Regional and national seismic hazard models used in probabilistic seismic risk analysis often rely on generalized proxy‐based site terms to account for ground shaking amplification. This can result in coarse representations of site response, which can introduce bias or additional uncertainty in the associated risk results. While some studies have explored alternative techniques to characterize site response in seismic hazard and risk analysis, these have typically been applied within deterministic frameworks or with a focus on specific localities. This study presents a comprehensive evaluation of methods for incorporating site effects in PSRA across five cities with varying seismic hazard, exposure, and soil conditions. By comparing 17 distinct site effects approaches, we evaluate how different proxies and methodologies affect seismic risk metrics. The findings are used to provide a set of recommendations aimed at enhancing the reliability and accuracy of seismic risk assessments.

The 2020 Mw 6.4 Petrinja earthquake in central Croatia is one of the European strongest continental earthquakes in recent decades. This event shed light on the poorly investigated Petrinja-Pokupsko Fault (PPKF) zone, a right-lateral fault system accommodating a fraction of the shortening between the Adria and European plates. Through field observations and high-resolution Lidar-derived digital elevation models of the central section of the PPKF, we precisely mapped the fault trace, revealing a discontinuous geometry with a main fault strand and left-stepping segments in agreement with the position of the 2020 surface ruptures. To the north, the accumulated relief from this transpressive fault system decreases, and the fault trace becomes less distinct, suggesting a northward propagation of the deformation. Cumulative offsets of 4 to 24 meters along the main fault strands in the central and southern sections of the fault attest to its Quaternary activity. Dating results suggest offset markers at the Marine Isotopic Stage 4 (MIS 4), the Late Glacial Maximum (LGM) or the Early Holocene periods, allowing for the first direct estimation of the fault slip rates. Preliminary estimates indicate that, assuming a common MIS 4 or LGM age for the investigated markers, fault slip rates range from 0.2 to 0.7 mm/yr and 0.7 to 1.6 mm/yr, respectively. In contrast, assigning Early Holocene ages would imply much higher - and likely unrealistic - slip rates of 1.6 to 3.9 mm/yr. Although the estimated loading rates vary greatly and depend on strong assumptions regarding the age of the markers abandonment, our results suggest a minimum fault slip-rate of 0.2 mm/yr for local seismic hazard assessments.

Abstract. Earthquake surface ruptures are a significant hazard for critical infrastructure and society. Probabilistic Fault Displacement Hazard Analysis (PFDHA) uses empirical and numerical models to estimate the surface rupture likelihood as the first component. However, empirical datasets are often incomplete and limited to few geodynamic settings, reducing their accuracy for site-specific analyses. Moreover, existing models do not capture the influence of physical fault parameters, such as geometry, on surface rupture occurrence nor its spatial variability. We use the RSQSim rate-and-state earthquake simulator to simulate seismicity across twelve alternative geometries of a test fault that incorporate variations of fault connectivity at depth, dip and fault trace sinuosity, aiming for a systematic evaluation of their influence on the probability of primary surface rupture and its spatial variability. Our results show that fault geometry is key in controlling the probability of surface rupture. Models with fault connectivity at depth and greater fault trace sinuosity yield higher probabilities than their counterparts. Conversely, disconnected models limit rupture propagation across segments, reducing surface rupture capability in specific fault regions. This study demonstrates the importance of considering fault geometry when assessing seismic hazards and confirms that earthquake cycle simulators offer a robust tool for next generation PFDHA models.

The use of physics-based earthquake simulators is increasingly common in earthquake forecasting for seismic hazard. Their popularity is related to their ability to overcome completeness limitations of real seismicity catalogues, while reproducing complex earthquake rupture behavior and interaction patterns through the modelling of the physical processes involved in earthquake nucleation and rupture propagation. One common challenge when designing earthquake simulations is the selection of the input parameters that will produce the most feasible models in terms resemblance to natural earthquake processes and relationships, e.g., the rate-and-state frictional parameters – a, b – and the initial normal stress. The frequent lack of empirical data on such parameters, often bases their selection on non-systematic testing and qualitative model performance analysis, thus potentially reducing the objectivity of the modelling. We present a new quantitative approach to evaluate and rank the performance of multiple earthquake simulation models based on a workflow that scores each synthetic catalog according to their combined fit to objective seismological benchmarks. These benchmarks rely on widely used empirical earthquake data: 1) scaling relationships, 2) shape of the magnitude-frequency distribution and 3) rates of surface ruptures from paleoseismology. The approach permits an objective and effective approximation to model performance evaluation, allowing to easily identify which models (and input parameter combinations) simulate better natural earthquake relations and behavior. The algorithm-based approach also facilitates the exhaustive analysis of many input parameter combinations and allows the identification of systematic correlations between parameters and model performance. We validate the approach with earthquake simulations on a theoretical planar fault and with published simulations at the Eastern Betics Shear Zone (EBSZ) in southeastern Spain. In both cases, the method successfully ranks the models with better resemblance to natural catalogues, while avoiding self-correlation of the benchmark scores, i.e., the best model is not the best in all benchmarks but the better balanced across them. In the case of the EBSZ, our ranking analysis replicates the qualitative and manual analyses previously published, which reinforces the usefulness of the approach. We also identify very clear correlations between the model performance and the rate-and-state a and b parameters. In particular, we observe that larger differences between a and b tend to better model performance. Conversely, the initial normal stress does not correlate with the performance. Overall, we estimate that the approach can ease researchers on earthquake simulation design and building, and on better understanding the impact of selected input parameters into the physics-based models. Moreover, the model ranking results can be employed to drive further analysis such as weighting of earthquake forecast models in seismic hazard logic trees.

In many countries, the acceptance of a new National Seismic Hazard Model (NSHM) to be used in risk reduction strategies usually comes after a deep scrutiny and analysis of the differences with the previous NSHM, in terms of their scientific reliability and of the practical applicability for building code purposes. These two requirements are fully legitimate, but they are conceptually very different and often mixed up in the scientific and public discussion. Although we acknowledge that any use of an NSHM in terms of risk reduction strategies ought to consider many additional nonscientific challenges, we claim that NSHM is a scientific model; hence, its credibility is intimately and exclusively related to its scientific reliability. Stimulated by how the last NSHM in Italy has been evaluated, in this article, we discuss in detail how to test the reliability of an NSHM with the available data, and the meaning of comparing the outcomes of the new and old NSHMs. Finally, we propose recommendations that may guide any scientists to navigate across the tumultuous process of assessing the scientific reliability of an NSHM and comparing, meaningfully, the outcomes of different NSHMs.

Probabilistic Fault Displacement Hazard Analysis (PFDHA) is pivotal in assessing the probability of surface fault displacement during seismic events, with critical implications for infrastructure systems like pipelines and lifelines. Recent earthquakes have underscored the importance of fault displacement as a cause of damage. This study aims to improve predictive models and regression analyses to assess the probability and expected amount of throw on distributed ruptures (DR) from normal and reverse earthquakes. The research leverages the SURE 2.0 database, which classifies ruptures into different ranks, including primary and various typologies of distributed ruptures. Logistic regression models are employed to assess the probability of DR occurrence, considering factors such as earthquake magnitude, proximity to the principal fault, faulting style, and DR location (hanging wall/footwall) as predictor variable. In addition, a fault displacement model is formulated to estimate the median throw on DRs based on these parameters and on a mean throw on the principal fault. The outcomes offer valuable insights into the characteristics and likelihood of DRs, carrying implications for PFDHA applications. The study introduces a decision-tree algorithm designed to assist PFDHA practitioners in selecting the most suitable approach based on the available geological knowledge. This study contributes to an improved understanding of fault displacement hazard analysis and provides a versatile framework for its application across diverse geological contexts.

The Mw 7.0 Avezzano earthquake in the Abruzzo region of Italy claimed similar to 33,000 lives on January 13, 1915 making it one of the worst disasters in modern Italian history. The main rupture occurred along the Venere Fault, characterized by a polished, locally shiny, or powdery fault mirror showing extensive downdip striations, slickensides, and local reddish iron-oxide/hydroxide stains. The layer immediately below the mirror is a carbonate ultracataclasite that locally grades into an unconsolidated carbonate gouge. This type of carbonate fault mirror typically forms through two distinct synkinematic processes: i) intense frictional heating causing decarbonation, or ii) progressive grain-size reduction during slip at seismic velocities. In either case, friction drops substantially after initial displacement. The first process also results in intense fault pressurization followed by subsequent drastic drop in normal stress. Despite recent advances, the switch from high-friction/low slip velocity to low-friction/high slip velocity conditions in carbonate is still not fully understood. The Venere Fault, characterized by proven friction at seismic slip velocity, provides an ideal setting to investigate the nature and extent of dynamic weakening processes in carbonate faults. We use the high temperature sensitivity of iron oxide/hydroxide assemblages, and their magnetic remanence, to estimate frictional heat. Evidence for seismic slip in iron oxides and temperature uniformity along the fault surface have been tested through demagnetization experiments and 1D heat conduction modeling. Our data shows that the fault mirror underwent frictional heating during the 0.8 m slip event, but that this displacement was insufficient to reach pervasive decarbonation. We constrain the peak coseismic temperature along the fault plane to <400 degrees C through demagnetization experiments and 1D heat conduction modeling. Our results emphasize that coseismic deformation along natural faults is complex and therefore requires complementary field observations at multiple scales in order to encompass a broad range of faulting processes.

Physics-based earthquake simulators are an increasingly popular modeling tool in earthquake forecasting for seismic hazard as well as fault rupture behavior studies. Their popularity comes from their ability to overcome completeness limitations of real catalogs, and also because they allow reproducing complex fault rupture and interaction patterns via modeling the physical processes involved in earthquake nucleation and propagation. One important challenge of these models revolves around selecting the physical input parameters that will yield the better similarity to earthquake relationships observed in nature, for instance, the frictional parameters of the rate-andstate law-a and b-or the initial normal and shear stresses. Because of the scarcity of empirical data, such input parameters are often selected by trial-error exploration and predominantly manual model performance analyses, which can overall be time consuming. We present a new benchmarking approach to analyze and rank the relative performance of simultaneous earthquake simulation catalogs by quantitatively scoring their combined fit to three reference function types: (1) earthquake-scaling relationships, (2) the shape of the magnitude-frequency distributions, and (3) the rates of the surface ruptures from paleoseismology or paleoearthquake occurrences. The approach provides an effective and potentially more efficient approximation to easily identify the models and input parameter combinations that fit more closely to earthquake relations and behavior. The approach also facilitates the exhaustive analysis of many input parameter combinations, identifying systematic correlations between parameters and model outputs that can potentially improve the overall understanding of the physics-based models. Finally, we demonstrate how the method results agree with the published findings in other earthquake simulation evaluations, a fact that reinforces its overall usefulness. The model ranking outputs can be useful for subsequent analyses, particularly in seismic hazard applications, such as the selection of appropriate earthquake occurrence rate models and their weighting for a logic tree.

This study presents a numerical approach for probabilistic fault displacement hazard analysis (PFDHA), aimed at addressing an alternative solution to commonly used empirical methodologies. Our model utilizes probability distributions to compute the conditional probability of surface rupture (CPSR). Leveraging earthquake catalogs, we derived the hypocentral depth distribution (HDD) across eight globally distributed seismotectonic regions categorized by faulting kinematics (normal, reverse, strike-slip). We calculated the hypocentral depth ratio (HDR) distribution, to model rupture position from the hypocenter. Rupture widths are estimated as a function of magnitude based on previously published scaling relations. User-input parameters, including fault style, average dip angle, and seismogenic depth, with associated uncertainties, derive the CPSR estimation of surface rupture occurrences. Our findings highlight seismogenic depth as the most influential parameter and reveal correspondences between empirical curves derived for specific regions. These findings support the use of source-specific surface rupture probability assessments over approaches based on global datasets, and underscore the importance of considering the local seismotectonic setting when evaluating fault displacement hazard. The numerical code for CPSR calculation has been developed and is openly accessible on GitHub.

We present a Probabilistic Fault Displacement Hazard Analysis (PFDHA) for a strategic dam located in the Upper Tiber Valley (Northern Apennines of Italy) claimed to be sited on a supposed capable fault (Montedoglio fault). We verify the seismic capability of the Montedoglio fault through detailed geological and geophysical analyses. We find no evidence for considering the Montedoglio fault as an active and capable structure, the fault being constituted by a system of discontinuous parallel faults, apparently inactive since more than 56 +/- 3 ka, and likely unable to nucleate strong surface rupturing earthquakes. Since the dam lies on the hanging wall of the closest major active fault of the area (Anghiari normal fault, similar to 1.5 km away), we investigate the likelihood of having distributed faulting at the dam's site in case of a strong surface-rupturing earthquake occurring on the Anghiari fault. We apply a probabilistic approach to obtain hazard curves of exceedance of vertical displacement at the dam's site for different rupture scenarios. We show that the mean hazard curve is always below an annual frequency of exceedance of 1 x 10(-5), corresponding to displacement values below 1 cm over 100,000 years of return period. The study highlights several weaknesses and uncertainties in using PFDHA with state-of-the-art models, suggesting the need for improvements to enhance their applicability in earthquake engineering geology practice.

A key challenge in paleoseismology is constraining the timing and occurrence of past earthquakes to create an earthquake history along faults that can be used for testing or building fault-based seismic hazard assessments. We present a new methodological approach and accompanying code (Paleoseismic EArthquake CHronologies, PEACH) to meet this challenge. By using the integration of multi-site paleoseismic records through probabilistic modeling of the event times and an unconditioned correlation, PEACH improves the objectivity of constraining paleoearthquake chronologies along faults, including highly populated records and poorly dated events. Our approach reduces uncertainties in event times and allows increased resolution of the trench records. By extension, the approach can potentially reduce the uncertainties in the estimation of parameters for seismic hazard assessment such as earthquake recurrence times and coefficient of variation. We test and discuss this methodology in two well-studied cases: the Paganica Fault in Italy and the Wasatch Fault in the United States.

Fault displacement can be a source of hazard for critical infrastructures located in the nearby of a capable fault. This issue is usually addressed with zonation and avoidance strategies, but sometime the facilities have not this option. An alternative approach to assess likelihood of exceeding a certain level of displacement for pre-existing infrastructures is the Probabilistic Fault Displacement Hazard Analysis. Different empirical approaches have been proposed since the early 2000s to assess the probability of occurrence and the probability of exceedance of certain values of displacement, for both Primary and Distributed faulting, starting from the fault parameters. We propose the methodological approach used to gain the needed parameters and the results of the PFDHA applied to the Anghiari Fault, a poorly constrained NE-dipping segmented normal fault located in the Upper Tiber Valley (Italy) and belonging to the well-known Altotiberina low-angle normal fault system.In order to constrain the fault geometry and to select sites suitable for paleoseismologic trenching we performed geological survey, morphotectonic analysis and geophysical investigations. To assess the capability of the fault and its rate of activity we carried out a paleoseimic campaign, investigating several segments of the Anghiari fault. To obtain a multiscale evaluation of the fault slip rate, we collected samples to date paleosurfaces displaced by the fault with the cosmogenic nuclides methodology. At the end we performed the PFDHA obtaining curves and maps of hazard for both primary and distributed faulting, managing the uncertainties through various rupture scenario involving different fault segment.

This repository contains the datasets and codes supplementary to the article "A multi-benchmark performance analysis of physics-based earthquake simulations" submitted to Geophysical Research Letters. The datasets include the codes to run the ranking analyses, inputs and outputs for the RSQSim earthquake simulation cases explained in the paper: a single fault and the fault system of the Eastern Betics Shear Zone (simulations from Herrero-Barbero et al. 2021). The results and data are stored in a separate folder for each case study presented in the paper: "Single fault" and "EBSZ". Each folder contains a series of subfolders and a Python script to run the ranking analysis for that specific case study. The script contains the default path references to read all necessary input files for the analysis and automatically save all the outputs. The subfolders are: ./Inputs: This folder contains the input files required for the RSQSim simulations. This includes: a. The fault model ("Nodes_RSQSim.flt" and "EBSZ_model.csv" for the single fault and EBSZ cases, respectively), which specifies the coordinate nodes of the fault triangular meshes and fault properties such as rake (º) and slip rate (m/yr). b. Neighbor file ("neighbors.dat"/"neighbors.12") that contains lists of triangular patches of the fault model that are neighboring. This file is used in RSQSim. c. Input parameter file ("Input_Parameters.txt"): this file specifies the parameters that are variable in each catalogue. This file is just for information purposes and is not used for the calculations. d. Parameter file(s) to run the RSQSim calculations. *For the single fault, this file is common ("test_normal.in") and is updated during the calculation when executing the "Run.sh" file in the terminal when running RSQSim. This file contains a script that loops through the input parameters a, b and normal stress explored in the study and changes the input parameter file accordingly in each iteration. *For the EBSZ, this file is specific for each simulation ("param_EBSZ_(n).in"), as each simulation was run separately. e. (Only for the EBSZ case) Input paleoseismic data for the paleorate benchmark. One file ("coord_sites_EBSZ.csv") contains a list of UTM coordinates of each paleoseismic site in the EBSZ and another ("paleo_rates_EBSZ.csv") contains the mean recurrence intervals and annual paleoearthquake rates in those sites (data from Herrero-Barbero et al., 2021). ./Simulation_models: contains several subfolders, one for each simulated catalogue (96 for the single fault case and 11 for the EBSZ). Each subfolder contains data that is read by the ranking code to perform the analysis. *For the single fault, the folder names follow the structure "model_(normal stress)(a)(b)". *For the EBSZ, the folder names are "cat-(n)". ./Ranking_results: contains the outputs of the ranking analysis, which are two figures and one text file. *Figure 1 ("Final_ranking.pdf"): visualization of the final ranking analysis for all models against the analyzed benchmarks. *Figure 2 ("Parameter_sensitivity.pdf"): visualization of the final and benchmark performance versus the input parameter of the models. *Text file ("Ranking_results.txt"): contains the final and benchmark scores of each simulation model. This file is outputted so the user can reproduce and customize their own figures with the ranking results. To use the ranking codes in you own datasets, please replicate the folder structure explained above. Use the code that best suits your data: use the one for the single fault if you wish not to use the paleorate benchmarks, and use the EBSZ one if you wish to include these data in your analysis. At the beginning of the respective codes (before the "Start" block comment) you will find the variables where the file names of the fault model and paleoseismic data are indicated. Change them to adapt it to your data. There you can also assign weights to the respective benchmarks in the analysis (default is set at equal weight for all benchmarks). For updates of the code please visit our GitHub: https://github.com/octavigomez/Ranking-physics-based-EQ-simulations

Europe has experienced over the last years earthquakes of moderate magnitude (Mw 5-6), yet destructive, reminding us of the seismogenic potential of slowly deforming regions. Among them, the 2020 Mw 6.4 Petrinja earthquake ruptured the Petrinja-Pokupsko Fault (PPKF) in Central Croatia, about 50-km southeast of Zagreb, a region in which the caracterisation of seismogenic faults had been insufficiently studied before that event. Understanding the strain accommodation through time and space is critical for accurate assessment of the regional seismic hazard.Using field observations and high-resolution topographical data derived from airborne LiDAR (~10 cm resolution) and tri-stereo satellite images (Pléiades, resolution 50 cm), we accurately mapped the fault trace, underlined at several sites by geomorphic markers such as valleys, terrace risers, and alluvial fans that have recorded cumulative displacements ranging from 5 to > 50 m and potentially up to ~180 m. Along the studied section, our fault mapping is composed of a clear NW-SE-trending 10-km-long strand between Donja and Cepelis, and of 1-4-km-long right-stepping segments marked by a non-negligible vertical component. The southern strand is composed of 2-3 sub-parallel segments that accommodate the deformation within a < 500 m wide fault zone.We have identified several sites on the main southern strand where offsets have been accurately measured and where displaced markers have been sampled for cosmogenic nuclide exposure dating and radiocarbon datings. This will allow to estimate the slip-rate for this fault at different sites and over several time spans.The mapped fault appears very discontinuous with the deformation absorbed by a series of small fault sections rather than on a single fault strand. This likely reflects a recent transpressive deformation, with immature faults, in agreement with the source parameter of the 2020 Petrinja earthquake derived from seismology.Finaly, the 2020 coseismic surface ruptures affected the northern section of the PPKF, while the mapped cumulative displacements appears more prominent along the southern section. A better knowledge of the seismic history of this entire fault system is thus crucial for seismic hazard assessment of this area.

&lt;p&gt;TREAD is a new project funded by the European Commission in the framework of Marie Sklodowska-Curie actions, Horizon Europe Doctoral Networks.&lt;/p&gt;&lt;p&gt;The aim of TREAD is to train a new generation of researchers to tackle the challenges of earthquake forecasting in complex tectonic settings using integrated observations and physics. The TREAD objectives are: (i) to develop a novel integrative approach to seismic hazard analysis in Europe and the Mediterranean from small-scale laboratory experiments to large-scale observations. (ii) to establish physics-based earthquake modelling bridging time scales from millions of years to fractions of a second in complex tectonic settings. (iii) to improve the link between earthquake geology, computational modelling and hazard and risk assessment with a focus on the needs of governments, industry and scientific stakeholders.&lt;/p&gt;&lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;p&gt;To reach these objectives the TREAD consortium comprises 14 academic and 8 non-academic institutions, of which 8 private partners, of high scientific level, from 7 European countries, covering cutting-edge knowledge and expertise in observational, experimental and modelling fields. 11 PhD positions will be available soon.&lt;/p&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt;

&lt;p&gt;A major challenge in seismic hazard research is to quantify the frequency of large earthquakes along active faults, more so when the observational time windows of seismic catalogs are much shorter than the average fault recurrence intervals. In this respect, paleoseismology continues to prove to be an excellent tool to extend the seismic catalogs of faults into prehistorical times. The combination of the ever more advanced trenching surveys and accurate numerical dating techniques allows constraining the timing of paleoearthquakes and, for some datasets, approximating their recurrence models. Despite this, paleoseismic data carries along large uncertainties frequently related to dating technique limitations, poor stratigraphic preservation, and along-strike slip variability that hinder the identification of a complete paleoearthquake record. Subsequently, these issues, among others, challenge the constraint of reliable earthquake chronologies along faults and of the parameters defining their earthquake cycle.&lt;/p&gt; &lt;p&gt;We present an automatic workflow capable to compute and constrain earthquake chronologies along a fault based on the correlation of its available paleoseismic records, including multi-site and poorly constrained datasets. Our inherent premise is that the correlation of paleoseismic data from multiple along-fault locations can help to improve the time constraints and completeness of its paleoearthquake record. Given that paleoseismic records are, by definition, underpopulated, event correlation is not restricted to single occurrences. Instead, an event in a site might be simultaneously correlated with more than one in another if time compatible. Furthermore, to avoid subjectivity biases in event timing estimates and correlation, we exclusively rely on the trench numerical dates limiting each event horizon as the inputs. All earthquake chronologies are modelled probabilistically with a four-step algorithm as we detail. First, all earthquake times in each site are computed as probability density functions (PDFs) using the input numerical dates. The event PDFs from all sites are then integrated to derive a mean curve representing the overall event probabilities for the studied fault in the time span investigated. The probability peaks in this curve, which are assumed as indicative of the event timing at the fault scale, are automatically detected based on peak prominence analysis. A final PDF is then computed for each peak by multiplying all site event PDFs intersecting the peak position. The set of product PDFs constitutes the earthquake chronology of the fault, provided to the user in simple output files that can be externally used to calculate fault parameters for the seismic hazard assessment, and to visualize the modelling.&lt;/p&gt; &lt;p&gt;Preliminary tests on several paleoseismic datasets of the Central Apennines (Italy), the Eastern Betics (Spain), the Dead Sea Fault and the Wasatch Fault (US), have provided good outcomes. The approach significantly reduces the uncertainties in event timing of paleoearthquakes and provides an objective and reliable interpretation of the datasets, especially when these are complex or have wide uncertainties. By extension, the workflow has the potential to reduce the uncertainties in earthquake recurrence estimates and can give insight on the recurrence models that better describe the earthquake cycle in the studied faults.&lt;/p&gt;

A board game designed by psychologists and geologists to improve seismic-risk perception is presented. In a within-subjects repeated-measure study, 64 Italian high-school students rated their perception of seismic risk in relation to the hazard, vulnerability and exposure of the area in which they lived, before and after the game. A repeated-measures analysis of variance (ANOVA), which considered perception of seismic risk as the dependent variable and time as the independent variable, revealed that the board game affected the dependent variable, particularly the perception of hazard and vulnerability. The results confirm the effectiveness of the game in changing participants’ seismic risk perception, properly because the game was built with consideration of the variables that make up seismic risk. The board game proved to be an effective and fun educational tool to be used in future earthquake risk prevention programs.

A new probabilistic seismic hazard model, called Modello di Pericolosità Sismica 2019 (MPS19), has been recently proposed for the Italian territory, as a result of the efforts of a large national scientific community. This model is based on 11 groups of earthquake rupture forecast inputs and, particularly, on 5 area-source seismogenic models, including the so-called MA4 model. Data-driven procedures were followed in MA4 to evaluate seismogenic parameters of each area source, such as upper and lower seismogenic depths, hypocentral-depth distributions, and nodal planes. In a few cases, expert judgement or ad hoc assumptions were necessary due to the scarcity of data. MA4 consists of 20 seismicity models that consider epistemic uncertainty in the estimations of the completeness periods of the earthquake catalogue, of maximum magnitude values and of seismicity rates. In particular, five approaches were adopted to calculate the rates, in the form of the truncated Gutenberg–Richter frequency–magnitude distribution. The first approach estimated seismicity rates using earthquakes located in each area source, while the other approaches firstly calculated the seismicity rates for groups of areas considered tectonically homogeneous and successively partitioned in different ways the values to the area forming each group. The results obtained in terms of seismic hazard estimates highlight that the uncertainty explored by the 20 seismicity models of MA4 is at least of the same order of magnitude as the uncertainty due to alternative ground motion models.

During the new elaboration of the hazard model for Italy, a study on the indications we may collect concerning the tectonic style of future earthquakes and seismic ruptures has been done. All available seismic moment tensors for relevant seismic events (Mw starting from 4.5) of the last 100 yrs, first arrival focal mechanisms for less recent earthquakes and geological data on activated faults have been collected in a unique database, that includes thousands of data all over the Italian peninsula. After several summation trials, changing parameters, seismogenic thicknesses and taking into account the characteristics of seismicity distribution, a unique computation procedure has been applied to each of the 50 seismic zones of the new seismogenic zoning for Italy. The results for several seismic zones are very stable, for instance, in the southern Apennines we expect mostly extensional earthquakes, although in the outer part of the chain strike-slip events are possible. In the northern part of the Apennines, we also expect different, opposite tectonic styles for different hypocentral depths. In several zones characterised by a low seismic moment release, the next possible tectonic style of future earthquakes is less clear and it has been represented using different combination (total or partial) of random sources. A comparison of our results with recent earthquake moment tensors show a good agreement with the computed possible tectonic style.

In the Central Apennines (Italy), up to now, no absolute dating directly based on the moraines has been carried out to constrain glacial oscillation. However, climatic constrains are often used in the Central Apennine to estimate long term (> 10 ka) fault slip rate. In addition slip rate assessments based on offset morphotectonic markers on the main branches of fault systems and encompassing several seismic cycles (> 10 ka) are sparse. This is particularly true for the Monte Vettore-Monte Bove fault system which triggered the 2016-2017 seismic sequence. We thus provide new assessment for the vertical slip rates along the Mt Vettore-Mt Bove fault system. Offset measurements were made using a 5-cm resolution DEM obtained through a drone survey and constrain a fault scarp height of 15.5 ± 1.4 m and a cumulative offset of 32-40.5 m. Samples were collected from the Valle Lunga terminal moraine at 1710 m asl and yield 36Cl exposure ages of 12.7 + 2.2/-1.9 ka while the flat, abraded surface located on top of the tectonic scarp yield 36Cl exposure ages of 23.4 + 5.3/-4.3 ka. Assuming the offset started to accumulate when climate conditions allow its preservation, thus once the surface was abandoned, we constrain a vertical slip rate of 1.2 ± 0.2 mm/yr along the master branch of the Mt Vettore normal fault. This rate is higher than the ones previously obtained from trenches along secondary splays of the Mt Vettore-Mt Bove and on the Norcia fault systems. Besides, the yielded chronology for the last glacial maximum in that area at ~23 ka is in good agreement with the timing previously proposed for the LGM in the Apennines.