I terremoti del XIX secolo dell'Appennino Campano-Lucano

Article (PDF Available)inBollettino- Societa Geologica Italiana 41 · January 1998with 180 Reads
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  • Book
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    The debate originated within the Workshop of the Subcommission on Paleoseismicity held during the XV INQUA Congress in Durban, August 1999, emphasized the importance of developing a multi-proxy empirical database on earthquake ground effects that can be used by, and incorporated into, seismic-hazard assessment practices. The Subcommission selected this task as the primary goal for the past inter-congress period. An interdisciplinary Working Group (WG) was established, including geologists, seismologists and engineers, in order to formalize the collected data into a new scale of macroseismic intensity based only on ground effects: the proposed INQUA scale. This paper illustrates the results of the research conducted by the WG, introduces the proposed INQUA scale, and discusses major issues related to this innovative approach to the intensity assessment. The INQUA scale first draft is due to Leonello Serva, based on the compilation and comparison of the three most commonly used intensity scales, i.e., the Mercalli-Cancani-Sieberg (MCS), Medvedev-Sponhouer-Karnik (MSK) and Mercalli Modified (MM). Eutizio Vittori, Eliana Esposito, Sabina Porfido and Alessandro M. Michetti produced a revised version, after (a) integration with the revised MM scale of Dengler and McPherson (1993) and (b) checking the scale against the description of coseismic ground effects and intensity assessments for several tens of historical and instrumental earthquakes in the world. This version of the INQUA scale, presented during the XVI INQUA Congress in Reno, July 23-30, 2003, is a joint contribution of the WG including new data, editing, comments and scientific discussion from Bagher and Jody Mohammadioun, Eugene Roghozin, Ruben Tatevossian, Aybars Gürpinar, Franck Audemard, Shmulik Marco, Jim McCalpin, Nils-Axel Mörner, and Valerio Comerci. At this stage, the newly revised MM scale for New Zealand (Hancox, Perrin and Dellow, 2002), kindly provided by Graeme Hancox, has been also taken into account. The outstanding progress of paleoseismological and Quaternary geology research in the past decades makes available an entirely new knowledge for understanding the response of the physical environment to seismicity, thereby providing the basis for the proposed INQUA intensity scale. The INQUA scale allows to define the epicentral intensity starting from the VI – VII level, with increasing accuracy going towards the highest levels. In the intention of the WG, the INQUA scale should not be used alone, but in combination with the existing scales. In the intensity range up to IX – X the scale allows a comparison between environmental effects and damage indicators, emphasizing the role of primary tectonic effects, which are independent from the local economy and cultural setting. In the intensity range X to XII, the INQUA scale is arguably the only suitable tool for assessing the epicentral intensity. In summary, we regard the INQUA scale as an unreplaceable addition to all the existing scales up to the IX – X level, while it represent the substance of the epicentral intensity assessment for the highest degrees.
  • Article
    Identification of an active fault and the local versus regional present-day stress field in the Irpinia region (southern Apennines) have been performed along a 5900 m deep well (San Gregorio Magno 1) by a detailed breakout and geophysical log analysis. The selected area is characterized by diffuse low magnitude seismicity, although in historical times moderate to large earthquakes have repeatedly struck it. On 23rd November 1980 a strong earthquake (M = 6.9) nucleated on a 38-km long normal fault, named Irpinia fault, producing the first unequivocal historical surface faulting ever documented in Italy. The analysis of stress-induced wellbore breakouts shows a direction of minimum horizontal stress N18°±24°, fairly consistent with the regional stress trend (N44°±20°). The small discrepancy between our result and the regional stress orientation might be related to the influence of local stress sources such as variations of the Irpinia fault plane orientation and the presence of differently oriented active shear zones. This paper shows for the first time a detailed analysis on the present-day stress along a well to identify the Irpinia fault at depth and constrain its geometry.
  • Article
    Most relevant macroseismic and instrumental data concerning past and current seismic activity of the Potentino, southern Italy, have been collected in order to study the seismic behaviour of this area.Ten among the most important recent and historical earthquakes occurred in the area from 1826 to 1990 have been studied by means of macroseismic methodologies; macroseismic fields for all the events indicate a general isoseismal lengthening in the direction of the Apennines chain (northwest-southeast), a rapid attenuation of intensity westward of the studied area and a strong propagation eastwards; this configuration is strongly dependent on the source mechanisms of the seismic events and the geological dishomogeneities of the concerned areas.As regards earthquakes which have been instrumentally recorded in the Campania-Basilicata area from 1980 to 1991, more than 1300 accurate hypocentral locations have been computed for events with MD ⩾ 2.5, using data from Osservatorio Vesuviano (O.V.) and Istituto Nazionale di Geofisica (I.N.G.) seismic networks.Special emphasis is put on the Potenza May 5, 1990 earthquake (MS = 5.4 NEIC—National Earthquake Information Center; I = VII MSK) which was the strongest recent event in the area and was felt in a large sector of southern Italy. As regards the seismic sequence following this event, about 110 aftershocks with MD ⩾ 1.9 have been located very close to the town of Potenza, northeast of it, with a clustering-type space distribution. The occurrence of the events is strongly time concentrated, in so defining a main shock-aftershocks typical sequence. Moreover, the macroseismic investigation of the main event has allowed to map out isoseismal lines bounding VII, VI, V and IV MSK areas; the isoseismals pattern shows that attenuation and amplification of intensity are observed in the same areas as for the previous events.Beginning from May 26, 1991 an increase of seismicity, initiated by an earthquake of ML = 4.7 NEIC and I = VI-VII MSK was observed nearly in the same area as the 1990 sequence. Accurate locations of 84 events with MD ⩾ 1.9 have been computed. However, this sequence seems to have a slightly different character from the 1990 one, in that events are scattered in time and seismic energy release is comparable to a swarm-type seismic sequence.As regards the previous sequences, fault plane solutions for the highest-magnitude events and for appropriate groups of events have been worked out; the mechanisms indicate normal faulting motion with T axes oriented orthogonal to the Apenninic chain.In conclusion, detailed analyses on the historical and recent seismicity of the Potentino area and adjacent ones have allowed to identify at least four seismogenic zones which show activity with different features. Such zoning represents a contribution to the seismic hazard assessment in the Southern Apennines on a regional scale.
  • Data
    La prima versione disponibile al pubblico del Database Macrosismico Italiano risale al maggio 2007 (DBMI04; Stucchi et al., 2007). Esso conteneva i dati di intensità utilizzati per la compilazione dei parametri del catalogo parametrico rilasciato nel maggio 2004 (CPTI04; Gruppo di Lavoro CPTI, 2004)), a sua volta utilizzato per la compilazione della Mappa di Pericolosità Sismica del territorio nazionale (MPS04, Gruppo di Lavoro MPS, 2004). Nel dicembre 2008 sono state pubblicate online le porzioni 1901-2006 del catalogo CPTI08 e del relativo Database Macrosismico DBMI08. Nel gennaio 2009 è stato avviato il completamento del catalogo e del database macrosismico, con riferimento alla porzione pre-1900. Questa operazione ha comportato anche un aggiornamento dei contenuti relativi alla finestra temporale già pubblicata. Alla data del 6 aprile 2009 il catalogo parametrico e il database macrosismico erano appena stati sottoposti all’ultima tornata di verifiche. Gli autori hanno allora ritenuto opportuno accelerare la pubblicazione di una porzione del catalogo e del Database Macrosismico, definite CPTI08aq (Rovida e Gruppo di Lavoro CPTI, 2009) e DBMI08aq (Locati e Gruppo di Lavoro DBMI, 2009), relative ad un’area comprendente la zona colpita dai terremoti dell’Aquilano, per consentire agli operatori impegnati nell’area di utilizzare dati aggiornati. Nel 2010 è stata pubblicata una versione aggiornata del database, denominata DBMI10beta, che copre la finestra temporale 1000-2006. Questa versione è stata resa disponibile ai ricercatori che operano nell’ambito di progetti dell’Istituto per un periodo di sperimentazione. Oggi viene rilasciata la terza versione pubblica denominata DBMI11, che raccoglie le osservazioni emerse nel corso del predetto periodo. Questa versione non contiene i risultati di alcuni sviluppi metodologici realizzati nell’ambito del progetto EC “SHARE” (Seismic Hazard Harmonization in Europe); inoltre, non utilizza ancora un considerevole quantitativo di nuove informazioni reso disponibile da: Molin et al. (2008); Camassi et al. (2011); la versione 2009 di ECOS (Faeh et al., 2011) e la versione 2010 di SisFrance (SisFrance, 2010). Questi elementi, unitamente ad altri sviluppi, verranno considerati per la prossima versione del database.
  • Article
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    The INQUA Scale, the new macroseismic intensity scale only based on earthquake environmental effects (EEE) that is described in this Report, is a multi-author undertaking, developed within the INQUA Subcommission on Paleoseismicity and under a close collaboration with APAT. The Scale has been presented during the XVI INQUA Congress, held in Reno, NV, USA, on July 23 to 30, 2003. Following the scientific discussion in this meeting, the Scale has been formally adopted for a trial time-window of 4 years (2003-2007), in order to present a new updated version at the next 2007 INQUA Congress in Cairn, Australia. The INQUA Scale, relying solely on modifications to the geological medium, has the potential to become a tool of prime importance for understanding the strength of seismic events, and therefore for mitigating the related environmental risks. Of course, such an intensity scale is intended to integrate the existing scales, not to replace them. In the practice of intensity assessment in the last 40 years or so very little advantage has been taken by the use of coseismic ground effects. The INQUA scale approach, instead, can encourage greater objectivity in the process of seismic intensity assessment through independence from the variable nature of man and his works, both for earthquakes of the historical and pre-historical periods and for those of today.
  • Article
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    On 9 September 1998, at 13:28local rime (11:28 UTC), a moderate earthquake of M w= 5.6 struck the Southern Apennines at the northwest margin of the Pollino Massif (the highest mountain range of the region, reaching elevations above 2,000 m a.s.l.; Figures l and 2). The macroseismic epicenter is located about 3 km southeast ofLauria, with a maximum intensity ofVIII on the MCS scale (or MM or MSK; see below far a correlation among macrosdsmic scales); thus we refer to this event as the Lauria earthquake. Historical towns-such as Lagonegro, Lauria, and Castelluccio-suffered signifìcant damage, in particular that of Rivello, which is a remarkable !oca! artistic site. Severa! ground effects followed the shock, and a rockfall on the road between Cersuta and Acquafredda (site 9a in Figure 3) claimed one !ife. A moderate magnitude event, the Lauria earthquake, together with the 5 May 1990 Potenza earthquake (M,= 5.4), was the largest earthquake in southern ltaly since the destructive 23 November 1980 lrpinia earthquake (Alessio et al., 1995, eu m bib.; Table l and Figure 2A). The day after the shock we initiated a reconnaissance survey of the epicentral area in arder to record the geologica! and environmental changes induced by the earthquake. Among many other effects, we observed the rejuvenation of a bedrock fau!t scarp. In this paper we focus o n this evidence of tectonic surface rupture because i t has signifìcant implications for the seismic hazard assessment both in (a) this sector of the Apennines and (b) other parts of the world.
  • Article
    Following the increase in seismic activity which occurred near Isernia (Molise, Central Italy) in January 1986, a digital seismic network of four stations with three-component, short-period seismometers, was installed in the area by the Osservatorio Vesuviano. The temporary network had an average station spacing of about 8–10 km and, in combination with permanent local seismic stations, allowed the accurate determination of earthquake locations during an operating period of about one month. Among the 1517 detected earthquakes, 170 events were selected with standard errors on epicentre and depth not greater than respectively 0.5 and 1.5 km. The most frequent focal depths ranged between 4 and 8 km, while the epicentres distribution covered a small area NE of Isernia of about 10 km2. A main rupture zone could not be clearly identified from the spatial distribution of the earthquakes, suggesting a rupture mechanism involving heterogeneous materials. The activity was characterized by low energy levels, the largest earthquake, on January 18, 1986, havingM D =4.0. The time sequence of events and pattern of seismic energy release revealed a strong temporal clustering of events, similar to the behaviour commonly associated with seismic swarms.
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