scholarly journals Preliminary results on the response of some springs of the Sibillini Mountains area to the 2016-2017 seismic sequence

2020 ◽  
Author(s):  
Davide Fronzi ◽  
Francesca Banzato ◽  
Stefano Caliro ◽  
Costanza Cambi ◽  
Carlo Cardellini ◽  
...  
Keyword(s):  
Central Italy ◽  
Fault System ◽  
Lower Amount ◽  
Western Slope ◽  
Seismic Events ◽  
Seismic Sequence ◽  
General Increase ◽  
Discharge Data ◽  
Groundwater Levels ◽  
Western Side

The dynamic of groundwater systems feeding several springs of the Sibillini Mountains was deeply affected by nine Mw 5.0÷6.5 seismic events occurred in central Italy starting from August 2016. The strongest shock occurred on October 30th 2016 about 5 km NNE of Norcia Town, 9 km below the surface, as a result of upper crust normal faulting on the nearly 30 km-long Mt Vettore - Mt Bove fault system, a NW-SE trending, SW-dipping fault system outcropping on the western slope of Mt Vettore, the highest peak of Sibillini Mountains. Soon after this event, a general increase of springs and rivers discharge and groundwater levels was observed both in the Visso and Norcia areas, west of the Sibillini Mountains. In the Visso area the hydrogeological changes due to the seismic sequence exhausted in the 2019, while nowadays both discharges and groundwater levels are still higher than before in the Norcia area. Discharge data of the main springs located east, south-east of the Sibillini Mountains were analysed to verify whether the general increase observed on the western side was associated to a decrease on the eastern and southern-east area. The results show that the springs located on the eastern side and southern-east side of Mt Vettore experienced a significant long-term discharge decrease. In this preliminary work, the analysis of the historical discharge series of the Pescara di Arquata spring (SE of Mt Vettore), and its relationship with the Standard Precipitation Index (SPI) shows that the very low discharge values recorded during the post-seismic period are not associated with SPI as low as documented in the past for similar discharges. Moreover, the stable isotopic composition of Pescara di Arquata water during the post-earthquake period is slightly different from that measured before the seismic events; this suggests that a lower amount of water having more enriched isotopic δ18O content reaches the spring after the seismic sequence. These aspects seem to indicate that groundwater circulation in the southern-east area of Sibillini Mountains has been affected by the 2016-2017 seismic sequence.

scholarly journals Brief communication: Co-seismic displacement on 26 and 30 October 2016 (<i>M</i><sub>w</sub> = 5.9 and 6.5) – earthquakes in central Italy from the analysis of a local GNSS network

2017 ◽  
Vol 17 (11) ◽  
pp. 1885-1892 ◽  
Author(s):  
Giorgio De Guidi ◽  
Alessia Vecchio ◽  
Fabio Brighenti ◽  
Riccardo Caputo ◽  
Francesco Carnemolla ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Central Italy ◽  
Geodetic Network ◽  
Satellite System ◽  
Fault System ◽  
Seismic Sequence ◽  
Epicentral Area ◽  
Seismic Displacement ◽  
Fault Trace ◽  
Global Navigation Satellite

Abstract. On 24 August 2016 a strong earthquake (Mw = 6.0) affected central Italy and an intense seismic sequence started. Field observations, DInSAR (Differential INterferometry Synthetic-Aperture Radar) analyses and preliminary focal mechanisms, as well as the distribution of aftershocks, suggested the reactivation of the northern sector of the Laga fault, the southern part of which was already rebooted during the 2009 L'Aquila sequence, and of the southern segment of the Mt Vettore fault system (MVFS). Based on this preliminary information and following the stress-triggering concept (Stein, 1999; Steacy et al., 2005), we tentatively identified a potential fault zone that is very vulnerable to future seismic events just north of the earlier epicentral area. Accordingly, we planned a local geodetic network consisting of five new GNSS (Global Navigation Satellite System) stations located a few kilometres away from both sides of the MVFS. This network was devoted to working out, at least partially but in some detail, the possible northward propagation of the crustal network ruptures. The building of the stations and a first set of measurements were carried out during a first campaign (30 September and 2 October 2016). On 26 October 2016, immediately north of the epicentral area of the 24 August event, another earthquake (Mw = 5.9) occurred, followed 4 days later (30 October) by the main shock (Mw = 6.5) of the whole 2016 summer–autumn seismic sequence. Our local geodetic network was fully affected by the new events and therefore we performed a second campaign soon after (11–13 November 2016). In this brief note, we provide the results of our geodetic measurements that registered the co-seismic and immediately post-seismic deformation of the two major October shocks, documenting in some detail the surface deformation close to the fault trace. We also compare our results with the available surface deformation field of the broader area, obtained on the basis of the DInSAR technique, and show an overall good fit.

scholarly journals The Campotosto linkage fault zone between the 2009 and 2016 seismic sequences of central Italy: Implications for seismic hazard analysis

2020 ◽  
Author(s):  
Emanuele Tondi ◽  
Danica Jablonská ◽  
Tiziano Volatili ◽  
Maddalena Michele ◽  
Stefano Mazzoli ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Fault Zone ◽  
Central Italy ◽  
Seismic Events ◽  
Seismic Gap ◽  
Seismic Zone ◽  
Seismic Sequence ◽  
Geological Evidence ◽  
Seismic Sequences ◽  
Seismogenic Faults

In the last decade central Italy was struck by devastating seismic sequences resulting in hundreds of casualties (i.e., 2009-L′Aquila moment magnitude [Mw] = 6.3, and 2016-Amatrice-Visso-Norcia Mw max = 6.5). These seismic events were caused by two NW-SE−striking, SW-dipping, seismogenic normal faults that were modeled based on the available focal mechanisms and the seismic moment computed during the relative mainshocks. The seismogenic faults responsible for the 2009-L′Aquila Mw = 6.3 (Paganica Fault—PF) and 2016-Amatrice-Visso-Norcia Mw max = 6.5 (Monte Vettore Fault—MVF) are right-stepping with a negative overlap (i.e., underlap) located at the surface in the Campotosto area. This latter was affected by seismic swarms with magnitude ranging from 5.0 to 5.5 during the 2009 seismic sequence and then in 2017 (i.e., a few months later than the mainshocks related with the 2016 seismic sequence). In this paper, the seismogenic faults related to the main seismic events that occurred in the Campotosto Seismic Zone (CSZ) were modeled and interpreted as a linkage fault zone between the PF and MVF interacting seismogenic faults. Based on the underlap dimension, the seismogenic potential of the CSZ is in the order of Mw = 6.0, even in the case that all the faults belonging to the zone were activated simultaneously. This has important implications for seismic hazard assessment in an area dominated by the occurrence of a major NW-SE−striking extensional structure, i.e., the Monte Gorzano Fault (MGF). Mainly due to its geomorphologic expression, this fault has been considered as an active and silent structure (therefore representing a seismic gap) able to generate an earthquake of Mw max = 6.5−7.0. However, the geological evidence provided with this study suggests that the MGF is of early (i.e., pre- to syn-thrusting) origin. Therefore, the evaluation of the seismic hazard in the Campotosto area should not be based on the geometrical characteristics of the outcropping MGF. This also generates substantial issues with earthquake geological studies carried out prior to the recent seismic events in central Italy. More in general, the 4-D high-resolution image of a crustal volume hosting an active linkage zone between two large seismogenic structures provides new insights into the behavior of interacting faults in the incipient stages of connection.

scholarly journals Conditions for the occurrence of seismic sequences in a fault system

2016 ◽  
Author(s):  
Michele Dragoni ◽  
Emanuele Lorenzano
Keyword(s):  
Elastic Half Space ◽  
The State ◽  
Fault System ◽  
Representative Point ◽  
Seismic Events ◽  
Seismic Sequence ◽  
Complex Interplay ◽  
Initial Stress State ◽  
Stress States ◽  
Stress Drops

Abstract. We consider a system made of n coplanar faults and study the conditions under which it may originate a sequence of n seismic events of similar magnitudes. The system is placed in an elastic half-space and is subject to a constant and uniform strain rate by tectonic motions. The state of the system is described by n variables that are the Coulomb stresses of the faults. Coulomb stresses increase steadily during the interseismic intervals and change suddenly in connection with seismic events. A permutation of the first n integers can be associated with each state of the system, expressing the order of Coulomb stresses according to their magnitudes. The permutation controls the evolution of the system. The state space can be divided into n! subsets corresponding to each of the n! permutations. The representative point of the system moves continuously in one of the subsets during the interseismic intervals and switches to a different subset in connection with seismic events. The order of events in a sequence can be also expressed as a permutation of the first n integers, so that the number of possible sequences is equal to n!. The order of events is determined by the initial stress state, the stress drops and the stress transfers associated with each event. If the sequence is made of n similar events and the differences between Coulomb stresses are always greater than the mutual stress transfers, the order is given by the initial permutation. However, the order implicit in the initial permutation is generally modified during the sequence, due to changes in the differences between Coulomb stresses and to different stress drops of the events. The model allows the retrieval of the stress states of a fault system from the observation of a seismic sequence. As an example, the model is applied to the 2012 Emilia (Italy) seismic sequence and enlightens the complex interplay between the fault dislocations that produced the observed order of events.

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

2019 ◽  
Vol 11 (12) ◽  
pp. 1482 ◽  
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.

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

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.

scholarly journals Historic City Centers After Destructive Seismic Events, The Case of Finale Emilia During the 2012 Emilia-Romagna Earthquake: Advanced Numerical Modelling on Four Case Studies

2017 ◽  
Vol 11 (1) ◽  
pp. 1059-1078 ◽  
Author(s):  
Simone Tiberti ◽  
Gabriele Milani
Keyword(s):  
Seismic Vulnerability ◽  
Numerical Models ◽  
Central Italy ◽  
Actual Condition ◽  
Actual State ◽  
Seismic Events ◽  
Seismic Sequence ◽  
Masonry Churches ◽  
Historic City ◽  
The Village

Introduction:The recent wave of seismic shocks in Central Italy (2016) had once more disastrous consequences for the local monuments, which consisted of old masonry churches and towers. The permanent, seismic-induced damage to cultural heritage has become a serious issue that can no longer be downsized, and questions have been raised about how to satisfactorily assess the vulnerability of such heritage in advance. This paper deals with the investigations into the actual condition of a historic city center partially destroyed by the seismic sequence occurred in May 2012 in Emilia-Romagna. Namely, the case of Finale Emilia – a small to medium-sized village located at the very center of the stricken area – is considered.Methods:Three important heritage masterpieces were numerically analyzed using Finite Element meshes to deepen the knowledge of their seismic vulnerability and try to avoid similar disasters in the future. The first structure is a masonry castle known as “Castello delle Rocche”, which underwent severe damages during the seismic sequence. The second and third examples deal with the structural analysis of two towers, both collapsed due to the quakes: the Fortified Tower of the castle and the Clock Tower of the village. The last analysis is devoted to study the seismic behavior of a medium-sized masonry church (Santa Maria del Rosario), heavily damaged by the seismic sequence and whose bell tower collapsed due to the formation of a hinge at mid-height.Results and Conclusion:Numerical models were created for all the buildings involved, and a variety of advanced analyses were carried out, including nonlinear static and dynamic ones, to have a deep insight into their expected vulnerability, also finding reasonable correspondence between the numerical results and the actual state of damage observed during the surveys made in the aftermath of the seismic events.

scholarly journals Failure Analysis of Apennine Masonry Churches Severely Damaged during the 2016 Central Italy Seismic Sequence

Buildings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 58 ◽  
Author(s):  
Francesco Clementi
Keyword(s):  
Case Studies ◽  
Central Italy ◽  
Numerical Data ◽  
Sensitivity Study ◽  
Nonlinear Material ◽  
Seismic Sequence ◽  
Nonlinear Approach ◽  
Nonlinear Static ◽  
Masonry Churches ◽  
Global And Local

This paper presents a detailed study of the damages and collapses suffered by various masonry churches in the aftermath of the seismic sequence of Central Italy in 2016. The damages will first be analyzed and then compared with the numerical data obtained through 3D simulations with eigenfrequency and then nonlinear static analyses (i.e., pushover). The main purposes of this study are: (i) to create an adequately consistent sensitivity study on several definite case studies to obtain an insight into the role played by geometry—which is always unique when referred to churches—and by irregularities; (ii) validate or address the applicability limits of the more widespread nonlinear approach, widely recommended by the Italian Technical Regulations. Pushover analyses are conducted assuming that the masonry behaves as a nonlinear material with different tensile and compressive strengths. The consistent number of case studies investigated will show how conventional static approaches can identify, albeit in a qualitative way, the most critical macro-elements that usually trigger both global and local collapses, underlining once again how the phenomena are affected by the geometry of stones and bricks, the texture of the wall face, and irregularities in the plan and elevation and in addition to hypotheses made on the continuity between orthogonal walls.

scholarly journals The Role of Faults in Groundwater Circulation before and after Seismic Events: Insights from Tracers, Water Isotopes and Geochemistry

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1499
Author(s):  
Davide Fronzi ◽  
Francesco Mirabella ◽  
Carlo Cardellini ◽  
Stefano Caliro ◽  
Stefano Palpacelli ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Central Italy ◽  
Tracer Tests ◽  
Integrated Approach ◽  
Fault System ◽  
Tectonic Structures ◽  
Fault Systems ◽  
Isotopic Analyses ◽  
Before And After

The interaction between fluids and tectonic structures such as fault systems is a much-discussed issue. Many scientific works are aimed at understanding what the role of fault systems in the displacement of deep fluids is, by investigating the interaction between the upper mantle, the lower crustal portion and the upraising of gasses carried by liquids. Many other scientific works try to explore the interaction between the recharge processes, i.e., precipitation, and the fault zones, aiming to recognize the function of the abovementioned structures and their capability to direct groundwater flow towards preferential drainage areas. Understanding the role of faults in the recharge processes of punctual and linear springs, meant as gaining streams, is a key point in hydrogeology, as it is known that faults can act either as flow barriers or as preferential flow paths. In this work an investigation of a fault system located in the Nera River catchment (Italy), based on geo-structural investigations, tracer tests, geochemical and isotopic recharge modelling, allows to identify the role of the normal fault system before and after the 2016–2017 central Italy seismic sequence (Mmax = 6.5). The outcome was achieved by an integrated approach consisting of a structural geology field work, combined with GIS-based analysis, and of a hydrogeological investigation based on artificial tracer tests and geochemical and isotopic analyses.

scholarly journals Exceedance of design actions in epicentral areas: insights from the ShakeMap envelopes for the 2016–2017 central Italy sequence

2021 ◽  
Author(s):  
Iunio Iervolino ◽  
Pasquale Cito ◽  
Chiara Felicetta ◽  
Giovanni Lanzano ◽  
Antonio Vitale
Keyword(s):  
Earthquake Engineering ◽  
Structural Damage ◽  
Structural Engineering ◽  
Central Italy ◽  
Civil Defense ◽  
Point Of View ◽  
Seismic Sequence ◽  
Ground Shaking ◽  
Motion Effect ◽  
Observed Damage

AbstractShakeMap is the tool to evaluate the ground motion effect of earthquakes in vast areas. It is useful to delimit the zones where the shaking is expected to have been most significant, for civil defense rapid response. From the earthquake engineering point of view, it can be used to infer the seismic actions on the built environment to calibrate vulnerability models or to define the reconstruction policies based on observed damage vs shaking. In the case of long-lasting seismic sequences, it can be useful to develop ShakeMap envelopes, that is, maps of the largest ground intensity among those from the ShakeMap of (selected) events of a seismic sequence, to delimit areas where the effects of the whole sequence have been of structural engineering relevance. This study introduces ShakeMap envelopes and discusses them for the central Italy 2016–2017 seismic sequence. The specific goals of the study are: (i) to compare the envelopes and the ShakeMap of the main events of the sequence to make the case for sequence-based maps; (ii) to quantify the exceedance of design seismic actions based on the envelopes; (iii) to make envelopes available for further studies and the reconstruction planning; (iv) to gather insights on the (repeated) exceedance of design seismic actions at some sites. Results, which include considerations of uncertainty in ShakeMap, show that the sequence caused exceedance of design hazard in thousands of square kilometers. The most relevant effects of the sequence are, as expected, due to the mainshock, yet seismic actions larger than those enforced by the code for structural design are found also around the epicenters of the smaller magnitude events. At some locations, the succession of ground-shaking that has excited structures, provides insights on structural damage accumulation that has likely taken place; something that is not accounted for explicitly in modern seismic design. The envelopes developed are available as supplemental material.

scholarly journals Along-strike rupture directivity of earthquakes of the 2009 L'Aquila, central Italy, seismic sequence

2015 ◽  
Vol 203 (1) ◽  
pp. 399-415 ◽  
Author(s):  
G. Calderoni ◽  
A. Rovelli ◽  
Y. Ben-Zion ◽  
R. Di Giovambattista
Keyword(s):  
Central Italy ◽  
Seismic Sequence ◽  
Rupture Directivity
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