The Neo-Deterministic Seismic Hazard Assessment (NDSHA) has been applied for nearly three decades to evaluate seismic hazard at both regional and local scales in Italy and internationally. At the local scale, NDSHA is able to integrate geological, seismotectonic, and geotechnical data to generate ground motion scenarios, broadband time histories, and related damage indicators, which serve as input for engineering design. Furthermore, NDSHA is a comprehensive approach to assess the local seismic response (LSR) to be used in microzonation studies. Hereinafter, the NDSHA-based analysis of LSR along a 2D section at the Chieti site (Italy) will be illustrated. While results are broadly consistent with traditional 2D finite element method, NDSHA offers additional insight into subsurface wave field behavior within the simulated domain.

A new application of the Neo-Deterministic Seismic Hazard Assessment (NDSHA) to free field seismic hazard at the site is illustrated. This physics-based scenario approach is used to assess the seismic response at Chieti's city center (Abruzzo, Italy) along a laterally varying representative section. The results are compared with those obtained through the AlgoShake2D Finite Element Method (from now on simply FEM) in the same section. Both methods employ a viscous-elastic rock and soil dynamic behavior. In addition, non-linear analyses are performed with FEM method. NDSHA models the directivity and the dispersion due to the medium anelasticity along the propagation path of P and S seismic waves incoming from the bedrock of the section, while FEM uses the popular but very simplified assumption of vertical upward propagation to the surface of only SH waves. FEM implements the equivalent linear approach to simulate the non-linear behavior of soil material under seismic wave solicitations. In Chieti's case study, both FEM and NDSHA results underline how much the stratigraphy contributes to the distortion (amplification/reduction) of the propagating perturbation compared to the reference regional average propagation (1D), as opposed to the topography. FEM acceleration response spectra (both viscous-elastic and equivalent-linear) are naturally enveloped by NDSHA 95% percentile spectrum although the median spectrum and the FEM mean spectrum show similar shapes. The NDSHA amplification functions are larger than the FEM ones, especially for periods lower than 0.5 s. This result can be attributed to the too-simplistic body wave propagation simulated by the FEM approach. The most amplified zone is located at the foothill and the amplification is 3.5 on average below 0.5 s. Although both methods predict a secondary role of the topographic effect, the NDSHA causal signals that consider the directivity of the wavefield, its complex refraction within the propagation medium (Chieti's vertical section), and some possible complexities of the earthquake source indicate that higher amplifications than FEM's ones should be accounted for when more realistic simulations are available. Based on the precautionary principle, given the complexity of real earthquakes, it is therefore natural to recommend the routine use of NDSHA.

Neo-Deterministic Seismic Hazard Assessment (NDSHA), dating back to the turn of the Millennium, is the new multi-disciplinary scenario- and physics-based approach for the evaluation of seismic hazard and safety–guaranteeing “prevention rather than cure.” When earthquakes occur, shaking certainly does not depend on sporadic occurrences within the study area, nor on anti-seismic (earthquake-resistant) design parameters scaled otherwise to probabilistic models of earthquake return-period and likelihood — as adopted in the widespread application of the model-driven Probabilistic Seismic Hazard Analysis (PSHA). Therefore, from a policy perspective of prevention, coherent and compatible with the most advanced theories in Earth Science, it is essential that at least the infrastructure installations and public structures are designed so as to resist future strong earthquakes. Evidences and case histories detailed in the newly published book Earthquakes and Sustainable Infrastructure present a new paradigm for Reliable Seismic Hazard Assessment (RSHA) and seismic safety — comprehensively detailing in one volume the ‘state-of-the-art’ scientific knowledge on earthquakes and their related seismic risks, and actions that can be taken to ensure greater safety and sustainability. The book is appropriately dedicated to the centenary of Russian geophysicist Vladimir Keilis-Borok (1921–2013), whose mathematical-geophysical insights have been seminal for the innovative paradigm of Neo-deterministic seismic hazard assessment. This review focuses on Hazards, Risks and Prediction initially discussed in the introductory Chapter 1 — an understanding of which is essential in the applications of the state-of-the-art knowledge presented in the book’s 29 following chapters.

For relevant engineering purposes a viable reliable alternative to standard estimates of seismic hazard is represented by the use of scenario earthquakes, characterized not only in terms of magnitude, distance and faulting style, but also taking into account the complexity of the kinematic source rupturing process. Multi-scenario-based NDSHA (Neo-Deterministic Seismic Hazard Assessment) effectively accounts for the tensor nature of earthquake ground motions, formally described as the tensor product of the earthquake source functions and the Green’s functions of the transmitting anelastic medium, naturally supplying realistic time series, readily applicable to engineering analysis. Furthermore, it does not rely on scalar empirical ground motion attenuation models (GMPEs), as these are often both weakly constrained by available observations and fundamentally unable to account for the tensor nature of earthquake ground motions. This methodology has been successfully applied to many urban areas worldwide for the purpose of seismic microzoning, to strategic buildings, lifelines and cultural heritage sites. Some examples for selected sites in Central Italy, affected by the seismic sequence started in 2016, are here discussed, analyzing the energy content of the synthetic strong motion time histories, including the ones that predicted the spectral characteristics of the ground shaking due to the 24 August 2016 event. Specifically, the energy content obtained from (1) linearly scaled real records, (2) spectral matched records, (3) artificial accelerograms and (4) physics-based NDSHA ground motions, selected for a bridge hypothetically located at Amatrice, is compared. The comparison shows that the generation of artificial accelerograms (3) and partially also the spectral matching process (2) are characterized by an increase of the ground motion energy parameters with respect to the physics-based synthetic signals (4) and the linearly scaled records (1).

An application of a physics-based approach to the seismic site response analyses has been undertaken at Chieti city center using the Neo-deterministic Seismic hazard assessment (NDSHA). This method combines the realistic numerical simulation of the source rupture mechanism and the-wave propagation from the earthquake source to the free surface at the investigated site. Although NDSHA simulates the soil behavior as a viscous elastic material thus not considering the possible non-linear behavior at a large deformation level, it enables accounting for the directivity of the seismic waves. The directivity, as the present study demonstrates, greatly affects the relevance of the topographic effect on the local amplitude increase or decrease of the wave field (seismic amplification or deamplification) depending on the distance of the seismic source to the considered site. Results from this study, located at the Chieti city site, point out that the geo-lithological conditions of Chieti’s hill induce amplifications as large as 3 whereas the topographic effect plays a secondary role due to the incidence angle of the seismic waves generated by the hypocentres located at distances in the range of 24- 42 km from Chieti’s site.

In the network-based on-site earthquake early warning system (EEWS), the 'blind zone', namely the zone where the issued warning arrives later than the destructive S and surface waves, is one of the challenges affecting its effectiveness. The 'blind zone' is determined by the interstation distance, or equivalently the density of seismic stations, of the network. In this paper, we suggest a practical approach according to which, when in a region a temporary increase of seismic hazard is declared, additional stations are deployed in such a way that the blind zone is temporarily reduced. In the procedure, the time-dependent neo-deterministic seismic hazard assessment (TD-NDSHA) plays a vital role in the identification of the regions potentially exposed to high macroseismic intensities. As a showcase example, we consider the scenario of year 2014 at the Sichuan-Yunnan border of southwest China. The TD-NDSHA is based on the standard NDSHA procedure at regional scale (bedrock conditions), with the 'controlling earthquakes' defined on the basis of the Annual Consultation. We show that the 'blind zone' can be reduced in the identified areas of interest (e.g., MMI = VI), by deploying a limited number of additional seismic stations. In the case where false alarms can be tolerated, significant reduction of the 'blind zone' can be implemented by moving from a network- based EEWS to a single-sensor- based EEWS and skipping the process of location and magnitude-determination/prediction procedures.

The neodeterministic seismic hazard assessment (NDSHA), based on the generation of synthetic seismograms from a set of earthquake sources and layered anelastic structural models, has been applied at a regional scale in the Iberian Peninsula. Two seismogenic source models are combined: one of the polygonal zones and a second one using nodes obtained by morphostructural analysis and pattern recognition techniques. Hazard maps of maximum ground displacement, Dmax, maximum ground velocity, Vmax, and design ground acceleration, DGA, are produced with a maximum frequency content of 1 Hz. NDSHA results show the largest Dmax values (class 7–15 cm) in central-western Portugal and similar high Vmax (class 8–15 cm/s) both in the west and in the east of the Iberian Peninsula. DGA reaches its highest values (class 0.15–0.30 g) in central-western Portugal, and in eastern Spain (class 0.08–0.15 g).

For the concept of next-generation Early Earthquake Warning (EEW), the core idea is to combine EEW with seismic hazard assessment. In other words, to perform rapidly the computation of seismic hazard after the occurrence of an earthquake is detected and then to issue accurate warning, including lead time and potential seismic hazard level, to different end-users, e.g., railway system, working nuclear power plants and precision surgery in progress. We propose a scenario-based EEW by using the physics- and scenario-based hazard assessment, well known as Neo-deterministic Seismic Hazard Assessment (NDSHA). NDSHA can reliably compute the physically possible maximum ground motion response, including Maximum Credible Earthquakes (MCEs). In the framework of NDSHA, the general unit of processing time ranges from minutes to seconds, depending on the size of the study area and on the amount of computations. When the structural spectral information is available, the processing time significantly drops to a few seconds. Accordingly, a NDSHA scenario-based EEW relies on a hazard database, made by a collection of Modified Mercalli Intensity (MMI) maps, prepared and stored in advance. The establishment of such a hazard database is to consider all possible earthquake scenarios around target source zones based on now-available geophysical knowledge. Taking Xianshuihe (XSH) fault as an example, the six steps of the procedure to build the necessary hazard database could be the following: (1) definition of seismogenic zone; (2) definition of the first scenario source; (3) determination of source parameters; (4) determination of structural models; (5) computation of synthetic seismograms from the first source; (6) repeat (1) ~ (5), to travel all sources. Steps 1 to 6 allows us to obtain final (3264 in our case) results, i.e., the MMI maps for the adopted earthquake scenarios, which should be well representative of the potential earthquakes related to XSH. As a first-order approximation in the construction of the hazard database, we assigned a characteristic focal mechanism for each cellular scenario earthquake. Once the hazard database is available, effective warning can be quickly issued to different end-users by selecting the suitable MMI map in the hazard database.

Earthquakes cannot be predicted with ultimate precision, so that the progressive reduction of the prediction uncertainty in space and time is an evergreen and challenging task, both from the scientific point of view for the intrinsic complexity of the seismic phenomenon and for its high societal relevance. To this aim, algorithms exist (like CN, M8, and M8S) based on objective recognition of seismicity patterns that have been already tested for some decades for intermediate-term middle-range prediction of strong earthquakes above a preassigned magnitude threshold. Here, we review the fundamental ideas of an integrated approach to earthquake prediction, based on the synergy of high-density geodetic observations (GNSS and SAR) and seismological information, and the results obtained so far through a completely new retrospective analysis of the 2016–17 seismic crisis in Central Italy and the 2012 Emilia sequence, where space-time precursory features are highlighted within intermediate-term ground velocities and seismicity. This integrated approach defines a new paradigm for time-dependent hazard assessment scenarios, and it is demonstrated that the proper integration of seismological and geodetic information can achieve what here is called intermediate-term narrow-range earthquake prediction. The extent of the alarmed areas, identified for the strong earthquakes by earthquake prediction algorithms based on seismicity patterns, can be significantly reduced from linear dimensions of a few hundred to a few tens of kilometers, leading to an improved more specific implementation of low-key preventive actions, like those recommended by UNESCO as early as in 1991.

The Neo Deterministic Seismic Hazard Assessment (NDSHA) is the innovative multi‐disciplinary scenario‐physics‐based approach for the evaluation of seismic hazard and risks. When an earthquake occurs, the ground shaking does not depend on its likelihood according to the widespread Probabilistic Seismic Hazard Analysis (PSHA), which estimates are too often wrong. An “unlikely” earthquake can occur at any time and, sooner or later, with 100% probability. Therefore, from a perspective of safety, it is essential that infrastructure and public installations are designed so as to resist future strong earthquakes. NDSHA has proven to both reliably and realistically simulate comprehensive sets of hazardous ground motions in many regions worldwide. Today NDSHA is gaining momentum in spreading worldwide an innovative Paradigm of Reliable Seismic Hazard Assessment (RSHA) that should ultimately change mind‐sets of scientific and engineering communities from disbelief in probabilistic forecasting to optimistic challenging issues of neo‐deterministic predictability of Natural Hazards and Risks.

The Horizontal-to-Vertical Spectral Ratio (HVSR) obtained from microtremor data recorded at three test sites are analyzed in order to highlight some issues related to the computation of the SESAME criteria that define the statistical robustness of possible peaks. In case of multiple-peak HVSR curves, it is shown that to properly assess the statistical properties of a peak and avoid the problem of multimodal data distribution, it is crucial to isolate each peak by reducing the frequency range around it. It is also shown that, while the standard approach used to obtain a homogeneous data set is represented by the removal of large-amplitude transient events before the computation of the HVSR, the removal of outlier HVSR curves can be a more effective way to obtain such a goal, being outlier HVSR curves not necessarily associated to large-amplitude transient events. It is eventually briefly discussed the problem of the proper management of multi-peak HVSR curves in microzonation studies while defining the so-called soil frequency maps. It is argued that to focus these maps just on the lowest-frequency (f0) value is questionable because higher-frequency peaks can be much more important when the local urban landscape is characterized by low-rise buildings.

In the neo-deterministic seismic hazard assessment (NDSHA) evaluation, great-earthquake-prone areas (GEPAs) play an important role in defining the 'controlling earthquakes' or 'scenario earthquakes'. When considering great earthquakes, their finite rupture attributes, which contribute to determine the strong ground motions and intensities, have to be taken into account. For continental earthquakes in China, the great earthquakes are located mainly within the boundary zones of the 'tectonic blocks'. The 'tectonic block' model indicates the focal mechanisms and some finite rupture attributes of the great earthquakes within the boundary zones. Accordingly, in the NDSHA for China, it is both necessary and feasible for the GEPAs to consider the finite rupture attributes of great earthquakes. The Sichuan-Yunnan border in southwest China has been taken as an example to naturally develop the originally used circular shape of GEPAs into one with more degrees-of-freedom, better reflecting the possible rupture processes of the considered earthquakes.

Carbon dragged at sub-arc depths and sequestered in the asthenospheric upper mantle during cold subduction is potentially released after millions of years during the breakup of continental plates. However, it is unclear whether these deep-carbon reservoirs can be locally remobilized on shorter-term timescales. Here we reveal the fate of carbon released during cold subduction by analyzing an anomalously deep earthquake in December 2020 in the lithospheric mantle beneath Milan (Italy), above a deep-carbon reservoir previously imaged in the mantle wedge by geophysical methods. We show that the earthquake source moment tensor includes a major explosive component that we ascribe to carbon-rich melt/fluid migration along upper-mantle shear zones and rapid release of about 17,000 tons of carbon dioxide when ascending melts exit the carbonate stability field. Our results underline the importance of carbon-rich melts at active continental margins for emission budgets and suggest their potential episodic contributions to atmospheric carbon dioxide. A deep, magnitude 4.6 earthquake, beneath Milan, Italy, in December 2020 involved a major explosive component that may indicate outgassing of carbon dioxide from ascending carbonate-rich melts, according to moment tensor inversion of the seismic source.

Natural disasters, increasing in their frequency and complexity, damage infrastructure and hinder economic growth, cause death and injury, and increase the risk of infectious disease outbreaks. The Circum-Pannonian region is a well-defined seismically active region in Europe, and a single strong earthquake here may trigger a major catastrophe due to the densely populated areas and the presence of high-risk industrial facilities—chemical industry plants, nuclear power plants, dams, etc. To keep the life of the European citizens and the normal functioning of the society during and after a strong earthquake, it is necessary to work consistently and persistently toward seismic risk mitigation via reliable earthquake hazard assessment. Recent destructive earthquakes have shown a clear discrepancy between the predicted ground motion levels, estimated via the traditional probabilistic seismic hazard assessment method and the instrumental observations (e.g., L'Aquila—Italy (2009), Haiti (2010), Chile (2010), Japan (2011), Emilia—Romagna Italy (2012), Central Italy (2016), Ischia—Italy (2017), Gansu—China (2013)). These very important lessons indicate the necessity to revise and improve the seismic hazard assessment tools. A reliable seismic hazard estimation needs to be fully proven against available data and known scenarios—it is possible relying on integrated available information provided by seismological, geological, geophysical, and geotechnical databases coupled with advanced physical modeling techniques. To keep the critical infrastructure resilient, it is necessary to count on tools for seismic hazard assessment that are capable to provide relevant seismic input at different scales—regional, national, and metropolitan. The neo-deterministic seismic hazard assessment (NDSHA) meets all these necessities. In this paper, a summarizing overview of the multiaspect power of the neo-deterministic seismic hazard assessment is presented, supported by successful NDSHA applications within Central and South-eastern Europe.

The earthquake record shows that the territory of the Republic of Bulgaria is exposed to a high seismic risk due to local shallow and regional strong intermediate-depth earthquake sources—this fact is considered by the Code for design and construction in seismic regions in Bulgaria. Many modern sophisticated buildings and structures need comprehensive full time-history analysis at the design phase, which require modeling of the earthquake excitation via time histories. It is well known that the available strong motion database is quite limited, and therefore not representative of the real hazard—it clearly indicates the need of theoretically generated realistic seismic signals that can be used for further engineering analyses. The neo-deterministic seismic hazard assessment (NDSHA) procedure has been proven to be a very suitable one and supplies a significant database of realistic synthetic strong motions readily applicable for earthquake engineering purposes. A major advantage of the applied scenario-based procedure is the physically sound simultaneous consideration of the contribution of both the seismic source and the seismic wave pathway to the strong ground motion at each target site. In this study, we discuss the NDSHA applications in the study area: positive aspects and faced challenges.

This paper aims to suggest the most advanced and reliable way of analyzing the seismic hazard of an area located in Albania, where large-scale seismic events are very important. This area extends from Shkumbini River in the south up to the city of Shkodra, in the north. During 20th century, 40% of the strongest seismic events that struck Albania have occurred here, beginning with the earthquake occurred in Shkodra on June 1, 1905 (M = 6.6). Two of the strongest seismic events that stroke Albania during the last 40 years have occurred in this geographic area as well, the earthquake of Lezhë-Shkodër (Montenegro earthquake) of April 15, 1979 (M = 6.9) and the most recent one, earthquake of Durrës on November 26, 2019 (M = 6.4). The region is known as one of the most active seismogenic zones in Albania and is located between some of the most important seismogenic lineaments of the country. Probabilistic Seismic Hazard Assessment values, predicted in 2013, do not exceed 0.18 g! The first neodeterministic seismic hazard assessment (NDSHA scenario studies) so far performed for Albania date back to 2001. In the area most severely affected by the M 6.4 earthquake of November 26, 2019, the NDSHA DGA (~PGA) value at the bedrock is around 0.3 g and well envelopes the ground motion observed in 2019 (https://earthquake.usgs.gov/earthquakes/eventpage/us70006d0m/shakemap/pga). In fact, large values have been observed where "amplification" factors of 4–5, with respect to the shaking experienced at bedrock sites, are expected.

We propose an interdisciplinary approach to Time-dependent Neo-deterministic Seismic Hazard Assessment (T-NDSHA) for the China Seismic Experimental Site (CSES) at a one-year time scale. The approach is based on the Neo-deterministic Seismic Hazard Assessment (NDSHA), with the “controlling earthquakes” (or “scenario earthquakes”) as defined by the Annual Consultation on the Likelihood of Earthquakes. The Annual Consultation, organized by the China Earthquake Administration (CEA), has been an interdisciplinary practice since 1972, with the output of “alert regions” with increased probabilities of strong earthquakes, featured by real forward forecasting characteristics. We take the year 2014, in which there were four strong earthquakes in the CSES region, as a showcase example to illustrate how the T-NDSHA may be conducted and evaluated. Considering the alert regions provided by the Annual Consultation, the expected strong ground motion parameters and the macroseismic intensities are mapped by the NDSHA algorithms considering the regional Earth structures and the focal mechanisms of historical earthquakes. The estimated intensities are then compared with the observed intensities produced by the actual earthquakes. Evaluation of the performance of such annual seismic hazard assessment is performed using a confusion matrix and Molchan error diagram, respectively, indicating that the combination of the NDSHA and the annual forecasting provides the emergency preparation with a ready-to-use mapping of expected intensities which outperforms random forecasting. The proposed approach provides a substantial improvement to the Annual Consultation, and it can naturally be applied to other regions where intermediate-term middle-range earthquake forecasts are available and where the need for emergency preparation are duly considered.

In this paper, we discuss a possible combination of Earthquake Early Warning (EEW) and Neo-deterministic Seismic Hazard Assessment (NDSHA), and propose a new warning model, EEW2.0. The aim is to provide a differentiated warning alert to various end-users based on the results of seismic hazard assessment evaluation. The implementation of such a system contains three basic steps: (a) classification of “potential to cause hazard” in terms of magnitude; (b) determination of the source areas and building a hazard database in terms of Modified Mercalli Intensity (MMI) maps, considering all possible earthquake scenarios in the source area, for the whole protected area; (3) equipping unique decision framework for specific end-users. When a damaging earthquake (M ≥ 5.0) is detected, EEW2.0 quickly matches the prepared MMI map by estimated magnitude and epicenter, then directly extracts the MMI value and issues an early warning to the public. With the great attention and resources put into the reduction in seismic and its secondary risk in the 21st century, the proposed EEW2.0 will likely play an active role in protecting lives and reducing economic losses.

Many devastating earthquakes inflicted heavy casualties and property losses in the seismically active China Seismic Experimental Site area (CSES: 97.5 degrees similar to 105.5 degrees E, 21 degrees similar to 32 degrees N). We performed a first-order seismic zoning based on Neo-deterministic Seismic Hazard Assessment (NDSHA) in the study area delimited by 94 degrees similar to 108 degrees E and 19 degrees similar to 35 degrees N, containing the South-East margin of the Tibetan Plateau and the Sichuan-Yunnan region. The seismic hazard is expressed by maps of peak ground displacement (PGD), peak ground velocity (PGV) and design ground acceleration (DGA) values, extracted from synthetic seismograms computed at a regional scale and mapped on a regular grid of 0.2 degrees x 0.2 degrees over the study area. For the computation of synthetic seismograms, we considered and updated all the available geophysical-geological-tectonic information, including historical and instrumental earthquake catalogues, seismogenic zones, seismogenic nodes, focal mechanisms, and geophysical structural models. We tested the performance of our assessments with available data (i.e., after the Great Wenchuan (2008, May 12th, M-s = 8.0) and Lushan (2013, April 20th, M-s = 7.0) earthquakes) and verified the negligible influence of large events located "far" from the study area. The results indicate the high seismic hazard of the region, with a particular attention (i.e., where DGA > 0.6 g) to the areas located around the main fault zones, e.g., the Longmenshan, Anninghe and Zemuhe Fault Zones. These first-order NDSHA zoning findings may serve as a knowledge basis to support both large- to mid-range preparedness actions and (multi-scenario) site-specific studies.

Kosovo is one of the most seismically active regions in Europe, lying within the Alpine-Mediterranean tectonic belt. Historical records for the region show several catastrophic earthquakes with epicentral intensity IX (MCS). However, due to Kosovo's high population density, high prevalence of traditional construction, and insufficient enforcement of building codes, Kosovo is vulnerable to earthquake damage. In this study, we present earthquake hazard maps for bedrock conditions in Kosovo based on the well-known Neo-deterministic Seismic Hazard Assessment (NDSHA) method. NDSHA relies upon the fundamental physics of wave generation and propagation in complex geologic structures to generate realistic time series, used as input for the computation of several ground motion parameters, integrating the available knowledge of seismic history, seismogenic zones and morphostructural nodes. In accordance with continuum mechanics, the tensor nature of earthquake ground motion is preserved, producing realistic signals using structural models obtained by tomographic inversion and earthquake source information readily available in literature. Our maps are generally consistent with the observed intensity IX (MCS) and suggest that, in some instances, intensity X could be reached.