Ground effects and surface faulting in the September–October 1997 Umbria–Marche (Central Italy) seismic sequence

Vittori, E.; Deiana, Giovanni; Esposito, E.; Ferreli, Luca; Marchegiani, L.; Mastrolorenzo, G.; Michetti, Alessandro Maria; Porfido, Sabina; Serva, Leonello; Simonelli, Armando Lucio; Tondi, Emanuele

doi:10.1016/s0264-3707(99)00056-3

Cited by 45 publications

(11 citation statements)

References 29 publications

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“…For the Colfiorito 1997 event, the interpretation of observed ground breaks as evidence of surface faulting is not unanimously accepted (e.g., Guerrieri et al, , and references therein). We follow the interpretation of Cello et al () and Vittori et al (), which pointed out surface faulting for the 26 September 1997 shock. InSAR data (Salvi et al, ; Stramondo et al, ) helped in constraining the position of the primary fault.…”

Section: Discussionsupporting

confidence: 86%

Characterizing the Distributed Faulting During the 30 October 2016, Central Italy Earthquake: A Reference for Fault Displacement Hazard Assessment

Ferrario

Livio

2018

Tectonics

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Moderate to strong earthquakes (i.e., Mw >~6.0) commonly produce a complex network of ground ruptures, which are responsible for significant damage. Distributed faulting can affect wide areas (tenths of square kilometers), and expected displacement can be estimated through a probabilistic approach, considering distance from the primary fault and earthquake magnitude. Other factors may have a role in driving the occurrence of distributed faulting; nevertheless, they are not adequately addressed in the current modeling, due to a sensible lack of information. We study the 30 October 2016, Central Italy earthquake (Mw 6.5), to analyze the spatial pattern and geometric characteristics of distributed faulting. We found that distance from the primary structure, fault geometry, and lithology are key factors controlling the distributed faulting occurrence; the local structural setting (i.e., synthetic versus antithetic normal faults systems and relay zones) drives the spatial distribution of faults and the partitioning of the deformation. We also examine other four events occurred in the Italian Apennines since 1980, confirming that traditional models can underestimate the probability of distributed faulting. We suggest that a purely distance-based probabilistic approach should be integrated using additional parameters derived from earthquake deformation fields or considering the reactivation of preexisting faults.Plain Language Summary Surface faulting caused by moderate to strong earthquakes may occur along the major fault plane (primary fault) or along other structures in its proximity (distributed faulting). Distributed faulting can affect wide areas (tenths of square kilometers) and is responsible for significant damage. We assess the spatial pattern and geometric characteristics of distributed faulting of the 30 October 2016 Central Italy earthquake. We found that distance from the primary structure, fault geometry, and lithology are key factors controlling the distributed faulting occurrence. We also analyze four events that hit the Italian Apennines since 1980 and compare the results with the models currently adopted for estimating the possible amount of surface faulting caused by earthquakes. We found that current models, which are based on traditional field mapping methods, underestimate the probability of distributed faulting. We argue that the Central Italy 2016 event can act as a reference case study for fault displacement hazard assessment and that an increasing number of case histories will improve future mitigation strategies.PFDHA is the suggested approach for locating and designing critical or distributive infrastructures and utility lines, such as nuclear power plants (ANSI/ANS-2.30, 2015) and water pipelines. This method computes the probability of faulting occurrence as a function of distance from the primary fault and of earthquake FERRARIO AND LIVIO 1256

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Section: Discussionsupporting

confidence: 86%

Characterizing the Distributed Faulting During the 30 October 2016, Central Italy Earthquake: A Reference for Fault Displacement Hazard Assessment

Ferrario

Livio

2018

Tectonics

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“…The clays within the PSZs likely act as seals and promote the generation of high fluid pressures along faults [ Blanpied et al ., ]. The evident interaction of fluids with clay‐bearing carbonate fault gouges may be a contributing factor toward the common occurrence of surface‐breaking scarps in the Northern Apennines [e.g., Vittori et al ., ; Guerrieri et al ., ].…”

Section: Discussionmentioning

confidence: 99%

An experimental investigation into the role of phyllosilicate content on earthquake propagation during seismic slip in carbonate faults

2015

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Carbonate faults commonly contain small amounts of phyllosilicate in their slip zones, due to pressure solution and/or clay smear. To assess the effect of phyllosilicate content on earthquake propagation in carbonate faults, friction experiments were performed at 1.3 m/s on end‐members and mixtures of calcite, illite‐smectite, and smectite gouge. Experiments were performed at 9 MPa normal load, under room humidity and water‐saturated conditions. All dry gouges show initial friction values (μi) of 0.51–0.58, followed by slip hardening to peak values of 0.61–0.76. Slip weakening then ensues, with friction decreasing to steady state values (μss) of 0.19–0.33 within 0.17–0.58 m of slip. Contrastingly, wet gouges containing 10–50 wt % phyllosilicate exhibit μi values between 0.07 and 0.52 followed by negligible or no slip hardening; rather, steady state sliding (μss ≪ 0.2) is attained almost immediately. Microstructurally, dry gouges show intense cataclasis and wear within localized principal slip zones, plus evidence for thermal decomposition of calcite. Wet gouges exhibit distributed deformation, less intense cataclasis, and no evidence of thermal decomposition. It is proposed that in wet gouges, slip is distributed across a network of weak phyllosilicate formed during axial loading compaction prior to shear. This explains the (1) subdued cataclasis and associated lack of slip hardening, (2) distributed nature of deformation, and (3) lack of evidence for thermal decomposition, due to low friction and lack of slip localization. These findings imply that just 10% phyllosilicate in the slip zone of fluid‐saturated carbonate faults can (1) dramatically change their frictional behavior, facilitating rupture propagation to the surface, and (2) significantly lower frictional heating, preventing development of microscale seismic markers.

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“…The scenario of surface ruptures triggered by the 2009 L'Aquila earthquake is typical for moderate (6.0 < M < 6.5) earthquakes in the Apennines, as clearly observed during similar events in the past 15 years [ Vittori et al , 2000; Michetti et al , 2000]. Field observations documented unequivocally the pattern of surface faulting along the Paganica Fault, characterized by tectonic ruptures aligned for almost 3 km and vertical offsets frequently higher than 7–8 cm which increased to more than 10 cm in the postseismic phase [ Wilkinson et al , 2010].…”

Section: Discussionmentioning

confidence: 99%

“…While most of the published models agree with the general pattern of deformation, they provided ambiguous results regarding the upward extension of the surface slip along the fault. This is typical for moderate earthquakes ( M w around 6) particularly when surface deformation and displacements are too small for unequivocal source parameter inversion [e.g., Vittori et al , 2000; Salvi et al , 2000; Biggs et al , 2006].…”

Section: Introductionmentioning

confidence: 99%

InSAR data as a field guide for mapping minor earthquake surface ruptures: Ground displacements along the Paganica Fault during the 6 April 2009 L'Aquila earthquake

Guerrieri¹,

Baer²,

Hamiel³

et al. 2010

J. Geophys. Res.

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, a moderate earthquake (M w = 6.3; M l = 5.8) struck the Abruzzo region in central Italy, causing more than 300 fatalities and heavy damage to L'Aquila and surrounding villages. Coseismic surface effects have been thoroughly documented by timely field surveys as well as by remote sensing analyses of satellite images. The outstanding quality of geological, seismological, geodetic, and interferometric synthetic aperture radar (InSAR) information arguably represents the best ever data set made available immediately after a moderate seismic event. Based on this data set, we aim at testing the capability of coupled geological and InSAR data to map surface faulting patterns associated with moderate earthquakes. Coseismic ground ruptures have been mapped at a scale of 1:500 in the whole epicentral area. Traces of surface ruptures have been inferred from linear phase discontinuities identified in the interferogram. A very good agreement between the two methods resulted in the characterization of the main surface rupture along the Paganica fault. The same approach applied to ground ruptures hypothesized along other capable fault segments provided more questionable results. Thus, the combined field and InSAR approach appeared useful for detecting continuous surface ruptures exceeding 1 km in length and showing displacements greater than a few centimeters. These are the typical faulting parameters for moderate earthquakes (6.0 < M w < 6.5) in central Apennines. For continuous ground cracks shorter than a few hundred meters and/or that show displacements smaller than 1-2 cm, the described approach may be less helpful, most probably due to the limited resolution of the data.Citation: Guerrieri, L., et al. (2010), InSAR data as a field guide for mapping minor earthquake surface ruptures: Ground displacements along the Paganica Fault during the 6

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Ground effects and surface faulting in the September–October 1997 Umbria–Marche (Central Italy) seismic sequence

Cited by 45 publications

References 29 publications

Characterizing the Distributed Faulting During the 30 October 2016, Central Italy Earthquake: A Reference for Fault Displacement Hazard Assessment

Characterizing the Distributed Faulting During the 30 October 2016, Central Italy Earthquake: A Reference for Fault Displacement Hazard Assessment

An experimental investigation into the role of phyllosilicate content on earthquake propagation during seismic slip in carbonate faults

InSAR data as a field guide for mapping minor earthquake surface ruptures: Ground displacements along the Paganica Fault during the 6 April 2009 L'Aquila earthquake

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