability of the many older earthquakes listed in the Italian seismic catalogue.

References

Blumetti A. M., Esposito E., Ferreli L., Michetti A.M., Porfido S., Serva L., Vittori E., (2002): New data and reinterpretation of the november 23, 1980, M 6.9, Irpinia-Lucania earthquake (Southern Apennine) coseismic surface effects. International Workshop "Large-scale vertical movements and related gravitational processes" Special Issue, Studi Geologici Camerti, . 2002, 19-27.

Carmignani, L., Cello, G., Cerrina Feroni, A., Funiciello, R., Kalin, O., Meccheri, M., Patacca, E., Pertusati, P., Plesi, G., Salvini, F., Scandone, P., Tortorici, L., and Turco, E.: 1981, Analisi del campo di fratturazione superficiale indotto dal terremoto campano-lucano del 23/11/1980, Rend. Soc. Geol. It. 4, 451-465.

Esposito, E., Gargiulo, A., Iaccarino, G., and Porfido S.: 1998, Distribuzione dei fenomeni franosi riattivati dai terremoti dell'Appennino meridionale. Censimento delle frane del terremoto del 1980, Proc. Conv. Int. Prevention of Hydrogeological Hazards: The Role of Scientific Research, 1, CNR-IRPI, Alba, 409-429.

Michetti A. M., E. Esposito, Gürpinar, J. Mohammadioun, B. Mohammadioun, A., S. Porfido, E. Rogozhin, L. Serva, R. Tatevossian, E. Vittori, F. Audemard, V. Comerci, S. Marco, J. McCalpin, N.A. Mörner. (2004): The INQUA Scale. An innovative approach for assessing earthquake intensities based on seismically-induced ground effects in natural environment. Special paper APAT, Mem. Descr. Carta geol. d'Italia , Vol LXVII. (E. Vittori & V. Comerci eds.).

Porfido S., Esposito E., Michetti A. M., Blumetti A.M., Vittori E., Tranfaglia G., Guerrieri L., Ferreli L., Serva L., (2002): The geological evidence for earthquakes induced effects in the Southern Apennines (Italy). Surveys in Geophysics, 23, 529-562.

Postpischl, D., Branno, A., Esposito, E., Ferrari, G., Marturano, A., Porfido, S., Rinaldis, V., and Stucchi, M.: 1985, The Irpinia earthquake of November 23, 1980, in Atlas of Isoseismal Maps of Italian Earthquakes, CNR-PFG 114(2B), 152-157.

Westaway, R.: 1993, Fault rupture geometry for the 1980 Irpinia earthquake: a working hypothesis, Annali di Geofisica 36(1), 51-69.

Date received: July 8, 2005

Copyright © 2005 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caqy-24.