The 1997 Umbria‐Marche (Italy) earthquake sequence: Relationship between ground deformation and seismogenic structure

Cinti, F. R.; Cucci, Luigi; Marra, Francesco; Montone, P.

doi:10.1029/1999gl900142

Cited by 58 publications

(55 citation statements)

References 8 publications

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“…[73] measured few centimetres high strips of rejuvenation along the bedrock fault scarps and related these features to surface faulting; Cinti eta!. [74] interpreted the surface breaks as secondary ruptures along high-angle faults not directly related to the seismogenic source. A continuous surficial deformation has been derived from SAR interferometry and GPS which show the lowering of the Colfiorito basin due to the main shocks occurred on September 26 [75].…”

Section: Colfiorito Fault Systemmentioning

confidence: 99%

Plio-Quaternary changes of the normal fault architecture in the Central Apennines (Italy)

Galadini¹,

Messina²

2001

Geodinamica Acta

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The definition of the active fault geometry and kinematics in young evolving orogens may be difficult owing to changes in the structural architecture which may occur with a frequence of few hundred thousand years. Cases from the central Apennines well illustrate this problem. The Avezzano-Bussi and Vallelonga-Salto Valley fault systems (65 and 85 km long, respectively) show clear evidence of Pliocene-early Pleistocene activity and have been responsible for the formation of intermontane basins. Available geological data, however, indicate that only minor segments (the Tre Monti and Trasacco faults, both 7 km long) of the mentioned faults have to be considered active during the late Pleistocene-Holocene, as faults accommodating minor deformations inside an intermontane basin. The L' Aquila fault system underwent significant geometrical and kinematic modifications during the Quaternary, with the reactivation of minor portions of parallel normal faults to draw a new system of en-echelon normal-oblique left-lateral faults. The Laga Mts. fault experienced an along-fault activity migration. The portion of the fault which was active earlier during the Quaternary shows a significant decrease or end of the activity while a portion previously not active displays impressive evidence of late Pleistocene-Holocene displacements. Structural changes in the intermontane basins bounded by the Colfiorito fault system also indicate that the intensity of the tectonic activity decreased during the Quaternary. Not defining the structural evolution in the above mentioned cases would imply wrong conclusions for both the fault geometry and kinematics which may be delivered for seismotectonics and seismic hazard assessment. This typically leads to overestimate the fault length and the expected magnitude or to the increase in the number of seismogenic sources affecting an area. Finally, the definition of the structural evolution permits to select between different geometrical options in terms of active faulting framework (e.g. a system of parallel normal faults vs. a system of en-echelon normal oblique faults as in the case of the L' Aquila fault system) related to different geometries at depth (detachment normal fault vs. high-angle oblique fault). © 2001 Editions scientifiques et medicales Elsevier SAS active fault I structural evolution I fault kinematics 1 seismogenic structure I central Italy

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Section: Colfiorito Fault Systemmentioning

confidence: 99%

Plio-Quaternary changes of the normal fault architecture in the Central Apennines (Italy)

Galadini¹,

Messina²

2001

Geodinamica Acta

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“…The area is seismically active, and earthquakes with local magnitude ranging between M L 4.6 and M L 5.8 have occurred repeatedly . The last earthquake sequence in the area occurred between May 1997and April 1998(AMATO et al, 1998EKSTRÖ M et al 1998;CINTI et al, (Table 1). Moreover, due to the geological and climatic settings, landslides are abundant in Umbria and contribute to shape the landscape (GUZZETTI et al, 1996(GUZZETTI et al, , 2008.…”

Section: Study Areamentioning

confidence: 99%

Analysis of Ground Deformation Detected Using the SBAS-DInSAR Technique in Umbria, Central Italy

Guzzetti

Manunta

Ardizzone

et al. 2009

Pure appl. geophys.

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Ground deformation affecting the Umbria region (central Italy) in the 9-year period from 1992 to 2000 was investigated through multi-temporal Differential Synthetic Aperture Radar Interferometry (DInSAR). For the purpose, the Small BAseline Subset (SBAS) technique was adopted, which allows studying the temporal evolution of the detected deformation at two spatial scales: a low-resolution (regional) scale, and a full-resolution (local) scale. For the analysis, SAR data acquired by the European Remote Sensing (ERS-1/2) satellites along ascending and descending orbits were used. The detected deformation was analysed to investigate its relevance to geophysical, geomorphologic, and human-induced processes that may result in hazardous conditions to the population of Umbria. Low-resolution deformation data were used to: (i) determine the amount of displacement caused by the Umbria-Marche earthquake sequence from September 1997 to April 1998 in the Foligno area, (ii) determine the number and percentage of the known landslides that can be monitored by the DInSAR technology in the investigated area, and (iii) identify and measure subsidence induced by exploitation of a confined aquifer in the Valle Umbra. Results indicate that earthquakes moved through the Foligno area westwards up to 3.9 cm and with an uplift reaching 1.7 cm. Intersection in a GIS of the low-resolution deformation maps with a detailed landslide inventory map allowed the determination that the portion of landslides that can be monitored by the SBAS-DInSAR technique in Umbria ranges from 2.7% to 3.4%, and the percentage of the total landslide area ranges from 10.4% to 12.8%. In the Valle Umbra, a dependency was found between the time and the amount of detected ground deformation, and the record of water withdrawal. The full-resolution deformation data were used to investigate the movement of the Ivancich landslide, in the Assisi Municipality. Joint analysis of the spatial and the temporal characteristics of the ground displacement allowed the formulation of a hypothesis on the landslide geometry and deformation pattern. RI Guzzetti, Fausto/G-4404-201

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“…Although these shocks did not produce primary surface ruptures, the observed ground breaks (CINTI et al, 1999) identified a diffuse surface deformation along a 10-km-wide belt whose strike is in agreement with the The main shock occurred at 09:40 (M W ¼ 6.0; M 0 ¼ 1.26 · 10 25 dyne-cm) and accounts for about 50% of the total moment release in the sequence (EKSTRO¨M et al, 1998). The distribution of the moment release in several events of moderate size, instead of concentrating in a single large event, may be related to the structural complexity of the region.…”

Section: The 1997 Umbria-marche Italy Earthquake Sequencementioning

confidence: 99%

Preseismic Creep Strains Revealed by Ground Tilt Measurements in Central Italy on the Occasion of the 1997 Umbria-Marche Apennines Earthquake Sequence

Sgrigna¹,

Malvezzi²

2003

Pure and Applied Geophysics

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Daily averaged tilt component data from four sites of the Central Apennines (Italy) revealed intermediate-term tilts of a few months as possible precursors of the seismic sequence occurred in the Umbria-Marche region during 1997. A change was also observed in the secular tectonic trend recorded at one site and referred to the same seismic sequence. The observed intermediate-term preseismic tilts are considered as the manifestation of aseismic creep episodes in the fault materials close to the tilt sites. The mechanism refers to a strain field slowly propagating from the dilatancy (focal) area to the tiltmeters, through rigid crustal blocks separated by weak transition zones with viscoelastic rheology. This propagation is thought to be the cause of the local aseismic fault slip recorded by tiltmeters. In one case such creep strains revealed to have larger amplitude and higher frequency content than those accepted for fault materials, and this was attributed to an amplified response of the heterogeneous ground surface at the site. The existence of a propagating strain field is confirmed by the different onset time delays in the preseismic tilt signals recorded at different distances from the same earthquake. In particular, the onset time delays observed at each tilt site appear to increase with increasing distance of such site from the epicentral area. At greatest distances, where the preseismic strain becomes negligible, the characteristic intermediate-term ground tilts vanish completely.

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The 1997 Umbria‐Marche (Italy) earthquake sequence: Relationship between ground deformation and seismogenic structure

Cited by 58 publications

References 8 publications

Plio-Quaternary changes of the normal fault architecture in the Central Apennines (Italy)

Plio-Quaternary changes of the normal fault architecture in the Central Apennines (Italy)

Analysis of Ground Deformation Detected Using the SBAS-DInSAR Technique in Umbria, Central Italy

Preseismic Creep Strains Revealed by Ground Tilt Measurements in Central Italy on the Occasion of the 1997 Umbria-Marche Apennines Earthquake Sequence

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