Accelerometric radiation simulation for the September 26, 1997 Umbria-Marche (Central Italy) main shocks

Numerous existing steel framed buildings located in earthquake prone regions world-wide were designed without seismic provisions. Slender beam-columns, as well as non-ductile beam-to-column connections have been employed for multi-storey moment-resisting frames (MRFs) built before the 80’s. Thus, widespread damage due to brittle failure has been commonly observed in the past earthquakes for steel MRFs. A recent post-earthquake survey carried out in the aftermath of the 2016-2017 Central Italy seismic swarm has pointed out that steel structures may survive the shaking caused by several main-shocks and strong aftershocks without collapsing. Inevitably, significant lateral deformations are experienced, and, in turn, non-structural components are severely damaged thus inhibiting the use of the steel building structures. The present papers illustrates the outcomes of a recent preliminary numerical study carried out for the case of a steel MRF building located in Amatrice, Central Italy, which experienced a series of ground motion excitations suffering significant damage to the masonry infills without collapsing. A refined numerical model of the sample structure has been developed on the basis of the data collected on site. Given the lack of design drawings, the structure has been re-designed in compliance with the Italian regulations imposed at the time of construction employing the allowable stress method. The earthquake performance of the case study MRF has been then investigated through advanced nonlinear dynamic analyses and its structural performance has been evaluated according to Eurocode 8-Part 3 for existing buildings. The reliability of the codified approaches has been evaluated and possible improvements emphasized.

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Spatio-temporal variation of Anaelastic and Scattering Seismic Attenuation during the 2016-2017 Central Italy Seismic Sequence

10.5194/egusphere-egu21-8802 ◽

2021 ◽

Author(s):

Simona Gabrielli ◽

Aybige Akinci ◽

Ferdinando Napolitano ◽

Luca De Siena ◽

Edoardo Del Pezzo ◽

...

Keyword(s):

Wave Attenuation ◽

Central Italy ◽

Temporal Variations ◽

Seismic Attenuation ◽

Coda Wave ◽

Seismic Sequence ◽

Rock Fracturing ◽

Low Frequencies ◽

Main Shocks ◽

Stress Changes

Between August and October 2016, the Central Apennines in Italy have been struck by a long-lasting seismic sequence, known as the Amatrice (Mw 6.0) - Visso (Mw 5.9) - Norcia (Mw 6.5) sequence. The cascading ruptures occurred in this sequence have been considered connected to the fluid migration in the fault network, as suggested by previous studies. The behaviour of fluids in the crust is crucial to understand earthquakes occurrence and stress changes since fluids reduce fault stability. It has long been understood that the seismic attenuation is strongly controlled by the structural irregularity and heterogeneities; micro-cracks and cavities, either fluid-filled or dry, temperature and pressure variations cause a decrease in seismic wave amplitude and pulse broadening. Hence seismic attenuation imagining is a powerful tool to be a relevant provenance of information about the influence and abundance of fluids in a seismic sequence.The aim of this work is to separate scattering and absorption contributions to the total attenuation of coda waves and to provide their spatial and temporal variations at different frequency bands of these quantities using two datasets: the first one comprising 592 earthquakes occurred before the sequence (March 2013-August 2016) and the second one comprising 763 events (ML > 2.8) from the Amatrice-Visso-Norcia sequence. Scattering and absorption have been measured through peak-delay and coda-wave attenuation parameters (the latter inverted using frequency-dependent sensitivity kernels).The preliminary results show a clear difference between the pre-sequence and sequence images, mainly at low frequencies (1.5 Hz), where we can define a spatial increase of scattering with time attributed to rock fracturing and fluid circulation. The coda attenuation tomography also demonstrates a clear variation between the pre-sequence and the sequence over series of time windows being before and after the largest main shocks of the seismic sequence, with an increase of the attenuation in space with decreasing time. The peak delay indicates a high scattering area corresponding to the Gran Sasso massif and L&#8217;Aquila zone, where an important seismic sequence (Mw 6.3) occurred in 2009.

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Analysis of a database of landslides triggered by the 2016 Central Italy seismic sequence

10.5194/egusphere-egu21-1597 ◽

2021 ◽

Author(s):

Giovanni Forte ◽

Melania De Falco ◽

Federica Iannicelli ◽

Antonio Santo

Keyword(s):

Central Italy ◽

Google Earth ◽

Mountain Range ◽

Seismic Sequence ◽

Large Area ◽

Geometrical Characterization ◽

Seismic Parameters ◽

Main Shocks ◽

Ground Effects ◽

Transportation Routes

The seismic sequence that struck Central Italy in 2016 was characterized by three main shocks respectively occurred on August 24th Mw 6.0; October 26th Mw5.9 and October 30th Mw 6.5. The seismic sequence caused several ground effects over a large area of &#8203;&#8203;the central Apennine mountain range, mainly affecting transportation routes.In the aftermath of the sequence, several research groups mapped around 820 landslides involving road cuts in rock and fill slopes over an area of about 2000 km2 (GEER,ISPRA, C.E.R.I. by Roma La Sapienza). These data are summarized in the CEDIT catalog by Martino et al., (2017), where almost 150, 250 and 420 instability phenomena were respectively triggered by each mainshock. Further updates were carried out by the Authors in the framework of the Reluis projects of the Department of Civil Protection. In particular, other 550 phenomena were mapped by interpretation of aero photos provided by google-earth. For some of the largest ones, field surveys were carried out for mechanical, structural, and geometrical characterization.The dataset distribution was analyzed with geological, geomorphological, and seismic parameters, such as lithology, fault distance, landslide run-out, estimates of mobilized volumes, distance from the epicenter, PGA, and damages.The triggered events are mainly characterized by Category I of Keefer (1984) classification, namely rockfalls and rockslides. The maximum triggering distance resulted as high as 50 km far from the epicenter. The most affected areas are characterized by ridge crests or flanks of valleys in carbonate rocks.This study permitted to highlight the most relevant parameters for the assessment of earthquake-triggered susceptibility for the study area and identify some meaningful and critical case studies for the future development of the research.&#160;

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Active Faulting in Source Region of 2016–2017 Central Italy Event Sequence

Earthquake Spectra ◽

10.1193/101317eqs204m ◽

2018 ◽

Vol 34 (4) ◽

pp. 1557-1583 ◽

Cited By ~ 11

Author(s):

Fabrizio Galadini ◽

Emanuela Falcucci ◽

Stefano Gori ◽

Paolo Zimmaro ◽

Daniele Cheloni ◽

...

Keyword(s):

Source Region ◽

Central Italy ◽

Active Faults ◽

Earthquake Sequence ◽

Fault System ◽

Fault Plane Solutions ◽

Moment Tensors ◽

Central Italy Earthquake ◽

Finite Fault ◽

Main Shocks

The Central Italy earthquake sequence produced three main shocks: M6.1 24 August, M5.9 26 October, and M6.5 30 October 2016. Additional M5–5.5 events struck this territory on 18 January 2017 in the Campotosto area. Fault plane solutions for the main shocks exhibit normal faulting (characteristic of crustal extension occurring in the inner central Apennines). Significant evidence, including hypocenter locations, strike and dip angles of the moment tensors, inverted finite fault models (using GPS, interferometric aperture radar, and ground motion data), and surface rupture patterns, all point to the earthquakes having been generated on the Mt. Vettore–Mt. Bove fault system (all three main shocks) and on the Amatrice fault, in the northern sector of the Laga Mountains (portion of 24 August event). The earthquake sequence provides examples of both synthetic and antithetic ruptures on a single fault system (30 October event) and rupture between two faults (24 August event). We describe active faults in the region and their segmentation and present understanding of the potential for linkages between segments (or faults) in the generation of large earthquakes.

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Rupture history of the 1997 Umbria-Marche (Central Italy) main shocks from the inversion of GPS, DInSAR and near field strong motion data

Annals of Geophysics ◽

10.4401/ag-3349 ◽

2009 ◽

Vol 47 (4) ◽

Author(s):

B. Hernandez ◽

M. Cocco ◽

F. Cotton ◽

S. Stramondo ◽

O. Scotti ◽

...

Keyword(s):

Near Field ◽

Central Italy ◽

Strong Motion ◽

Strong Motion Data ◽

Motion Data ◽

Main Shocks ◽

History Of

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Fault Segmentation as Constraint to the Occurrence of the Main Shocks of the 2016 Central Italy Seismic Sequence

Tectonics ◽

10.1002/2017tc004652 ◽

2017 ◽

Vol 36 (11) ◽

pp. 2370-2387 ◽

Cited By ~ 65

Author(s):

A. Pizzi ◽

A. Di Domenica ◽

F. Gallovič ◽

L. Luzi ◽

R. Puglia

Keyword(s):

Central Italy ◽

Seismic Sequence ◽

Fault Segmentation ◽

Main Shocks

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In search of evidence of deep fluid discharges and pore pressure evolution in the crust to explain the seismicity style of the Umbria-Marche 1997-1998 seismic sequence (Central Italy)

Annals of Geophysics ◽

10.4401/ag-3743 ◽

1999 ◽

Vol 42 (4) ◽

Author(s):

F. Quattrocchi

Keyword(s):

Pore Pressure ◽

Frictional Heating ◽

Central Italy ◽

Frictional Stress ◽

Seismic Sequence ◽

Fluid Geochemistry ◽

Main Shocks ◽

Dehydration Reactions ◽

Frictional Instability ◽

Seismogenic Process

Starting soon after the first main-shocks of the long seismic sequence which has occurred along the Umbria-Marche boundary since September 1997, fluid geochemistry surveying was accomplished (around 200 samples) over the epicentre area as a whole, collecting information on hydrological variations too. The collected experimental data allowed to discuss the spatial and temporal evolution of the circulating fluids, either in the chemistry or in the dynamic paths, during the different stages of the seismic sequence. All the geo-structural, seismological and fluid geochemistry information gathered in this sector of the Central Apennines are discussed together in an attempt to speculate about the possible role and evolution of pore-pressure at depth up to surface within the seismogenic process recalling the "Fault Valve Activity Model", the "Coseismic Strain Model", the "frictional heating-frictional stress coupling model" and the "Dilatancy Model". This overview may also explain the geochemical and hydrological experimentally observed anomalies, in occurrence of the seismic sequence. The seismic style of the long sequence is revised in terms of pore-pressure regime down to seismogenic depth (2-10 km), within the poly-phase Evaporite Triassic Basement (ETB) and the Paleozoic Crystalline Basement (PCB), corresponding to the horizons of transient dehydration reactions: process triggered and enhanced during the seismogenic process, involving further fluid overpressure, and consequently further seismicity (chain effect). All the recalled processes and models may explain fluid remobilization and over-pressuring in the upper crust starting soon after the main-shocks, along relict low angle planes (close Apennine and anti-Apennine fault segments), rendering the Umbria-Marche boundary a "transiently weakened frictional instability zone", for a period spanning more than one year.

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Heterogeneous Behavior of the Campotosto Normal Fault (Central Italy) Imaged by InSAR GPS and Strong-Motion Data: Insights from the 18 January 2017 Events

Remote Sensing ◽

10.3390/rs11121482 ◽

2019 ◽

Vol 11 (12) ◽

pp. 1482 ◽

Cited By ~ 5

Author(s):

Daniele Cheloni ◽

Nicola D’Agostino ◽

Laura Scognamiglio ◽

Elisa Tinti ◽

Christian Bignami ◽

...

Keyword(s):

Central Italy ◽

Sampling Rate ◽

Strong Motion ◽

Normal Fault ◽

Slip Distribution ◽

Fault System ◽

Time Interval ◽

Seismic Sequence ◽

Main Shocks ◽

Heterogeneous Behavior

On 18 January 2017, the 2016–2017 central Italy seismic sequence reached the Campotosto area with four events with magnitude larger than 5 in three hours (major event MW 5.5). To study the slip behavior on the causative fault/faults we followed two different methodologies: (1) we use Interferometric Synthetic Aperture Radar (InSAR) interferograms (Sentinel-1 satellites) and Global Positioning System (GPS) coseismic displacements to constrain the fault geometry and the cumulative slip distribution; (2) we invert near-source strong-motion, high-sampling-rate GPS waveforms, and high-rate GPS-derived static offsets to retrieve the rupture history of the two largest events. The geodetic inversion shows that the earthquake sequence occurred along the southern segment of the SW-dipping Mts. Laga normal fault system with an average slip of about 40 cm and an estimated cumulative geodetic moment of 9.29 × 1017 Nm (equivalent to a MW~6). This latter estimate is larger than the cumulative seismic moment of all the events, with MW > 4 which occurred in the corresponding time interval, suggesting that a fraction (~35%) of the overall deformation imaged by InSAR and GPS may have been released aseismically. Geodetic and seismological data agree with the geological information pointing out the Campotosto fault segment as the causative structure of the main shocks. The position of the hypocenters supports the evidence of an up-dip and northwestward rupture directivity during the major shocks of the sequence for both static and kinematic inferred slip models. The activated two main slip patches are characterized by rise time and peak slip velocity in the ranges 0.7–1.1 s and 2.3–3.2 km/s, respectively, and by ~35–50 cm of slip mainly concentrated in the shallower northern part of causative fault. Our results show that shallow slip (depth < 5 km) is required by the geodetic and seismological observations and that the inferred slip distribution is complementary with respect to the previous April 2009 seismic sequence affecting the southern half of the Campotosto fault. The recent moderate strain-release episodes (multiple M~5–5.5 earthquakes) and the paleoseismological evidence of surface-rupturing events (M~6.5) suggests therefore a heterogeneous behavior of the Campotosto fault.

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Spatio-temporal seismic velocity variations associated to the 2016–2017 central Italy seismic sequence from noise cross-correlation

Geophysical Journal International ◽

10.1093/gji/ggz429 ◽

2019 ◽

Vol 219 (3) ◽

pp. 2165-2173

Author(s):

Gaia Soldati ◽

Lucia Zaccarelli ◽

Licia Faenza

Keyword(s):

Seismic Waves ◽

Seismic Velocity ◽

Linear Trend ◽

Central Italy ◽

Fault System ◽

Seismic Sequence ◽

Sedimentary Deposits ◽

Main Shocks ◽

Spatio Temporal ◽

Velocity Changes

SUMMARY We investigate the temporal changes of crustal velocity associated to the seismic sequence of 2016–2017, which struck central Italy with a series of moderate to large earthquakes. We cross-correlate continuous recordings of 2 yr of ambient seismic noise from a network of 28 stations within a radius of 90 km around Amatrice town. We then map the spatio-temporal evolution of the velocity perturbations under the effect of subsequent earthquakes. Coinciding with each of the three main shocks of the sequence we observe a sudden drop of seismic velocity which tends to quickly recover in the short term. After the end of the strongest activity of the sequence, the coseismic velocity changes display gradual healing towards pre-earthquake conditions following a quasi-linear trend, such that by the end of 2017 about 75 per cent of the perturbation is recovered. The spatial distribution of the velocity drop fluctuates with time, and the area that shows the most intense variations beyond the ruptured fault system elongates in the NE direction. This zone roughly corresponds to a region of foredeep sedimentary deposits consisting of highly hydrated and porous sandstones, which respond to the passage of seismic waves with increased pore pressure and crack number, leading to a reduction of the effective relative velocity.

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Development of parametric seismic fragility curves for historical churches

Bulletin of Earthquake Engineering ◽

10.1007/s10518-021-01174-1 ◽

2021 ◽

Author(s):

Alessandra Marotta ◽

Domenico Liberatore ◽

Luigi Sorrentino

Keyword(s):

Seismic Performance ◽

Structural Damage ◽

Seismic Vulnerability ◽

Failure Modes ◽

Fragility Curves ◽

Central Italy ◽

Ratio Test ◽

Main Shocks ◽

Structural Details ◽

Masonry Churches

AbstractFor both spiritual and cultural reasons, churches are an essential part of the historical heritage of several countries worldwide, including Europe, Americas and Australasia. The extreme damage that occurred during the 2016–2017 Central Italy seismic swarm highlighted once again the noteworthy seismic vulnerability of unreinforced masonry churches, which exhibited several collapses and caused uncountable losses to the Italian artistic heritage. The seismic performance of 158 affected buildings was analyzed in the aftermath of the main shocks. The failure modes activated by the earthquakes were identified making reference to the local mechanisms currently considered in Italy for post-seismic assessment of churches. The structural damage of the investigated buildings, related to 21 mechanisms rather than to an overall global response, was explained resorting to empirical statistical procedures taking into account ground motion intensity and structural details that can worsen or improve the seismic performance. Finally, parametric fragility curves were derived selecting those structural details that mostly influence the damage by means of the likelihood-ratio test. Developed models can be used in future territorial-scale scenario or risk analyses.

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