Nomograms are an easy to use and visually attractive graphical tool to solve for any of the variables within an often complex equation. In seismology, the most well-known nomogram is a ...three-parallel-scale graphic for the calculation of local magnitude given the epicentral distance and trace amplitude. Until the advent of computers, nomograms were often employed by engineers and scientists in many fields as they provide a means for rapid and accurate calculations as well as helping the user understand the sensitivity of the final results to the input parameters. It is this aid to understanding that remains a key attraction of these graphical tools, which are now rarely seen (although they remain common in some fields of medicine where they are used for rapid screening and estimating risks). In this research letter, we present a nomogram summarising the results of simple probabilistic seismic hazard assessments (PSHAs) for peak ground acceleration and elastic response spectral acceleration for a structural period of 1s and return periods from 100 to 2500 years, where the effects of the activity rate and the slope of the Gutenberg-Richter relation are captured. We believe that this nomogram has considerable educational benefit for engineering seismology students, decision makers and other non-expert users of results of PSHAs.
The 2013 European Seismic Hazard Model (ESHM13) results from a community-based probabilistic seismic hazard assessment supported by the EU-FP7 project “Seismic Hazard Harmonization in Europe” (SHARE, ...2009–2013). The ESHM13 is a consistent seismic hazard model for Europe and Turkey which overcomes the limitation of national borders and includes a through quantification of the uncertainties. It is the first completed regional effort contributing to the “Global Earthquake Model” initiative. It might serve as a reference model for various applications, from earthquake preparedness to earthquake risk mitigation strategies, including the update of the European seismic regulations for building design (Eurocode 8), and thus it is useful for future safety assessment and improvement of private and public buildings. Although its results constitute a reference for Europe, they do not replace the existing national design regulations that are in place for seismic design and construction of buildings. The ESHM13 represents a significant improvement compared to previous efforts as it is based on (1) the compilation of updated and harmonised versions of the databases required for probabilistic seismic hazard assessment, (2) the adoption of standard procedures and robust methods, especially for expert elicitation and consensus building among hundreds of European experts, (3) the multi-disciplinary input from all branches of earthquake science and engineering, (4) the direct involvement of the CEN/TC250/SC8 committee in defining output specifications relevant for Eurocode 8 and (5) the accounting for epistemic uncertainties of model components and hazard results. Furthermore, enormous effort was devoted to transparently document and ensure open availability of all data, results and methods through the European Facility for Earthquake Hazard and Risk (
www.efehr.org
).
In this study focused on France, we explore the uncertainties related to choices made while building a source model for hazard assessment and we quantify the impact on probabilistic hazard estimates. ...Earthquake recurrence models are initially built from the French Seismic CATalog (FCAT, Manchuel et al. in Bull Earthq Eng, 2018.
https://doi.org/10.1007/s10518-017-0236-1
). We set up a logic tree that includes two alternative seismogenic source models (ESHM13 and Baize et al. in Bull Soc Géol Fr 184(3):225–259, 2013), two versions of FCAT catalog, two alternative declustering algorithms, and three alternative minimum magnitudes for earthquake recurrence modeling. We calculate the hazard for six cities (i.e. Nantes, Lourdes, Clermont-Ferrand, Briançon, Nice and Strasbourg) that are located in source zones with a minimum amount of data to work with. Results are displayed for the PGA and spectral period 0.2 s, at return periods 475 and 5000 years. Exploration of the logic tree shows that the parameters with the most impact on hazard results are the minimum magnitude used in the recurrence modeling (up to 31%) and the selection of the seismogenic source model (up to 30%). We also use the SHARE European Earthquake Catalog (SHEEC, Woessner et al. in Bull Earthquake Eng, 2015.
https://doi.org/10.1007/s10518-015-9795-1
) to build earthquake recurrence models and compare hazard values obtained with the FCAT logic tree. Comparisons are limited because of the low number of events available in some sources in SHEEC; however, results show that, depending on the site considered, the earthquake catalog selection can also strongly impact the hazard estimates (up to 50%). The FCAT logic tree is combined with four ground-motion models (Bindi et al. in Bull Earthq Eng 12(1):391–430, 2014; Boore et al. in Earthq Spectra 30(3):1057–1085, 2014; Cauzzi et al. in Bull Earthq Eng 13(6):1587–1612, 2015.
https://doi.org/10.1007/s10518-014-9685-y
; Drouet and Cotton in Bull Seismol Soc Am 105(4):1883–1902, 2015) to account for the epistemic uncertainty on the prediction of ground-motion. Exploration of the logic tree shows that the contribution of ground-motion model uncertainties can be larger than, equivalent to, or lower than the contribution of the source-model uncertainties to the overall hazard variability. Which component controls overall uncertainty depends on the site, spectral period and return period. Finally, exploring the logic tree provides a distribution for the ratios between hazard levels at 5000 and 475 years return periods, revealing that the ratios only slightly depend on source-model uncertainties, vary strongly from site to site, and can take values between 3 and 5, which is significantly higher than what is commonly assumed in the engineering community.
In this study, we present the work done to review the existing historical earthquake information of the Dead Sea Transform Fault Zone (DSTFZ). Several studies from various sources have been collected ...and reassessed, with the ultimate goal of creating of new homogenized parametric earthquake catalog for the region. We analyze 244 earthquakes between 31 BC and 1900, which are associated with the geographical buffer extending from 27 N to 36 N and from 31 E to 39 E. Of these, 93 were considered real seismic events with moment magnitude (
M
w
) greater than 5 that indeed occurred within this zone. While we relied on past parametric data and did not assign new macroseismic intensities, magnitude values, or epicenters for several controversial events, we did however resort to the primary sources to obtain a more critical perspective for the various assigned macroseismic intensities. In order to validate the derived parametric information, we tried to associate the events present in the historical records, with any evidence coming from past field investigations, i.e., geological or archaeological studies. Acknowledging the uneven quality and quantity of data reporting each event, we provided each entry with an uncertainty range estimate. Our catalog lists 33 events of
M
w
≥ 6 absent from the latest published compilation with compatible time span and areal coverage. The whole catalog is considered complete down to
M
w
7 and in certain areas down to
M
w
6 after the year 1000, with majority of the larger earthquakes located in the part of DSTFZ, which extends from the southeast part of Dead Sea lake till Antioch.
The creation of a homogenized earthquake catalog is a fundamental step in seismic hazard analysis. The homogenization procedure, however, is complex and requires a good understanding of the ...heterogeneities among the available bulletins. Common events within the bulletins have to be identified and assigned with the most suitable origin time and location solution, while all the events have to be harmonized into a single magnitude scale. This process entails several decision variables that are usually defined using qualitative measures or expert opinion, without a clear exploration of the associated uncertainties. To address this issue, we present an automated and data-driven workflow that defines spatio-temporal margins within which duplicate events fall and converts the various reported magnitudes into a common scale. Special attention has been paid to the fitted functional form and the validity range of the derived magnitude conversion relations. The proposed methodology has been successfully applied to a wide region around the Dead Sea Transform Fault Zone (27N-36N, 31E-39E), with input data from various sources such as the International Seismological Centre and the Geophysical Institute of Israel. The produced public catalog contains more than 5500 events, between 1900 and 2017, with moment magnitude Mw above 3. The MATLAB/Python scripts used in this study are also available.
Global Seismic Hazard Assessment Program - or simply GSHAP, when launched, almost two decades ago, aimed at establishing a common framework to evaluate the seismic hazard over geographical ...large-scales, i.e. countries, regions, continents and finally the globe. Its main product, the global seismic hazard map was a milestone, unique at that time and for a decade have served as the main reference worldwide. Today, for most of the Earth’s seismically active regions such Europe, Northern and Southern America, Central and South-East Asia, Japan, Australia, New Zealand, the GSHAP seismic hazard map is outdated. The rapid increase of the new data, advance on the earthquake process knowledge, technological progress, both hardware and software, contributed all in updates of the seismic hazard models. We present herein, a short retrospective overview of the achievements as well as the pitfalls of the GSHAP. Further, we describe the next generation of seismic hazard models, as elaborated within the Global Earthquake Model, regional programs: the 2013 European Seismic Hazard Model, the 2014 Earthquake Model for Middle East, and the 2015 Earthquake Model of Central Asia. Later, the main characteristics of these regional models are summarized and the new datasets fully harmonized across national borders are illustrated for the first time after the GSHAP completion.
With seismic risk assessments becoming more available and reliable over the last years, the need to communicate seismic risk emerged. Seismic risk allows people to understand what impacts earthquakes ...can have and how they could affect their lives. In Switzerland, a nation-wide seismic risk model (ERM-CH23) was published in 2023 demanding sophisticated communication products to inform about its results. Since only limited research has been conducted on how to best communicate earthquake risk information to societies including the general public, key elements of the outreach activities were tested before the model release. To this end, we, an interdisciplinary group, conducted a nationwide survey in Switzerland in December 2022 to test different earthquake risk map designs by varying the color scale and the legend type. We analyzed the effects of the map and legend design on people's correct interpretation of the risk information, perceived usefulness, risk perception, and motivation to take action. Our survey revealed that (i) a legend with the combination of qualitative and quantitative labels leads to more accurate interpretations of the information presented on the map and is preferred by the public; (ii) the color scale determines how people perceive the spatial risk; and (iii) personal factors influence people's interpretation skills, risk perception, and intention to take action. Our study thus provides insights and recommendations on how to best design user-centered earthquake risk maps as a key outreach product to ensure their effective use by the public, consequently enhancing society's resilience to earthquakes in the long term.
Central Asia is one of the seismically most active regions in the world. Its complex seismicity due to the collision of the Eurasian and Indian plates has resulted in some of the world’s largest ...intra-plate events over history. The region is dominated by reverse faulting over strike slip and normal faulting events. The GSHAP project (1999), aiming at a hazard assessment on a global scale, indicated that the region of Central Asia is characterized by peak ground accelerations for 10% probability of exceedance in 50 years as high as 9 m/s2. In this study, carried out within the framework of the EMCA project (Earthquake Model Central Asia), the area source model and different kernel approaches are used for a probabilistic seismic hazard assessment (PSHA) for Central Asia. The seismic hazard is assessed considering shallow (depth < 50 km) seismicity only and employs an updated (with respect to previous projects) earthquake catalog for the region. The seismic hazard is calculated in terms of macroseismic intensity (MSK-64), intended to be used for the seismic risk maps of the region. The hazard maps, shown in terms of 10% probability of exceedance in 50 years, are derived by using the OpenQuake software Pagani et al. 2014, which is an open source software tool developed by the GEM (Global Earthquake Model) foundation. The maximum hazard observed in the region reaches an intensity of around 8 in southern Tien Shan for 475 years mean return period. The maximum hazard estimated for some of the cities in the region, Bishkek, Dushanbe, Tashkent and Almaty, is between 7 and 8 (7-8), 8.0, 7.0 and 8.0 macroseismic Intensity, respectively, for 475 years mean return period, using different approaches. The results of different methods for assessing the level of seismic hazard are compared and their underlying methodologies are discussed.
Earthquakes cluster in space and time resulting in nonlinear damage effects. We compute earthquake interactions using the Coulomb stress transfer theory and dynamic vulnerability from the concept of ...ductility capacity reduction. We combine both processes in the generic multi-risk framework where risk scenarios are simulated using a variant of the Markov chain Monte Carlo method. We apply the proposed approach to the thrust fault system of northern Italy, considering earthquakes with characteristic magnitudes in the range ~6, 6.5, different levels of tectonic loading
τ
˙
= {10
−4
, 10
−3
, 10
−2
} bar/year and a generic stock of fictitious low-rise buildings with different ductility capacities
μ
Δ
= {2, 4, 6}. We describe the process’ stochasticity by non-stationary Poisson earthquake probabilities and by binomial damage state probabilities. We find that earthquake clustering yields a tail fattening of the seismic risk curve, the effect of which is amplified by damage-dependent fragility due to clustering. The impact of clustering alone is in average more important than dynamic vulnerability, the spatial extent of the former phenomenon being greater than of the latter one.
Regional, multi-country seismic hazard models provide a comparison basis for national seismic hazard models that are generally used to underpin the seismic design prescriptions of national building ...codes. Our study presents an attempt to formalize a framework for performing such a comparison. This comparison consists of sequential steps for identifying and understanding similarities of the key elements informing the seismic hazard models and the code design ground motions in addition to their numerical comparison. The challenge may arise, on one hand, from the lack of transparency of some national seismic codes and, on the other hand, from the intrinsic difficulties in comparing seismic hazard models. In this study, as an example we compare the seismic design spectrum of the Iranian national design code with the uniform hazard spectra from the recent, fully-harmonized, cross-borders Earthquake Hazard Model for the Middle East region (EMME). This comparison focuses on the two 10% in 50-year exceedance probability maps for PGA and on the pairs of design spectra for four cities with different seismicity levels. While, in general, the two reference maps for PGA on rock seem similar, the comparison of the uniform hazard spectra and design spectra for the four selected cities for different soil conditions show large differences. We offer some plausible causes for these differences as well as generic recommendations for overcoming them.
•Establishing a framework to perform a comprehensive comparison between two PSHA studies and/or hazard maps.•Implementation of the comparison framework to a recent regional PSHA for Middle East Region (EMME14) with the seismic zonation map of the national design code of Iran (Code 2800).•Recommendations on improvements of the seismic zonation map of Iran.
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