The Friuli earthquake (1976–1977)

Finetti, I.; Russi, M.; Slejko, D.

doi:10.1016/0040-1951(79)90070-2

Cited by 22 publications

(15 citation statements)

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“…All studies agree that the seismic sequence activated a thrust system source, dipping NNE at low angle. The main shock was associated by Finetti et al (1979) and Barbano et al (1985) with the Dinaric Buia‐Tricesimo fault (TF in Fig. 1).…”

Section: Seismotectonic Aspects Of the 1976—77 Friuli Seismic Sequencementioning

confidence: 91%

“…Because local seismic records are lacking, the location of the 1976 shocks has been investigated by a number of authors (Console & Gasparini 1976; Finetti et al 1979; Cipar 1980; Lyon‐Caen 1980; Zonno & Kind 1984; Slejko & Renner 1984; Slejko et al 1999) using teleseismic data and recordings from the other regional networks. So uncertainties in event locations, especially those relating to the main shock and other major events of the sequence, are mainly due to a lack of local data and also to the varying computational methods.…”

Section: Data Used For Modellingmentioning

confidence: 99%

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Changes in failure stress and stress transfer during the 1976-77 Friuli earthquake sequence

Perniola

Bressan

Pondrelli

2004

Geophysical Journal International

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S U M M A R YCoulomb stress changes related to the sequence of strong earthquakes that affected the Friuli area (Northeastern Italy) during the period 1976-77 have been investigated to explore the possibility of fault interaction and stress transfer mechanisms. The seismic sequence that followed the M w 6.4 mainshock of 1976 May 6, consists of 5 events of M w between 5.2 and 6.0 during the same year and one event of M w 5.3 that occurred in 1977 September, all characterized by thrust focal mechanisms. The area is affected by a regional compressive stress, which tends to activate N-dipping thrust planes. The goal of this study is to analyse and verify the relationship between the stress changes induced by the mainshock and the occurrence of subsequent events. Our results show that the mainshock induced a variation in the stress field in the area where most of the seismic events occurred. Our modelling shows a positive correlation between the areas of increased Coulomb stress induced by the mainshock and the distribution of seismicity that followed. This evidence suggests stress interaction and the possibility that the mainshock promoted the rupture of those faults associated with the event of 1976 May 9 (M w 5.1) and the events of 1976 September 11 (M w 5.2 and 5.6), 1976 September 15 (M w 6.0) and 1977 September 16 (M w 5.3). The Coulomb stress caused by co-seismic dislocations decreased in the zone where an M w 5.9 earthquake occurred on September 15 at 03:15. When we included the contribution of the regional tectonic loading in the calculation of Coulomb stress changes, we found a positive correlation between the hypocentral area of the September 15 03:15 event and the area of Coulomb stress increase. Aftershocks that occurred after the mainshock but before the September 15 03:15 event are also located in the area of Coulomb stress increase.The Friuli seismic sequence which started on 1976 May 6 (at 20:00) with a mainshock of M w 6.4 was the most important that affected Northeastern Italy during the 20th century. The maximum intensity, measured using the Medvedev-Sponheuer-Karnik scale, was X. The sequence displayed some interesting peculiarities. The focal mechanisms of the strongest shocks (M w > 5.0) were similar and involved thrust processes (Fig. 1); a migration of seismicity from east to west was observed. The seismic moment release was not characterized by a uniform temporal decay. Major aftershocks occurred on May 9, of M w 5.1, and on May 11, of M w 5.0, and then the seismicity decreased through to August. On September 11, two strong shocks occurred at 16:31 (M w 5.2) and 16:35 (M w 5.6), followed by two further strong events on September 15, at 03:15 (M w 5.9) and 09:21 (M w 6.0). The seismic activity then decreased until September 16 1977, when a M w 5.3 occurred. The last relevant event of the sequence occurred on 1979 April 18, with M w 4.8.The seismic moment release and its time evolution do not follow a simple occurrence model of mainshock-aftershock sequence, that is, a dominant large earthquake...

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Section: Seismotectonic Aspects Of the 1976—77 Friuli Seismic Sequencementioning

confidence: 91%

Section: Data Used For Modellingmentioning

confidence: 99%

Changes in failure stress and stress transfer during the 1976-77 Friuli earthquake sequence

Perniola

Bressan

Pondrelli

2004

Geophysical Journal International

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“…For contributing agencies to our earthquake catalog, see the section. Additionally, our earthquake catalog includes data from Schorn (1902), Förtsch and Schmedes (1976), Finetti et al (1979), Galadini and Galli (1999), Poli et al (2002), Ganas et al (2008), and Hammerl (2017). The catalog is available as supporting Data Set S2.…”

Section: The DI and Its Boundariesmentioning

confidence: 99%

Active Seismotectonic Deformation in Front of the Dolomites Indenter, Eastern Alps

et al. 2018

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We use earthquake focal mechanisms to study present‐day deformation and stress in the western part of the Eastern European Alps. We define the following regions, based on seismicity and kinematically compatible focal mechanism types: (1) the northern and western parts of the Dolomites indenter, the western and central Tauern Window, and the northern Alpine margin and foreland lack significant seismicity. (2) The indenter boundaries are characterized by strike‐slip faulting. Based on earthquake and geodetic data, the western and northern indenter boundaries are active sinistral and dextral strike‐slip/oblique slip faults. (3) West and north of the indenter corner, we observe normal and strike‐slip faulting in an up to 70 km‐wide zone. From west to east, the minimum horizontal stress rotates clockwise about 10–20°, from NE to ENE. (4) North of (3), east of the Swiss/Austrian border, we find evidence for N to NNW directed thrust faulting, and local orogen‐parallel extension. From our results and geodetic data, we infer that relative to a fixed northern foreland, NNW directed indentation is transferred at depth via the Sub‐Tauern thrust system to this 100‐km‐wide zone of localized thrusting. A lack of evidence for major, active strike‐slip faulting north of the Tauern Window is in line with geodetic data, which show no significant velocity difference between the northern part of the Eastern Alps and their foreland.

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“…2 [data from Gruppo di Lavoro CPTI (2008)]. An M W over 6 was reached in 5 cases only: among them, the 1976 event is the only one for which instrumental values were computed [local magnitude (M L ) 6.4 (Finetti et al, 1979), and M W 6.5 (http://www.globalcmt.org/CMTsearch.html)]. Some of these main quakes were recently associated to known faults by Galadini et al (2005) and Burrato et al (2008).…”

Section: Seismicity Of the Trieste Broader Regionmentioning

confidence: 99%

The contribution of “silent” faults to the seismic hazard of the northern Adriatic Sea

Slejko

Carulli

García

et al. 2011

Journal of Geodynamics

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The Friuli earthquake (1976–1977)

Cited by 22 publications

References 0 publications

Changes in failure stress and stress transfer during the 1976-77 Friuli earthquake sequence

Changes in failure stress and stress transfer during the 1976-77 Friuli earthquake sequence

Active Seismotectonic Deformation in Front of the Dolomites Indenter, Eastern Alps

The contribution of “silent” faults to the seismic hazard of the northern Adriatic Sea

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