Italy Earthquake Research Articles

Real-time coseismic deformations from adaptively tight integration of high-rate GNSS and strong motion records

SUMMARYIn traditional tight integration of high-rate GNSS and strong motion sensors, an appropriate process variance is crucial for obtaining accurate broad-band coseismic deformations. In this paper, instead of using a subjectively empirical value, we present an approach for determining the process variance adaptively based on the adaptive Kalman filter for real-time use. The performance of the approach was validated by the colocated stations collected during the 2010 Mw 7.2 earthquake in El-Mayor, 2016 Mw 7.8 earthquake in New Zealand and 2016 Mw 6.5 earthquake in central Italy. The results show that this method complements the advantages of GNSS and strong motion accelerometers and can provide more accurate coseismic waveforms especially during the strong shaking period, due to the ability of the method to adjust the process variance in real time according to the actual status of the station. In addition, this method is also free from the influence of the baseline shift. Testing of the new method for the integration of strong motion and multi-GNSS indicates that multi-GNSS has an obvious improvement in the precision while single GPS has a poor observation condition.

Guest editorial: the 2016 central Italy earthquakes

Guest editorial: the 2016 central Italy earthquakes

Visual analytics of aftershock point cloud data in complex fault systems

Abstract. Aftershock point cloud data provide direct evidence for the characteristics of underground faults. However, there has been a dearth of studies using state-of-the-art visual analytics methods to explore the data. In this paper, we present a novel interactive visual analysis approach for visualizing the aftershock point cloud. Our method employs a variety of interactive operations, rapid visual computing functions, flexible display modes, and various filtering approaches to present and explore the desired information for the fault geometry and aftershock dynamics. The case study conducted for the 2016 Central Italy earthquake sequence shows that the proposed approach can facilitate the discovery of the geometry of the four main fault segments and three secondary fault segments. It can also clearly reveal the spatiotemporal evolution of the aftershocks, helping to find the fluid-driven mechanism of this sequence. An open-source prototype system based on the approach is also developed and is freely available.

PHOTOGRAMMETRY AS A PARTICIPATORY RECOVERY TOOL AFTER DISASTERS: A GROUNDED FRAMEWORK FOR FUTURE GUIDELINES

Abstract. This paper identifies the application domain, context of use, processes and goals of low-cost street-level photogrammetry after urban disasters. The proposal seeks a synergy between top-down and bottom-up initiatives carried out by different actors during the humanitarian response phase in data scarce contexts. By focusing on the self-organisation capacities of local people, this paper suggests using collaborative photogrammetry to empower communities hit by disasters and foster their active participation in recovery and reconstruction planning. It shows that this task may prove technically challenging depending on the specifics of the collected imagery and develops a grounded framework to produce user-centred image acquisition guidelines and fit-for-purpose photogrammetric reconstruction workflows, useful in future post-disaster scenarios. To this end, it presents an in-depth analysis of a collaborative photographic mapping initiative undergone by a group of citizen-scientists after the 2016 Central Italy earthquake, followed by the explorative processing of some sample datasets. Specifically, the paper firstly presents a visual ethnographic study of the photographic material uploaded by participants from September 2016 to November 2018 in the two Italian municipalities of Arquata del Tronto and Norcia. Secondly, it illustrates from a technical point of view issues concerning the processing of crowdsourced data (e.g. image filtering, selection, quality, semantic content and 3D model scaling) and discusses the viability of using it to enrich the pool of geo-information available to stakeholders and decision-makers. Final considerations are discussed as part of a grounded framework for future guidelines tailored to multiple goals and data processing scenarios.

2016 Central Italy Earthquakes: comparison between GPS signals and low-cost distributed MEMS arrays

Abstract. Modern seismic ground-motion sensors have reached an excellent performance quality in terms of dynamic range and bandwidth resolution. The weakest point in the recording of seismic events remains spatial sampling and spatial resolution, due to the limited number of installed sensors. A significant improvement in spatial resolution can be achieved by the use of non-conventional motion sensors, such as low-cost distributed sensors arrays or positioning systems, capable of increasing the density of classical seismic recording networks. In this perspective, we adopted micro-electro mechanical system (MEMS) sensors to integrate the use of standard accelerometers for moderate-to-strong seismic events. In addition, we analyse high-rate distributed positioning system data that also record soil motion. In this paper, we present data from the 2016 Central Italy earthquakes as recorded by a spatially dense prototype MEMS array installed in the proximity of the epicentral area, and we compare the results to the signal of local 1s GPS stations. We discuss advantages and limitations of this joint approach, reaching the conclusion that such low-cost sensors and the use of high rate GPS signal could be an effective choice for integrate the spatial density of stations providing strong-motion parameters.

Understanding the interacting factors that influence social vulnerability: a case study of the 2016 central Italy earthquake.

This paper seeks to identify those areas that proved socially vulnerable to the earthquake that struck central Italy on 24 August 2016. The study involved four key steps. First, six relevant social vulnerability indicators were selected, based on previous conclusions in the literature. Second, the indicators were mapped using the inverse distance weighted interpolation method. Third, social vulnerability was assessed according to a spatial combination of the indicators. Fourth, in order to build a heterogeneity map, another approach was employed to represent the spatial variability of social vulnerability and to provide additional information on the synergistic contributions of the indicators. The results indicate that age and accessibility indicators affect the entire region under review, with highly vulnerable zones being close to small historical centres. These findings will be useful to governments, policymakers, and stakeholders with regard to implementing vulnerability mitigation strategies in Italian territories that are highly susceptible to earthquake hazards.

Tracking Modal Parameter Evolution of Different Cultural Heritage Structure Damaged by Central Italy Earthquake of 2016

The preliminary results of an ambient-vibration based investigation conducted on a large sample of historic masonry towers in the Marche region (Central Italy) are presented, with a focus on the belfry of Collegiata of Santa Maria in Visso (Italy). The assessment procedure includes full-scale ambient vibration testing, modal identification from ambient vibration responses, finite element modeling and dynamic-based identification of the uncertain structural parameters of the model. As the most doubtful parameters, the modulus of elasticity of the masonry is adjusted to achieve the experimental results with numerical model by simple operations.

Advanced Seismic Analyses of “Apennine Churches” Stroked by the Central Italy Earthquakes of 2016 by the Non-Smooth Contact Dynamics Method

The dynamic behaviour and the seismic vulnerability of different masonry “Apennine Churches”, dramatically damaged by the last shocks sequence of 2016 that occurred in Central Italy, have been studied in this paper by means of advanced 3D numerical analyses with the Discrete Element Method (DEM). Thus, a discontinuous approach has been used to assess the dynamic properties and the vulnerability of the masonry structure, through large deformations regulated by the Signorini’s law, concerning the impenetrability between the rigid bodies, and by the Coulomb’s law, regarding the dry-friction model. The major purpose of this study is to highlight that relevant data on the real structural behaviour of historical masonry can be provided through advanced numerical analyses. The comparison between the results of the numerical simulation and the survey of the existing crack pattern of the churches permitted to validate the used approach. Finally, from the results and conclusions of these cases study, it is possible to affirm that the used methodology can be applied to a wide variety of historical masonry structure in Europe.

Seismic Demand on a Unreinforced Masonry Wall Restrained by Elasto-Plastic Tie-Rods Under Earthquake Sequences

ABSTRACTExisting masonry buildings show significant vulnerability to seismic sequences. This topic has so far received limited attention, concentrated on simplified simulations of the global response, governed by in-plane wall behaviour, or on a very detailed representation of monumental buildings. This paper looks at the out-of-plane response of an ordinary-building wall restrained by an elastoplastic tie-rod under Italian seismic sequence conditions. A recently proposed model is extended to account for a flexible interface defined by its compressive strength and stiffness. Response to 30 series of four events belonging to six seismic sequences shows limited damage accumulation in most cases, with most hysteretic energy dissipated in a single plastic cycle. In these cases, we find a strong correlation between the maximum rotation and intensity measures such as peak ground acceleration, peak ground velocity and acceleration spectrum intensity. This suggests that current hazard studies are adequate and that design can be based on the features of the maximum event expected. However, exceptions are noticed for the 2016 Central Italy Earthquakes, in which the considered sequence is made of multiple mainshocks inducing significant damage accumulation, but can still be resolved by a practitioner resorting to equivalent static procedures by reducing the commonly assumed behaviour factor.

Improving Physics‐Based Aftershock Forecasts During the 2016–2017 Central Italy Earthquake Cascade

AbstractThe 2016–2017 Central Apennines earthquake sequence is a recent example of how damages from subsequent aftershocks can exceed those caused by the initial mainshock. Recent studies reveal that physics‐based aftershock forecasts present comparable skills to their statistical counterparts, but their performance remains a controversial subject. Here we employ physics‐based models that combine the elasto‐static stress transfer with rate‐and‐state friction laws, and short‐term statistical Epidemic Type Aftershock Sequence (ETAS) models to describe the spatiotemporal evolution of the earthquake cascade. We then track the absolute and relative model performance using log‐likelihood statistics for a 1‐year horizon after the 24 August 2016Mw= 6.0 Amatrice earthquake. We perform a series of pseudoprospective experiments by producing seven classes of Coulomb rate‐state (CRS) forecasts with gradual increase in data input quality and model complexity. Our goal is to investigate the influence of data quality on the predictive power of physics‐based models and to assess the comparative performance of the forecasts in critical time windows, such as the period following the 26 October Visso earthquakes leading to the 30 OctoberMw= 6.5 Norcia mainshock. We find that (1) the spatiotemporal performance of the basic CRS models is poor and progressively improves as more refined data are used, (2) CRS forecasts are about as informative as ETAS when secondary triggering effects fromM3+ earthquakes are included together with spatially variable slip models, spatially heterogeneous receiver faults, and optimized rate‐and‐state parameters. After the Visso earthquakes, the more elaborate CRS model outperforms ETAS highlighting the importance of the static stress transfer for operational earthquake forecasting.

Sequential Earthquake Damage Assessment Incorporating Optimized sUAV Remote Sensing at Pescara del Tronto

A sequence of large earthquakes in central Italy ranging in moment magnitudes (Mw) from 4.2 to 6.5 caused significant damage to many small towns in the area. After each earthquake in 2016 (24 August and 26 October), automated small unmanned aerial vehicles (sUAV) acquired valuable imagery data for post-hazard reconnaissance in the mountain village of Pescara del Tronto, and were applied to 3D reconstruction using Structure-from-Motion (SfM). In July 2018, the site was again monitored to obtain additional imagery data capturing changes since the last visit following the 30 October 2016 Earthquake. A genetic-based mission-planning algorithm that delivers optimal viewpoints and path planning was field tested and reduced the required photos for 3D reconstruction by 9.1%. The optimized 3D model provides a better understanding of the current conditions of the village, when compared to the nadir models, by containing fewer holes on angled surfaces, including an additional 17% surface area, and with a comparable ground-sampling distance (GSD) of ≈2.4 cm/px (≈1.5 cm/px when adjusted for camera pixel density). The resulting three time-lapse models provide valuable metrics for ground motion, progression of damage, resilience of the village, and the recovery progress over a span of two years.

The August 24, 2016, Central Italy Earthquake: Validation of the "Modified Utstein Template for Hospital Disaster Response Reporting" As a New Tool for Reporting Hospitals' Response to Disasters.

After-action reports analyze events and improve knowledge about how to prevent and react to unexpected situations. Anyway, there is no consensus among the templates developed for disaster events reporting, and there is not a specific model for reporting hospital disaster response. The study was aimed to pilot the use of a new assessment tool for hospital response to natural disasters. A data collection tool, focused on hospital disaster response to natural disasters, was created modifying the "Utstein-Style Template for Uniform Data Reporting of Acute Medical Response in Disasters" and tested the reaction of the nearest hospitals to the epicenter after the August 24, 2016, Central Italy earthquake. Four hospitals were included. The completion rate of the tool was 97.10%. A total of 613 patients accessed the 4 emergency departments, most of them in Rieti Hospital (178; 29.04%). Three hundred thirty-six (54.81%) patients were classified as earthquake-related, most with trauma injuries (260; 77.38%). This template seemed to be a valid instrument for hospital disaster management reporting and could be used for better comprehension of hospital disaster reaction, debriefing activities, and hospital disaster plan revisions.

Effectiveness of different base isolation systems for seismic protection: Numerical insights into an existing masonry bell tower

Recent earthquakes in Italy have emphasized the high seismic vulnerability of historical masonry constructions and the need of effective retrofitting interventions. This paper investigates the possibility of improving the seismic performance of a historical masonry bell tower using different types of commercial isolators: High Damping Rubber Bearing (HDRB), Lead Rubber Bearing (LRB) and Friction Pendulum System (FPS) Isolator. Detailed three-dimensional (3D) finite element (FE) models are created to characterize the behavior of the three types of isolators. Then, an Abaqus User Element (UEL) is used to represent the 3D behavior of the isolators for global seismic analyses of isolated structures. The results of cyclic shear analyses show that the proposed UEL model can accurately predict the behavior obtained through detailed 3D FE models. Non-linear dynamic analyses are performed to investigate the seismic response of the historical masonry bell tower in the original and base-isolated configurations subjected to moderate-to-high seismic actions: moreover, the effects of near fault earthquakes are analyzed. The results obtained from the numerical simulations show that the HDRBs do not ensure an adequate seismic protection of the masonry bell tower in terms of damage patterns and top displacements. On the other hand, the LRBs and FPS isolators are very effective in reducing the earthquake effects on the masonry tower: residual displacements are negligible and the isolator displacements are limited. In case of near fault earthquakes, an isolation system with higher damping and larger dimension is required to reduce the drifts of the tower and to accommodate the large displacements of the isolators.

Post-traumatic stress disorder, emotional and behavioral difficulties in children and adolescents 2 years after the 2012 earthquake in Italy: an epidemiological cross-sectional study.

Despite the occurrence of several earthquakes, only a few studies were conducted in Italy on the psychological impact in children and adolescents, with data mostly collected within one year after the disaster. This cross-sectional study aimed at exploring the prevalence of both post-traumatic stress disorder (PTSD) and emotional/behavioral difficulties, as well as at identifying their main predictors, among youths 2 years after the earthquake that hit Northern Italy in 2012. 682 children and adolescents (9-14years) living in two districts (earthquake zone vs control zone) were administered an exposure questionnaire, the UCLA PTSD-Index for DSM-IV, and the Strengths and Difficulties Questionnaire (SDQ) and 1162 parents were assessed through the Symptom Checklist-90 (SCL-90). The prevalence of a likely PTSD in the earthquake zone was 1.9% (4.4% near the epicenter) and the total PTSD score in the affected area was significantly higher than in the control zone. 14.9% of youths living in the earthquake zone had a borderline/abnormal SDQ total difficulties score and 87.5% of youth with a likely PTSD also had a SDQ total score in the borderline/abnormal range. Regression analysis showed that the number of lifetime traumatic events (e.g., death of a relative) was the best predictor of children/adolescents psychological difficulties 2years after the earthquake, followed by severity of exposure (personal injuries and losses) and parental psychopathology. Despite some limitations, this study highlights that youths may exhibit PTSD symptoms years after disasters, often in comorbidity with behavioral/emotional difficulties, stressing the need for long-term surveillance and interventions in exposed populations.

Dialogical strategies in replies to offensive humour

AbstractThe aim of this paper is to determine whether humour can be used as a discursive strategy to reply to offensive humour about natural disasters and what purpose it serves. A corpus of 431 replies to the Charlie Hebdo cartoons concerning the earthquake in central Italy in August 2016 was analysed. Depending on the target of the humour in these replies, they were used to agree, disagree or deflect away from the offensive and aggressive content of the cartoons. The results show that humour can be used as a discursive strategy to respond to offensive humour. Moreover, an analysis of the corpus revealed that humorous replies were used mainly to agree rather than disagree with the cartoons.

Deterministic Variability of the Ionosphere on the Eve of Strong (M ≥ 6) Earthquakes in the Regions of Greece and Italy According to Long-Term Measurements Data

Abstract—Specific features of the variation in the electron concentration in the ionosphere in front of strong (M ≥ 6) earthquakes in the most seismically active areas of Europe, Greece and Italy, are considered on the basis of long-term measurements. Vertical sounding data (variations of the critical frequency foF2) are analyzed to cover long periods of time before the GPS/GLONASS era, and variations of the vertical total electronic content are also analyzed with the advent of global navigation satellite systems receivers in the considered regions. This analysis is based on the results of previous publications that revealed features of ionospheric precursors such as self-similarity, which is expressed in the exceptional stability of electron concentration variation as dependence on the local time. Its graphic representation is called the ionospheric precursor mask. This stability, which is defined as deterministic variability, is confirmed by the multiyear measurement data presented in this work. One new result involves the regional features of the ionospheric precursor mask found for Italy, where the mask for earthquakes in central Italy (within a radius of 300 km north of Rome) and the mask for earthquakes in southern Italy (within a radius of 300 km south of Rome) differ in phase. A possible explanation of the observed regional features is proposed.

Coulomb pre-stress and fault bends are ignored yet vital factors for earthquake triggering and hazard

Successive locations of individual large earthquakes (Mw > 5.5) over years to centuries can be difficult to explain with simple Coulomb stress transfer (CST) because it is common for seismicity to circumvent nearest-neighbour along-strike faults where coseismic CST is greatest. We demonstrate that Coulomb pre-stress (the cumulative CST from multiple earthquakes and interseismic loading on non-planar faults) may explain this, evidenced by study of a 667-year historical record of earthquakes in central Italy. Heterogeneity in Coulomb pre-stresses across the fault system is >±50 bars, whereas coseismic CST is <±2 bars, so the latter will rarely overwhelm the former, explaining why historical earthquakes rarely rupture nearest neighbor faults. However, earthquakes do tend to occur where the cumulative coseismic and interseismic CST is positive, although there are notable examples where earthquake propagate across negatively stressed portions of faults. Hence Coulomb pre-stress calculated for non-planar faults is an ignored yet vital factor for earthquake triggering.

Validation and extension of a statistical usability model for unreinforced masonry buildings with different ground motion intensity measures

Predicting the usability of a building, i.e. its condition of being occupiable after a seismic event, is relevant both in a post-emergency situation and within a risk-reduction policy. In the past an empirical model was proposed, involving the computation of a usability index based on macroseismic intensity and on seven building parameters, combined by means of regression coefficients and weights. The statistical model was calibrated on data of about 60,000 buildings affected by the 2009 L’Aquila earthquake in Italy. Therefore, it is useful to validate the model against data from the 2002 Molise earthquake in Italy. Good agreement between predicted and observed usability is shown, despite the fact that in 2002, macroseismic intensity was attributed to an entire municipality instead of a more limited area. Moreover, given the current availability of the shakemaps for the 2009 event, a novel model replacing conventional macroseismic intensity by an instrumental intensity measure is proposed. Three ground motion parameters are considered here: peak ground acceleration, peak ground velocity, and spectral pseudoacceleration at a period of vibration of 0.3 s. The model has been streamlined by reducing the building parameters from seven to five: building position within the structural aggregate, roof type, construction timespan, structural class, and pre-existing damage to structural elements. Peak ground acceleration and spectral pseudoacceleration are shown to be less effective than peak ground velocity in predicting observed usability. Therefore, usability probability matrices are computed in terms of peak ground velocity; the model is presented with all necessary coefficients and weights, and a worked-out example shows how to apply the procedure.

Seismic Vulnerability of Buildings in Historic Centers: From the “Urban” to the “Aggregate” Scale

Seismic vulnerability assessment of urban centers is a challenging issue that needs to be faced accurately for the earthquake risk of large territorial areas. The selection of suitable methods is a crucial aspect that must be treated according to different evaluation processes, depending on the size of the problem and on the available calculation capacities. A possible strategy consists in analyzing large stocks of buildings, so to include in the analyses all those structural parameters that characterize their response and to involve the variability of the considered features. This would require a high computational effort that should be addressed to the investigation of the response of a large number of models. For this reason, simplified procedures based on engineeristic judgements, are commonly considered a viable way to be undertaken in order to predict damage scenarios. Alternatively, the attention could be focused on a limited number of buildings that are judged to be representative of the whole stock. In this case, more sophisticated analyses could be carried out and the obtained results could be extended to the whole urban center. Based on this premise, this paper presents the results obtained through the application of two different seismic vulnerability methodologies on the historic center of Campotosto, in Italy, which was hit by the last 2016 Central Italy earthquake. The first is an empirical method, applied considering a large stock of 130 buildings, which was calibrated by the authors after the 2009 L’Aquila earthquake for historical centers that are similar to the one studied in this paper. The latter, is a method based on analytical formulations dealt with by the Vulnus software, developed at the University of Padua in Italy, which was used for evaluating the seismic vulnerability of an aggregate building, which has been considered representative of the historic center. The final aim is to compare, also in the light of the damage observed after the 2016 earthquake, the damage scenarios, expressed in terms of fragility curves, derived from the two applied methodologies, in order to prove their reliability and to stress the possible issues related to their implementation at different scales.

The Nature of \u201cNatural Disasters\u201d: Survivors\u2019 Explanations of Earthquake Damage

The distinction between natural and human-made disasters is ingrained in everyday language. Disaster scientists have long been critical of this dichotomy. Nonetheless, virtually no attention has been paid to how disaster survivors conceptualize the causes of the disasters they experience. In this mixed-methods longitudinal study, 112 survivors of the 2016–2017 Central Italy earthquakes completed questionnaires 3 and 16 months following the earthquakes, with the aim of assessing attributions of blame for the earthquake damage. In-depth interviews were also conducted with 52 participants at the 3-month mark to explore representations of causation for the earthquake damage. The distinction between disasters caused by nature and disasters caused by humans was not supported by survivors of the earthquake. In the longitudinal surveys, building firms and the State were assigned as much blame as nature for the earthquake damage, at both 3 months and 16 months after the earthquakes. Corroborating this complexity, in the interviews, the causes of the earthquake damage, rather than being understood as purely natural, were perceived as a complex mosaic composed of political, technological, natural, and moral factors. This empirical work shows that disaster survivors combine both nature-based and human-based explanations of disasters, rather than subscribing to one or the other. These findings have practical implications for disaster risk reduction and response.