Macroseismic Scale Research Articles

INSAR-BASED DETECTION AND MAPPING OF SEISMICALLY INDUCED GROUND SURFACE DISPLACEMENT AND DAMAGE IN PAMPANGA, PHILIPPINES

On April 22, 2019, an earthquake with a magnitude MW 6.1 struck the municipality of Castillejos in Zambales, the Philippines, and severely affected the province of Pampanga, which caused damage to commercial and residential structures reaching over 40 victims. This paper presents an approach for creating a pixel-based proxy damage assessment and displacement field maps to delineate the extent of ground surface displacements due to an earthquake. Specifically, this paper explored two change detection methods: the interferometric synthetic aperture radar (InSAR) technique and the coherence difference analysis method, using an open-source remote sensing software package and free SAR image data acquired by Sentinel-1 missions. Ground truth data were collected to substantiate the findings of the generated maps after the earthquake. Out of 7 surveyed damaged structures that were included in the National Disaster Risk Reduction and Management Council (NDRRMC) of the Philippines Situational Report, four damaged structures were successfully targeted using the proxy damage assessment map that had a coherence difference value ranging from 0.7-0.9 and damage grades of 3-5 based on the European Macroseismic Scale 1998 (EMS-98) damage classification system. This study confirms that change detection methods applied to C-band Sentinel-1 SAR data are valuable for mapping damaged areas and estimating ground surface displacements toward better hazard mitigation and disaster response.

Fifteen years of Environmental Seismic Intensity (ESI-07) scale: Dataset compilation and insights from empirical regressions

The Environmental Seismic Intensity scale (ESI-07), published 15 years ago under the umbrella of INQUA (International Union for Quaternary Research), is solely based on earthquake effects on the natural environment. ESI-07 provides complementary information with respect to other macroseismic scales, in particular those stemming from the original Mercalli scale, which are mainly based on effects on manmade structures. We collect information on 157 earthquakes, occurred between 300 AD and 2020, that have been studied using the ESI-07 scale. The ESI-07 epicentral intensity can be assigned based on linear or areal features (e.g., length of surface rupture, area affected by environmental effects); this value is generally in good agreement, or slightly larger, than estimates provided using other macroseismic scales. Higher discrepancies are found for earthquakes with ESI-07 epicentral intensity above X, where other scales tend to saturate, as expected based on the original definition of the Mercalli-family intensity scales. We develop scaling relations among ESI-07 epicentral intensity and moment magnitude, surface rupture length and affected area. After critically evaluating the scientific literature, we argue that the ESI-07 reached its original goals and proved to be particularly useful for the documentation of earthquake damage i) in remote regions, ii) in the case of strong events, where other scales saturate, and iii) in the region closer to the epicenter. Finally, we identify gaps where to focus future efforts, such as the integration of remote sensed datasets in ESI-07 assignment and the refinement of empirical regressions.

Comparison of vulnerabilities in typical bridges using macroseismic intensity scales

The macroseismic intensity scale in different regions is extensively assessed in the vulnerability assessment of building structures and is rarely used to quantify the damage characteristics of group bridges. To more accurately examine the differences in the seismic vulnerability of typical bridges in an earthquake-damaged region under multiple intensity scales, this study analyses the vulnerability of 1516 girder bridges and 612 arch bridges affected by the Wenchuan earthquake, which occurred on May 12, 2008, in China, by using the European Macroseismic scale, Medvedev, Sponheuer, and Karnik scale, and the Chinese Seismic Intensity scale based on the principle of nonlinear regression and probability models. The vulnerability matrices, functions, and curves of the update models to compare girder bridges and arch bridges were obtained based on the number of samples and their failure ratio. When combined with the new cumulative exceeding probability model, curves of the exceeding probability model of girder bridges and arch bridges under the different intensity scales were obtained and compared. A parameter matrix model is proposed to evaluate and predict the seismic vulnerability of regional bridges. Combined with empirical data on the seismic damage caused to the girder bridges and arch bridges in the earthquake, their vulnerability matrices, curves, and point cloud models were obtained under a multi-intensity scale of assessment for a comparative analysis. The conclusions of this study can be used for an accurate assessment of the vulnerability of typical bridges in the future.

Seismic vulnerability assessment of minor Italian urban centres: development of urban fragility curves

This paper presents a novel hybrid-based methodology devoted to develop urban fragility curves and damage probability matrices to predict likelihood seismic damage scenarios for small and medium Italian urban centres, considering URM buildings only. The concept of urban fragility curve consists of a single curve mean-representative of the seismic fragility of an entire area accounting for the combinations of building classes and their percentage, then they differ from those typological. The methodology has been developed with reference to Rocca di Mezzo, a small Italian urban centre located in the central Apennine area, Italy. Based on CarTiS inventory, building classes have been firstly recognized and urban fragility curves, representative for damage scenarios at Ultimate Limit State, developed. To predict damage scenarios from low to high-intensity earthquakes, an approach to define multi-damage urban fragility curves and damage probability matrices has been also presented. To this aim, a damage scale suffered by building classes has been defined by converting the final outcomes of the AeDES form (used in Italy for post-earthquake surveys) in the damage levels provided by the European Macroseismic Scale (EMS98). Data coming from urban fragility curves have been compared with the actual damage scenario recorded in Rocca di Mezzo after the 2009 L’Aquila’s earthquake, in terms of both peak-ground acceleration and Mecalli-Cancani-Sieberg scale. The achieved results showed a good accordance between theoretical predictions and actual damage scenarios, coherent also with the damage scenarios occurred in other Italian historical centres hit by severe earthquakes over the years. Thus, the methodology can provide a first important indicator to support the development of emergently plans devoted to identify priority of interventions in such areas particularly vulnerable with respect to others.

Vibration-Based and Near Real-Time Seismic Damage Assessment Adaptive to Building Knowledge Level

This paper presents a multi-level methodology for near real-time seismic damage assessment of multi-story buildings, tailored to the available level of knowledge and information from sensors. The proposed methodology relates changes in the vibratory characteristics of a building—evaluated via alternative dynamic identification techniques—to the European Macroseismic Scale (EMS-98) damage grades. Three distinct levels of knowledge are considered for the building, with damage classification made through (i) empirical formulation based on quantitative ranges reported in the literature, (ii) analytical formulation exploiting the effective stiffness concept, and (iii) numerical modelling including a simplified equivalent single-degree-of-freedom model or a detailed finite element model of the building. The scope of the study is twofold: to construct a framework for integrating structural health monitoring into seismic damage assessment and to evaluate consistencies/discrepancies among different identification techniques and model-based and model-free approaches. The experimental data from a multi-story building subject to sequential shaking are used to demonstrate the proposed methodology and compare the effectiveness of the different approaches to damage assessment. The results show that accurate damage estimates can be achieved not only using model-driven approaches with enhanced information but also model-free alternatives with scarce information.

INGe: Intensity-ground motion data set for Italy

In this paper we present an updated and homogeneous earthquake dataset for Italy compiled by joining the intensities available in the Italian Macroseismic Database DBMI15 and the peak ground motion (PGM) parameters present in the Engineering Strong-Motion (ESM) accelerometric data bank. The database has been compiled through an extensive procedure of evaluation and revision based on two main steps: 1) the selection of the earthquakes in DBMI15 with homogeneous macroseismic intensities in terms of data sources and 2) the extraction of all the localities reporting intensity data which are located within 3 km from the accelerograph stations that recorded the data. The final dataset includes 519 intensity-PGM data pairs from 65 earthquakes and 227 stations in the time span 1972–2016. The reported intensities are expressed either in the Mercalli-Cancani- Sieberg (MCS) or the European macroseismic (EMS-98) scales. The events are characterized by magnitudes in the range 4.1–6.8 and depths in the range 0–55 km. Here, we illustrate the data collection and the properties of the database in terms of recording, event and station distributions as well as macroseismic intensity points. Furthermore, we discuss the most relevant features of engineering interest showing several statistics with reference to the most significant metadata (such as moment magnitude, several distance metrics, style of faulting etc). The dataset is expected to be useful for benchmarking existing and for developing new ground motion intensity conversion equations offering a common basis, and sparing the time and effort required for assembling to the interested researchers. The dataset is available at https://zenodo.org/record/4623732#.YNX-AZMzbdc.

Influence of construction age on seismic vulnerability of masonry buildings damaged after 2009 L'Aquila earthquake

The aim of this study is to describe the evolution of vulnerability over the years for masonry buildings characterized by a good quality layout and/or a regular texture. To this aim, data collected shortly afterwards the L'Aquila 2009 earthquake are considered, recently released by the Italian Department of Civil Protection (DPC) through the Da.D.O. (Database di Danno Osservato, Database of Observed Damage) platform (Dolce et al., 2019) [1].The taxonomy has been defined reflecting the need to consider all the parameters available from post-earthquake inspections and the obtainment of reliable and homogeneous sample.A time-consuming data processing has been performed to obtain a generalized version of the original database, which has been integrated with census data to avoid bias in vulnerability analysis. Then, damage analysis has been done considering 5 + 1 damage grades defined for the whole building based on the conversion of damage for vertical structures in sight of the classification of European Macroseismic Scale. The analysis of mean damage values reveals the general trends as a function of the main influential parameters, i.e. construction age and horizontal structural types, having fixed the vertical structural type and the quality layout.Vulnerability curves were derived assuming a lognormal statistical model and peak ground acceleration as intensity measure, through a minimization procedure of the distance between predicted and observed mean damage.In addition, the general criteria established to define the taxonomy had allowed to accomplish a direct comparison also between vertical structures, namely buildings with good quality and regular texture analysed herein and those with bad quality and irregular layout thoroughly analysed in Del Gaudio et al. (2021) [2]; fully characterizing the behaviour of masonry buildings under lateral loads.

The damaging character of shallow 20th century earthquakes in the Hainaut coal area (Belgium)

Abstract. The present study analyses the impact and damage of shallow seismic activity that occurred from the end of the 19th century until the late 20th century in the coal area of the Hainaut province in Belgium. This seismicity is the second-largest source of seismic hazard in north-western Europe after the Lower Rhine Embayment. During this period, five earthquakes with moment magnitudes (Mw) around 4.0 locally caused moderate damage to buildings corresponding to maximum intensity VII on the European Macroseismic Scale 1998 (EMS-98). Reviewing intensity data from the official macroseismic surveys held by the Royal Observatory of Belgium (ROB), press reports and contemporary scientific studies resulted in a comprehensive macroseismic intensity dataset. Using this dataset, we created macroseismic maps for 28 earthquakes, established a new Hainaut intensity attenuation model and a relationship linking magnitude, epicentral intensity and focal depth. Using these relationships, we estimated the location and magnitude of pre-1985 earthquakes that occurred prior to deployment of the modern digital Belgian seismic network. This resulted in a new updated earthquake catalogue for the Hainaut area for the 1887–1985 period, including 124 events. A comparison with other areas worldwide where currently similar shallow earthquake activity occurs suggests that intensity attenuation is strong in Hainaut. This high attenuation and our analysis of the cumulative effect of the Hainaut seismicity indicate that current hazard maps overestimate ground motions in the Hainaut area. This reveals the need to use more appropriate ground motion models in hazard issues. Another strong implication for earthquake hazard comes from the reliability of the computed focal depths that helps clarifying the hypotheses about the origin of this seismicity. Some events were very shallow and occurred near the surface up to a depth not exceeding 1 km, suggesting a close link to mining activities. Many events, including the largest shallow events in the coal area before 1970, occurred at depths greater than 2 km, which would exclude a direct relationship with mining, but still might imply a triggering causality. A similar causality can also be questioned for other events that occurred just outside of the coal area since the end of the mining works.

Census-Based Typological Damage Fragility Curves and Seismic Risk Scenarios for Unreinforced Masonry Buildings

Seismic risk assessment has become a crucial issue for optimal management of economic resources allocated to mitigation. For this purpose, in the last decades, several research activities were aimed to update hazard, exposure, and vulnerability models that contribute to seismic risk assessment. From this perspective, the present work focuses on developing new empirical damage fragility curves for census-based typological unreinforced masonry buildings. In particular, damage data observed after the 2009 L’Aquila earthquake, Italy, related to almost 57,000 residential buildings, were used to calibrate the fragility functions. These data were complemented with the census data with the aim of obtaining an accurate estimation of the number of undamaged buildings. Damage fragility curves were identified for typological building classes, defined considering parameters present in both post-earthquake observations and census data with the aim of extending the results to the whole national territory. Six typological classes were defined considering the categories of the construction timespan and of the state of repair parameters. Then, a further distinction of the typological classes considering the number of stories parameter was included where relevant. The fragility curves were defined as a function of peak ground acceleration for five damage states, defined according to the European macroseismic scale. The results confirmed that older buildings are more vulnerable than newer ones and highlighted the crucial role of the state of repair on the damage fragility curves. Finally, the new set of damage fragility functions was uploaded in the Italian Risk Maps information technology platform, used by the Civil Protection Department for risk evaluation, as an exemplification of the potential application of the fragility curves.

Multi-risk assessment in a historical city

Natural hazards pose a significant threat to historical cities which have an authentic and universal value for mankind. This study aims at codifying a multi-risk workflow for seismic and flood hazards, for site-scale applications in historical cities, which provides the Average Annual Loss for buildings within a coherent multi-exposure and multi-vulnerability framework. The proposed methodology includes a multi-risk correlation and joint probability analysis to identify the role of urban development in re-shaping risk components in historical contexts. The workflow is unified by exposure modelling which adopts the same assumptions and parameters. Seismic vulnerability is modelled through an empirical approach by assigning to each building a vulnerability value depending on the European Macroseismic Scale (EMS-98) and modifiers available in literature. Flood vulnerability is modelled by means of stage-damage curves developed for the study area and validated against ex-post damage claims. The method is applied to the city centre of Florence (Italy) listed as UNESCO World Heritage site since 1982. Direct multi-hazard, multi-vulnerability losses are modelled for four probabilistic scenarios. A multi-risk of 3.15 M€/year is estimated for the current situation. In case of adoption of local mitigation measures like floodproofing of basements and installation of steel tie rods, multi-risk reduces to 1.55 M€/yr. The analysis of multi-risk correlation and joint probability distribution shows that the historical evolution of the city centre, from the roman castrum followed by rebuilding in the Middle Ages, the late XIX century and the post WWII, has significantly affected multi-risk in the area. Three identified portions of the study area with a different multi-risk spatial probability distribution highlight that the urban development of the historical city influenced the flood hazard and the seismic vulnerability. The presented multi-risk workflow could be applied to other historical cities and further extended to other natural hazards.

Phenological and seismological impacts on airborne pollen types: A case study of Olea pollen in the Region of Murcia, Mediterranean Spanish climate

The rationale of this paper was to investigate whether earthquakes impact airborne pollen concentrations, considering some meteorological parameters. Atmospheric pollen concentrations in the Region of Murcia Aerobiological Network (Spain) were studied in relation to the occurrence of earthquakes of moment magnitude (up to Mw = 5.1) and intensity (intensity up to grade VII on the European Macroseismic Scale). In this study, a decade (2010–2019) was considered across the cities of the network. Earthquakes were detected in 12 out of 1535 days in the Olea Main Pollen Season in Cartagena, 49 out of 1481 days in the Olea Main Pollen Season in Lorca, and 39 out of 1441 days in the Olea Main Pollen Season in Murcia. The Olea pollen grains in this network were attributed to the species Olea europaea, i.e., the olive tree, a taxon that appears widely in the Mediterranean basin, in both cultivated and wild subspecies. Differences between the Olea concentration on days with and without earthquakes were only found in Lorca (Kruskal-Wallis: p-value = 0.026). The low frequency and intensity of the earthquakes explained these results. The most catastrophic earthquake felt in Lorca on May 11th, 2011 (IVII, Mw = 5.1, 9 casualties) did not result in clear variations in pollen concentrations, while meteorology (e.g., African Dust Outbreak) might have conditioned these pollen concentrations. The research should be broadened to other active seismological areas to reinforce the hypothesis of seismological impact on airborne pollen concentrations.

Relationships between empirical damage and direct/indirect costs for the assessment of seismic loss scenarios

The definition of relationships between damage and losses is a crucial aspect for the prediction of seismic effects and the development of reliable models to define risk maps, loss scenarios and mitigation strategies. The paper focuses on the analysis of post-earthquake empirical data to define relationships between buildings’ damage expressed as usability rating or as global damage state and the associated costs for repair (i.e. direct costs) or for population assistance (i.e. a part of total indirect costs). The analysis refers to the data collected on residential buildings damaged by 2009 L'Aquila earthquake. For different usability rating or damage states, the paper presents the costs expressed in terms of percentage with respect to the reference unit cost of a new building (%Cr and %Ca for repair and population assistance costs, respectively). In particular, the costs analysis refers to undamaged, lightly or severely damaged buildings classified according to usability rating (i.e. A, B-C or E according to Italian classification) or to five different global Damage States (DSs). DSs comply with European Macroseismic Scale (EMS-98) and derive from literature available matrices properly defined to convert empirical damage to structural and non-structural components into building global damage. The %Cr probability density functions and relevant statistics derive from the analysis of actual data of post-earthquake reconstruction process, while, to determine those related to %Ca, a deep analysis of population assistance types, person/month assistance cost for each assistance form, and a methodology to associate such costs to each building are herein presented and discussed. Finally, the paper presents a relationship calibrated on empirical data to directly correlate repair costs on a building with assistance costs to their occupants. The relationships between empirical damage and direct and indirect costs herein presented are of paramount importance because they allow reliable loss scenarios to be defined by simply using literature fragility curves (defined according to empirical or mechanical approaches) aimed at evaluating the probability of exceeding different usability rating or damage states of existing buildings.

Assessment of Seismic Vulnerability of Reinforced Concrete Building Frames Based on European Macroseismic Scale (Case Study of Siak Regency Government Building)

Earthquake disasters in Indonesia are currently not only experienced in areas that often occur earthquakes, in areas that were once relatively safer also experienced earthquakes. The greater the strength of the earthquake in one area the greater the scope of the area affected by the earthquake. Riau Province, especially the Siak Regency, is one of the areas that are in a relatively safe zone. However, it can still experience an earthquake if the point of the earthquake is near the area itself or because the earthquake point has a very large area achievement due to the magnitude of the strength of the earthquake itself. Lately to evaluate buildings that have been standing, rapid assessment of vulnerability or rapid screening. One of the commonly used rapid vulnerability assessment procedures is that issued by FEMA. However, often the assessment of buildings provided by regulations, such as FEMA is less applicable to parties or communities not of civil engineering background, the procedures are complicated or cannot be underestimated for various disaster cases. So that academics in some countries develop vulnerability assessments that do not involve much mathematical analysis, simple, can be used by parties who are not of technical background, can be used in many countries, and can also be used for disasters other than seismic disasters/earthquakes. One such method of vulnerability assessment is the assessment procedures that are founded by the European Seismic Scale. Test results showed that vulnerability assessments could quickly be carried out by researchers with no civilian background. So that this calculation can be done by even ordinary people. This is very helpful for the assessment of the building against the damage caused by the earthquake.

Seismic response of masonry buildings in historical centres struck by the 2016 Central Italy earthquake. Calibration of a vulnerability model for strengthened conditions

Brought to light by the 1997 Umbria-Marche (Italy) earthquake for the first time, the theme of damage patterns of masonry buildings with structural interventions became urgent again in the 2016–17 Central Italy seismic swarm. On a sample of 2306 buildings within the seismic field, the 85% bears the signs of structural interventions.With the aim of inferring the vulnerability factors from damage of strengthened buildings, a close-up analysis revealed that interventions can cause damage to the structures on which they are applied because of i) poor detailing and ii) incompatibility among parts, old and new. These conditions limited the attainment of a building’s box-like behaviour and, therefore, an unfavourable contribution of interventions was identified. Conversely, a favourable contribution was determined.The analytic comparison between the behaviour of building types with interventions and that of the vulnerability classes of the European Macroseismic Scale (EMS-98) obtained a vulnerability model for empirical data. Buildings whose interventions had an unfavourable contribution are comparable with ‘original’, unreinforced ones; conversely, a favourable contribution permitted them to approach the behaviour of modern masonry structures.This work represents a first step towards the inclusion of strengthened buildings in the EMS-98 vulnerability system.

Evolution of the seismic vulnerability of masonry buildings based on the damage data from L'Aquila 2009 event

The purpose of this study is the analysis of vulnerability trends, with particular emphasis to the evolution of the seismic behaviour of masonry buildings over the years due to the improvements in construction practices and to the enhancement of building materials over the years, also related to the subsequent enactment of seismic prescriptions. To this aim, residential masonry buildings damaged after the 2009 L'Aquila earthquake are considered, coming from the online platform Da.D.O. (Database di Danno Osservato, Database of Observed Damage) recently released from the Italian Department of Civil Protection. General features of all the parameters available from the original database are thoroughly analysed, a selection of which is used for vulnerability analysis, namely the period of construction and the design type, the presence of structural interventions, the type of horizontal structure. Vulnerability curves are obtained through an optimization technique, minimizing the deviation between observed and predicted damage. PGA from ShakeMap is used for ground motion characterization. Damage levels defined according to the European Macroseismic Scale are considered, obtained from the observed damage for vertical structures collected during the inspections. Vulnerability curves are firstly obtained as a function of period of construction and horizontal structural types, limited to the irregular layout and bad quality vertical type only, highlighting their clear influence on seismic behaviour. Lastly, the effectiveness of retrofit intervention is evaluated comparing the vulnerability curves for strengthened masonry buildings compared to those not subjected to any retrofit interventions.

The Influence of the Rate of Increase of Ground Vibration Accelerations During Earthquakes on the Value of the Observed Macroseismic Effect

Aims:It is known that along with the traditionally considered amplitudes and durations of ground vibrations, the rate of increase in the intensity of ground vibrations in time can also affect the level of macroseismic effects caused by earthquakes. According to the previously obtained correlations, the differences between the observed macroseismic effects during earthquakes with slow and fast increases in the amplitude level of oscillations can reach one point of the macroseismic scale. The purpose of these study is to obtain, on the basis of a significantly (almost 9 times) larger than before, the volume of initial data (in combination with a more effective method of analysis) new and more accurate quantitative estimates of the studied dependences, as well as their possible interpretation.Background:The work continues the research began in 1985-1989. A representative statistical material was used, including 1250 accelerograms of earthquakes that occurred in different regions of the world, with magnitudesM= 2.5-7.7, distances of 5-230 km and independent estimates of macroseismic intensitiesI= 3-10 points by theMSKorMMI.Objective:Correlations between the absolute and relative rates of increase of ground vibration accelerations during earthquakes with different magnitudes and distances, on the one hand, and macroseismic effects caused by these vibrations, on the other, are considered.Methods:The study was carried out in the form of a direct statistical comparison of the parameters describing the form of ground vibrations during earthquakes with the characteristics of variations in macroseismic effects caused by these vibrations. A sample was formed and analyzed, including 1250 accelerograms of sensible and strong earthquakes recorded in various regions of the world and having independent estimates of the macroseismic intensity of shaking at instrumental registration sites.Results:It is shown that the macroseismic intensity of shaking can depend on the relative rate of increase of acceleration amplitudes in the general wavetrain of ground vibrations. An increase in the macroseismic intensity of shaking was observed with an increase in the relative rate of increase of the amplitudes and, conversely, it decreases with a slowdown in the rate of increase of the acceleration intensity. Similar constructions, made according to the data of the Time-Frequency Signal Analysis (TFSA) of 50 accelerograms of earthquakes withM= 3.3-6.2, a distance of 7-139 km and a macroseismic intensity of 4-7MMIpoints, showed the same dependence, but clearer and with large coefficients of regression and correlation. The difference between earthquakes with “fast” and “slow” accelerations in the intensityIcan reach oneMSKpoint.Conclusion:The results of this study indicate that the rate of increase in the acceleration of ground vibrations during earthquakes can in a certain way affect the macroseismic effects. Earthquakes with slowly increasing amplitudes of ground vibration accelerations form average less macroseismic effects than those with rapidly growing accelerations.Variations in the shaking intensity, at the same time, are quite significant and can be compared with variations associated with differences in soil-geomorphological conditions, focal mechanisms, general seismotectonic conditions and other factors that are traditionally taken into account in detailed assessments of seismic hazard. Therefore, this factor should also be taken into account when conducting such studies.

Seismic Damage Semantics on Post-Earthquake LOD3 Building Models Generated by UAS

In a post-earthquake scenario, the semantic enrichment of 3D building models with seismic damage is crucial from the perspective of disaster management. This paper aims to present the methodology and the results for the Level of Detail 3 (LOD3) building modelling (after an earthquake) with the enrichment of the semantics of the seismic damage based on the European Macroseismic Scale (EMS-98). The study area is the Vrisa traditional settlement on the island of Lesvos, Greece, which was affected by a devastating earthquake of Mw = 6.3 on 12 June 2017. The applied methodology consists of the following steps: (a) unmanned aircraft systems (UAS) nadir and oblique images are acquired and photogrammetrically processed for 3D point cloud generation, (b) 3D building models are created based on 3D point clouds and (c) 3D building models are transformed into a LOD3 City Geography Markup Language (CityGML) standard with enriched semantics of the related seismic damage of every part of the building (walls, roof, etc.). The results show that in following this methodology, CityGML LOD3 models can be generated and enriched with buildings’ seismic damage. These models can assist in the decision-making process during the recovery phase of a settlement as well as be the basis for its monitoring over time. Finally, these models can contribute to the estimation of the reconstruction cost of the buildings.

Assigning the macroseismic vulnerability classes to strengthened ordinary masonry buildings: An update from extensive data of the 2016 Central Italy earthquake

Damage scenarios caused by the 2016 Central Italy earthquake confirmed the relevant role of interventions on masonry buildings’ seismic performance, also by increasing (rather than reducing) their vulnerability. Notwithstanding, current literature procedures aimed at assigning to buildings an European Macroseismic Scale 1998 (EMS-98) vulnerability class (A to F) do not consider such influence especially referring to the several intervention techniques applied to masonry buildings since the 1980s in Italy. This impaired a proper matching of vulnerability classes to the real performances, as strengthened buildings are conventionally assigned to average vulnerability conditions (class C).In the present work, vulnerability classes are appropriately assigned to buildings in strengthened conditions, basing on the analysis of 2264 dwellings placed in 19 settlements. Inspections were carried out with a purposely developed rapid visual screening procedure.A performance-based definition of structural types considered a building's masonry quality, diaphragms' stiffness, and kind of interventions graded between downgrading and upgrading. Types with the same behaviour were grouped into vulnerability classes, in the full range from A to D, through a literature model compatible with the EMS-98. Rubble stone buildings with downgrading or worsening interventions behaved like those in original conditions (class A), whereas improved buildings typically performed like class C. Upgrading interventions led to class D, similarly to modern clay block buildings. Masonry quality influenced the classification more than diaphragms' stiffness. The empirical membership of each type to vulnerability classes was obtained, that which allowed to include variously strengthened masonry buildings within the EMS-98 framework.

Inhomogeneity of Macroseismic Intensities in Italy and Consequences for Macroseismic Magnitude Estimation

AbstractWe show that macroseismic intensities assessed in Italy in the last decade are not homogeneous with those of the previous periods. This is partly related to the recent adoption of the European Macroseismic Scale (EMS) in place of the Mercalli–Cancani–Sieberg (MCS) scale used up to about one decade ago. The underestimation of EMS with respect to MCS is about a half of a degree on average and, even more significant, if the MCS intensities are estimated according to the approach developed for the quick evaluations of damage by macroseismic seismologists of the Italian Department of Civil Protection. We also show the inhomogeneity over time of the average differences between instrumental and macroseismic magnitudes computed from intensity data, indicating an average overestimation of magnitudes of about 0.3 units for the instrumental ones before year 1960 and of about 0.2 units for the macroseismic ones after such date. This is consistent with previous studies that hypothesized the incorrect calibration of mechanical recording seismometers operating in Italy and in the surrounding countries before the introduction of the standard electromagnetic seismometers from the beginning of 1960s. For such reasons, the magnitudes of preinstrumental earthquakes in the Catalogo Parametrico dei Terremoti Italiani seismic catalog, used for the most recent seismic hazard assessment in Italy, might be overestimated, on average, by about 0.1–0.2 magnitude units.

The heuristic vulnerability model: fragility curves for masonry buildings

In the framework of seismic risk analyses at large scale, among the available methods for the vulnerability assessment the empirical and expert elicitation based ones still represent one of most widely used options. In fact, despite some drawbacks, they benefit of a direct correlation to the actual seismic behaviour of buildings and they are easy to handle also on huge stocks of buildings. Within this context, the paper illustrates a macroseismic vulnerability model for unreinforced masonry existing buildings that starts from the original proposal of Lagomarsino and Giovinazzi (Bull Earthquake Eng 4(4):445–463, 2006) and has further developed in recent years. The method may be classified as heuristic, in the sense that: (a) it is based on the expertise that is implicit in the European Macroseismic Scale (EMS98), with fuzzy assumptions on the binomial damage distribution; (b) it is calibrated on the observed damage in Italy, available in the database Da.D.O. developed by the Italian Department of Civil Protection (DPC). This approach guarantees a fairly well fitting with actual damage but, at the same time, ensures physically consistent results for both low and high values of the seismic intensity (for which observed data are incomplete or lacking). Moreover, the method provides a coherent distribution between the different damage levels. The valuable data in Da.D.O. allowed significant improvements of the method than its original version. The model has been recently applied in the context of ReLUIS project, funded by the DPC to support the development of Italian Risk Maps. To this aim, the vulnerability model has been applied for deriving fragility curves. This step requires to introduce a correlation law between the Macroseismic Intensity (adopted for the calibration of the model from a wide set of real damage data) and the Peak Ground Acceleration (at present, one of most used instrumental intensity measures); this conversion further increases the potential of the macroseismic method. As presented in the paper, the first applications of the model have produced plausible and consistent results at national scale, both in terms of damage scenarios and total risk (economic loss, consequences to people).