seismic response of a deep continental basin including velocity inversion the sulmona intramontane basin central apennines italy

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Multiple Lines of Evidence for a Potentially Seismogenic Fault Along the Central-Apennine (Italy) Active Extensional Belt–An Unexpected Outcome of the MW6.5 Norcia 2016 Earthquake

The Apenninic chain, in central Italy, has been recently struck by the Norcia 2016 seismic sequence. Three mainshocks, in 2016, occurred on August 24 (MW6.0), October 26 (MW 5.9) and October 30 (MW6.5) along well-known late Quaternary active WSW-dipping normal faults. Coseismic fractures and hypocentral seismicity distribution are mostly associated with failure along the Mt Vettore-Mt Bove (VBF) fault. Nevertheless, following the October 26 shock, the aftershock spatial distribution suggests the activation of a source not previously mapped beyond the northern tip of the VBF system. In this area, a remarkable seismicity rate was observed also during 2017 and 2018, the most energetic event being the April 10, 2018 (MW4.6) normal fault earthquake. In this paper, we advance the hypothesis that the Norcia seismic sequence activated a previously unknown seismogenic source. We constrain its geometry and seismogenic behavior by exploiting: 1) morphometric analysis of high-resolution topographic data; 2) field geologic- and morphotectonic evidence within the context of long-term deformation constraints; 3) 3D seismological validation of fault activity, and 4) Coulomb stress transfer modeling. Our results support the existence of distributed and subtle deformation along normal fault segments related to an immature structure, the Pievebovigliana fault (PBF). The fault strikes in NNW-SSE direction, dips to SW and is in right-lateral en echelon setting with the VBF system. Its activation has been highlighted by most of the seismicity observed in the sector. The geometry and location are compatible with volumes of enhanced stress identified by Coulomb stress-transfer computations. Its reconstructed length (at least 13 km) is compatible with the occurrence of MW≥6.0 earthquakes in a sector heretofore characterized by low seismic activity. The evidence for PBF is a new observation associated with the Norcia 2016 seismic sequence and is consistent with the overall tectonic setting of the area. Its existence implies a northward extent of the intra-Apennine extensional domain and should be considered to address seismic hazard assessments in central Italy

Newly identified active faults in the Pollino seismic gap, southern Italy, and their seismotectonic significance

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Regional and site-specific GMPEs for Italian territory

The increasing number of records in the last years allows us a detailed statistical analysis of the strong motion data. In this study we would like to present a Regional and site-specific approach thanks to a huge and high quality accelerometric dataset for all the Italian territory of more of 120000 waveforms up to 150 km for more than 2300 events occurred in a time-span 2009-2017. This huge dataset allows us to regionalize the GMPEs, dividing the Italian territory in three parts, estimating for each part a different GMPE, for an expanded range of ground motion parameters such as: peak ground parameters (displacement, velocity and acceleration), the pseudo spectral accelerations at different periods (0.3, 1.0 and 3.0 seconds) and Arias and Housner intensities. In particular we study the 2016-2017 Central Italy sequence, in which many records for single stations are collected and site-specific GMPEs estimated. The resultant GMPEs are tested using an independent testing database and used as setup of the configuration of a near real-time ShakeMap system

Testing the seismogenic sources of the January 11th 1693 Sicilian earthquake (Io X/XI): insights from macroseismic field simulations

In January 11th 1693 an earthquake, commonly reported as the largest Italian seismic event (Io = X/XI MCS and Mw 7.4 according to CPTI04 reference catalogue), occurred in eastern Sicily, causing more than 54.000 casualties and totally destruction in the areas embracing the nowadays provinces of Catania, Siracusa and Ragusa. The entire Sicily Ionian coast was hit by a tsunami, with waves up to 8 metres high. Several geological sources differing in location, attitude and kinematics have been proposed by different authors for this earthquake: the NNW-SSE Malta Escarpment normal fault located offshore the eastern coast of Sicily, the nearly N-S Scicli strike-slip fault located in the central Hyblean plateau, the WSW-ENE Scordia-Lentini graben in the northern Hyblean region, the NW-dipping Ionian subduction plane, and lastly the NNW-dipping Sicilian Basal Thrust across the central-eastern Sicily and the Ionian offshore. In this paper, we attempt to discriminate among the above sources by applying a forward modelling technique which, starting from given fault model parameters (strike, dip, length, width, hypocentral location and magnitude) and reproducing acceleration time history above 1 Hz (the range of frequencies correlated with building damage), calculates the data point intensities at the surface. The differences between the observed and calculated macroseismic intensities, expressed as L1 norm, are discussed in order to identify the better analytical solutions. The obtained results are strongly dependent from the equivalent magnitude (Mw) attributed to the 1693 event, which in the literature ranges from Mw 6.8 to 8.0. Almost all the analysed fault models fall to reproduce the highest intensity (X/XI MCS) data points of the Hyblean region, suggesting that this area might have undergone a cumulative damage effects due to an intense foreshock activity (January 9th 1693, Mw 6.2, and January 11th 1693, morning, Mw 4.3). The portion of the macroseismic field located north of the Gela-Catania thrust front is better reproduced by the Malta Escarpment solution (Mw 7.1) and subordinately by the Sicilian Basal Thrust and by the Scordia-Lentini graben source models. The Hyblean portion of the field is better reproduced by the Ionian Subduction Plane (Mw 8) and subordinately by the Scicli line (Mw 7.4 and 7.1) source models. The entire field is better reproduced by the Scicli line related sources (Mw 7.1 and 7.4). Regional scale geological and seismotectonic considerations may help to further discriminate among the various sources

The May-June 2012 Ferrara Arc earthquakes (northern Italy): structural control of the spatial evolution of the seismic sequence and of the surface pattern of coseismic fractures

The Ferrara 2012 seismic sequence was characterized by two main compressional events, which occurred on May 20 and 29, 2012, with Mw 6.1 and Mw 6.0, respectively (quick Regional Centroid Moment Tensor [RCMT] at http://autorcmt.bo.ingv.it/quicks.html). These events were followed by five events with Mw >5.0 (two on May 20 and three on May 29, 2012) and by hundreds of events of lower magnitudes distributed along a WNW-ESE-elongated area of ca. 500 km2 (ISIDe database at http://iside.rm.ingv.it/ iside/standard/index.jsp.). The ongoing activity of the northward-verging fold-and-thrust structures of the Ferrara-Romagna Arc (Figure 1A) and the eastward-verging Coastal Adriatic Arc (referred to as the Outer Thrust System [OTS] in Lavecchia et al. 2003) has been a debated topic in the Italian literature. […

Segmentation pattern and structural complexities in seismogenic extensional settings: The North Matese Fault System (Central Italy)

We investigated the northern slope of the Matese Mts. (Molise, Central Italy) with the aim of characterizing the N- to NE-dipping active normal fault system in the Bojano basin, a sector of primary importance from a seismic hazard perspective. We collected field data to define the geometry and segmentation pattern of two sub-systems (Patalecchia-Colle di Mezzo and Bojano–Campochiaro). New evidence of late Quaternary faulting was obtained by exploiting well log interpretations. Kinematic analysis revealed the interaction of pre-Quaternary inherited (mainly E-W-striking) and newly formed (NW-SE-striking) normal faults. Slip accommodation through linkage was clearly noted in the case of the Patalecchia-Colle di Mezzo sub-system. Detailed topographic profiles across the active fault segments provided post-LGM (15 ± 3 kyr) slip rates up to ∼2 mm/yr which agree with the high deformation rates based on different approaches in the literature. Finally, the instrumental seismicity analysis constrained the bottom of the seismogenic layer to depths of 13–14 km, and the gathered information allowed us to reconstruct the North Matese seismogenic source. Its 3D geometry and dimensions agree with both the dimension-magnitude relationships and macroseismic information available for the 1805 earthquake (Mw 6.6), the main historical earthquake to have struck the Bojano basin

Multidisciplinary inferences on a newly recognized active east-dipping extensional system in Central Italy

AbstractWe use a multidisciplinary approach to gather preliminary evidence for a Quaternary east‐dipping extensional detachment in Central Italy. This structure crops out in the Sabini‐Eastern Simbruini (SES) and would be hidden at mid‐crustal depths beneath the L'Aquila 2009 (Mw6.3) epicentral area. The SES geometry is reconstructed through geological mapping, structural analysis and seismic line interpretation. The geometry of the mid‐crustal segment, referred to as the Ocre Segment (OS), is interpreted through seismological analyses of the largest aftershock (Mw5.4) of the L'Aquila 2009 sequence. The kinematic compatibility between the SES and the OS under a common SW–NE tensional field is tested through stress inversion of both geological and seismological data. The reliability of OS activation is tested through slip tendency analysis. Like other Italian cases, the SES and the OS are preliminarily interpreted as expressions at different depths of the same unknown east‐dipping extensional detachment, characterized by a ramp–flat–ramp geometry

QUaternary fault strain INdicators database: QUIN 1.0 - first release from the Apennines of central Italy

This database relates to the paper “QUaternary fault strain INdicators database - QUIN 1.0 - first release from the Apennines of central Italy”. It provides very local-scale geometric and kinematic data on Fault Striation Pairs (FSP, the fault plane and the slickenline measured on it) surveyed along the Quaternary (last 2.5 My) extensional intra-Apennine belt of central Italy. The sampled area develops for an along-strike extent of ~550 km and in an average NW-SE direction. The first release of the “QUaternary fault strain INdicator” database (acronym QUIN) consists of a comprehensive compilation of both unpublished (1315) and published (2026) FSPs, for a total of 3339 records. Overall, considering the ~60,100 numerical data released in this database, the 79.8% are unpublished while the 20.2% are from the previous literature. The FSP data are distributed within ~455 Survey Sites (SS) geolocated along the trace of well-distinct hosting faults. The database is released in a .txt table and as shapefile (.shp) in WGS84 coordinate system. The FSP records are organized in 34 fields, referring to three themes: A) FSP identification and SS location (fields 1 to 12); B) FSP geometry with quality ranking and references (fields 13 to 22); C) FSP deformation axes (fields 23 to 34). The first two domains include for each FSP the geographic and structural position, the SS name, the hosting fault-system name and average dip-direction, the geometric parameters (strike, dip-direction and dip, and trend and plunge), the newly calculated rake and corresponding kinematic classifications, the references of the field data and two quality rankings on the input data resolutions and location. The third domain, entirely new from this work, includes for each FSP, the attitude ( trend and plunge) of the kinematic axes (P, B, T) measured at 45° and 30° from striation in the extensional movement plane (see the main paper for more details). This database represents the most complete local-scale collection of Quaternary geological fault/slip data and derived kinematic and strain parameters over a large regional seismogenic and potentially seismogenic territory. The QUIN database is meant as a relatively aseptic data input for forecoming stress inversion and geodynamic modelling, fundamental for new generations of seismotectonics and seismic hazard assessment research