The 1997 Umbria‐Marche, Italy, Earthquake Sequence: A first look at the main shocks and aftershocks

Amato, A.; Azzara, R. M.; Chiarabba, C.; Cimini, G. B.; Cocco, M.; Bona, M. Di; Margheriti, Lucia; Mazza, Salvatore; Mele, F.; Selvaggi, G.; Basili, A.; Boschi, E.; Courboulex, Françoise; Deschamps, A.; Gaffet, Stéphane; Bittarelli, G.; Chiaraluce, L.; Piccinini, D.; Ripepe, Maurizio

doi:10.1029/98gl51842

Cited by 296 publications

(189 citation statements)

References 5 publications

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“…During the sequence four additional events of 5.2 to 5.6 Mw occurred. All of the large shocks (Amato et al, 1998;Selvaggi et al, 2002;Chiaraluce et al, 2003) originated at 5 to 6 km depth and were on adjacent, parallel, northwest-trending normal faults. Figure 2 superimposes the position, focal mechanisms, and intensities of the main shocks on a structural sketch of the study area.…”

Section: Tectonic Settingmentioning

confidence: 99%

“…The southwest-dipping normal faults of the UFS are Quaternary age at the base of the basin's infill and are considered active from geomorphological (e.g., Ficcarelli and Mazza, 1990;Coltorti et al, 1998;Messina et al, 1999), geologic (e.g., Lavecchia et al, 1994;Calamita et al, 1999;Barchi et al, 2000;Mirabella and Pucci, 2002), and seismological evidence (e.g., Deschamps et al, 1984;Haessler et al, 1988;Amato et al, 1998;Ekström et al, 1998;Mariucci et al, 1999;Stramondo et al, 1999;Barba and Basili, 2000). Historical seismicity data (Imax = XMCS, CPTI, 1999) and recent earthquakes [Norcia, 1979, Ms (surface-wave magnitude) = 5.9; Gubbio, 1984, Ms = 5.2;Colfiorito, 1997Colfiorito, -1998, maximum Mw = 6.0] (Deschamps et al, 1984;Haessler et al, 1988;Deschamps et al, 2000) indicate an active stress field consistent with a geologic long-term stress field that has been active since the Quaternary (Mariucci et al, 1999).…”

Section: Tectonic Settingmentioning

confidence: 99%

“…These seismic lines cross a currently tectonically active area within the northern Apennines in central Italy (Colfiorito area). Between 1997 and 1998 this region underwent a long seismic crisis, characterized by six main shocks measuring 5.2 < Mw < 6.0, all nucleated on southwest-dipping normal faults (Amato et al, 1998;Selvaggi et al, 2002;Chiaraluce et al, 2003), where MW is the moment magnitude scale. The depths investigated by the seismic lines extend beyond 4 s two-way time (twt); traveltime roughly corresponds to about 10 km depth, which is comparable with the thickness of the shallow seismogenic layer (∼1-9 km below sea level; .…”

Section: Introductionmentioning

confidence: 99%

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Comparison between reprocessed seismic profiles: Seismologic and geologic data — A case study of the Colfiorito earthquake area

2006

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Seismic reflection data are used to reconstruct the subsurface geologic structures below the Umbria-Marche region in Italy, a highly seismogenic area with a recent history of seismic activity (the 1997-1998 Colfiorito sequence). We reprocess three vibroseis seismic profiles (acquired in the early 1980s for hydrocarbon exploration) whose stacked sections were optimized for relatively deep oil targets. On the reprocessed seismic profile closest to the epicentral area, we construct the main reflectors to a depth of about 4 s (two-way time) and compare this interpretation with the available hypocenters of the 1997 earthquakes.The improvements in visualizing the shallow and deep reflections provide a better correlation between the reflectors and the observed surface structures as well as a better delineation of the basement-rock geometry. We find that part of the Colfiorito sequence is localized around some of the reflectors in the reflection profile, which we interpret as related to the active normal faults that outcrop at the surface.

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Section: Tectonic Settingmentioning

confidence: 99%

Section: Tectonic Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison between reprocessed seismic profiles: Seismologic and geologic data — A case study of the Colfiorito earthquake area

2006

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“…Sites 1-11 (at three seismic stations) are in Umbria and Marche (Central Italy), in the area shaken by the 1997 Umbria-Marche Earthquake Sequence (Amato et al, 1998;Chiaraluce et al, 2003;Miller et al, 2004;Antonioli et al, 2005), as a result of an initiative of the Dipartimento Geotecnologie per l'Ambiente e il Territorio of Chieti-Pescara University. Most of the seismic sites (1-10) employ seismometers Willmore MARK III, with a minimum frequency sampling of 50 Hz.…”

Section: Data Collectionmentioning

confidence: 99%

Power-law frequency distribution of H/V spectral ratio of seismic signals: Evidence for a critical crust

Signanini

Santis

2012

Earth Planet Sp

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We analyse records from several seismic stations in Central Italy (including some with multiple recording sites) for the statistical properties of spectra of both noise and earthquake signals. The main result is that the power-law scaling of most of the spectral H/V ratio statistical distributions leads to a so-called heavy tail. This is interpreted as a statistical distribution with a fractal dimension of about 2, which is almost certainly caused by a porous percolating medium beneath the stations due to some universal property of the crustal rocks crossed by the elastic waves propagation suggesting that the uppermost crust is in a critical state.

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“…A long sequence of EQs, among them six with M between 5 and 6 that struck Central Italy from September and December 1997 is thoroughly examined by Amato et al (1998). The EQ series started of 3 September 1997 was followed by two strong shocks (M w 5.7 at 00:33 UT, and M L 6.4 at 09:40 UT followed by another secondary EQ shock of M L 5.3 at 09:47 UT) on 26 September (according to NEIC catalogue), and it continued with four stronger shocks (M w between 5.3 and 5.7) occurred on 3, 6, 12, and 14 October 1997.…”

Section: Earthquake Activity In Central Italy During September-octobementioning

confidence: 99%

Ionospheric transients observed at mid-latitudes prior to earthquake activity in Central Italy

Nenovski

Spassov

Pezzopane

et al. 2010

Nat. Hazards Earth Syst. Sci.

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Abstract.Ionograms from Rome (41.8N, 12.5E) and Sofia (42.4N, 23.2E) ionospheric stations during earthquake (EQ) activity with magnitude (M) between 5 and 6 in Central Italy are analyzed. It is found that several ionospheric disturbances occur in the intermediate E-F region before the EQ shock. In fact, besides sporadic E (Es) layer development (of type h) of short duration (transients), fmin increase, trace gaps near the critical frequencies, and E region trace disappearance are also observed within one to three hours before the EQ shock. Before the EQ shocks we find that the F2 region parameters are practically undisturbed. The only exception is the so-called fork trace that appears mostly near the critical frequency of the F2 region. Acoustic gravity waves (AGW) are suggested as one of the possible sources of transients observed in the ionosphere before the EQ shock.

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The 1997 Umbria‐Marche, Italy, Earthquake Sequence: A first look at the main shocks and aftershocks

Cited by 296 publications

References 5 publications

Comparison between reprocessed seismic profiles: Seismologic and geologic data — A case study of the Colfiorito earthquake area

Comparison between reprocessed seismic profiles: Seismologic and geologic data — A case study of the Colfiorito earthquake area

Power-law frequency distribution of H/V spectral ratio of seismic signals: Evidence for a critical crust

Ionospheric transients observed at mid-latitudes prior to earthquake activity in Central Italy

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