The 2013 European Seismic Hazard Model: key components and results

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)

The 2013 European seismic hazard model : key components and results

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)

The 2013 European Seismic Hazard Model: key components and results

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)

Strong ground motion in the epicentral area of the 2020-2021 earthquake swarm in the Reykjanes Peninsula, Iceland

The Geldingadalur eruption in the Reykjanes Peninsula on 19 March 2021 was preceded by several earthquakes of volcano-tectonic origin throughout 2020 and 2021. Seven earthquakes with magnitude M≥5 took place during the swarm, all of them recorded by the Icelandic Strong Motion Network operated by the Earthquake Engineering Research Centre of the University of Iceland. In this paper we present salient features of strong ground motion in the epicentral area caused by the swarm. Interestingly, earthquakes as small as M5.0 caused peak ground acceleration (PGA) larger than the 475-year return period PGA at a town near the epicentral area. At two recording stations, unusually high energy content at vibration periods <0.3s was detected, with spectral accelerations exceeding the design values. The largest recorded horizontal PGA was ~0.4g at Krýsuvík, station, which is the strongest PGA recorded in Iceland since the MW6.3 2008 Ölfus Earthquake. For this station we present horizontal-to-vertical spectral ratios indicating likely site-effects. We also compare the attenuation of PGA of the largest event of the sequence with two groundmotion prediction equations (GMPEs). The recorded PGA attenuation is well captured by a local GMPE.This work was partly financed by the SERICE project funded by a Grant of Excellence from the Icelandic Centre for Research (RANNIS), Grant number: 218149-051. The authors also acknowledge support from the University of Iceland Research Fund. The authors wish to thank the Icelandic Meteorological Office for access to the earthquake catalogue.Peer Reviewe

High spatial-resolution loss estimation using dense array strong-motion near-fault records. Case study for Hveragerði and the Mw 6.3 Ölfus earthquake, South Iceland

The most recent and costliest damaging earthquake in Iceland is the w6.3 29-May-2008 Ölfus earthquake to date. In particular, Hveragerði town located in the extreme near-fault region, suffered intense horizontal peak ground accelerations (PGA) of ∼40–90%g and large amplitude and long-period near-fault pulses, recorded on a dense urban strong-motion array in the town. In this study we collated a high-spatial resolution exposure database (building-by-building) complete with actual reported losses and classified the buildings by building materials and construction year according to the code design requirements in place at the time. We took advantage of the array data and evaluated a set of well-known ground motion intensity measures (IM), including PGA, pseudo-acceleration response spectra at short-to-long periods, Arias Intensity and Cumulative Absolute Velocity. We applied empirical Bayesian kriging geostatistical analyses to generate high-resolution shakemaps and provide IM estimates for each building. The shakemaps showed significant and systematic variation of the IMs across the small study area, with the lowest ground motions observed centrally and highest values in the outskirts. Furthermore, correlation analysis was carried out for the damage ratio and the exposure data IMs, but only low-to-moderate correlations were observed. A key reason is the incurred losses were primarily due to damage to non-structural components, to which the code design requirements do not apply. We carried out a seismic loss assessment in Hveragerði for the earthquake scenario of the Ölfus earthquake both on building-by-building, and municipality levels of spatial resolution. We applied both local and global fragility models for associated with detail building typologies identified based on the SERA taxonomy scheme. The results show that the global fragility functions severely underestimate the seismic performance of the building stock, except for one-story reinforced concrete buildings, while overall the masonry buildings were associated with the most predicted and observed losses. On the other hand, the local models predicted losses that conformed well with the observed damages to timber and concrete buildings. The high-spatial resolution predictions of losses gave results that better correlated with the observed losses in most typologies.This study was funded by the TURNkey H2020 European project (Towards more Earthquake-Resilient Urban Societies through a Multi-Sensor-Based Information System enabling Earthquake Forecasting, Early Warning and Rapid Response Actions) [www.earthquake-turnkey.eu] under grant agreement No 821046. This work was facilitated by an Erasmus+ staff mobility grant No. IS-TS2020-87850 for the lead author to the University of Alicante, Spain. This work was also partly supported by a Postdoctoral fellowship (No. 218255-051), grant of excellence (No. 218149-051) from the Icelandic Research Fund of the Icelandic Centre for Research, and the University of Iceland Research Fund

Probabilistic seismic hazard assessment framework for Uganda: a stochastic event-based modelling approach

Uganda lies between the eastern and western arms of the East African Rift System, the largest seismically active rift above sea level. With increasing population, urbanisation and rapid construction, seismic risk in the country is escalating fast and is compounded by the high vulnerability of the building stock and inadequate disaster prevention and mitigation strategies. Hence, there is an urgent need to assess Uganda’s resilience against seismic risks. This paper presents a Monte-Carlo based probabilistic seismic hazard model for Uganda, as the first step towards the development of a seismic risk and resilience assessment framework for the country. In addition to fault segment data, earthquake catalogues are compiled for the period between 1900 and 2022 to estimate recurrence parameters for source zones in the area of interest. Area source zones incorporating focal mechanisms are used to stochastically model a national hazard framework for Uganda. A logic tree approach is applied to implement four ground motion prediction equations for both stable continental and active shallow crust geologies. Mean hazard curves, uniform hazard spectra, earthquake disaggregation and spectral pseudo-accelerations for major Ugandan cities are derived in addition to hazard maps for the country. The findings are largely consistent with previous regional studies and confirm that western Uganda is exposed to the highest level of seismicity. The model presented herein can be used to kick-start the update and continuous improvement of Uganda Seismic Design Code and the National Policy for Disaster Preparedness and Management

National seismic hazard maps for the UK: 2020 update

This report is the published product of a study by the British Geological Survey (BGS) to update the national seismic hazard maps for the UK. This is to take account of advances in seismic hazard methodology since the last seismic hazard maps were developed by Musson and Sargeant (2007) and present the results in a format that will be compatible with the future Eurocode 8 revisions

Earthquake Seismology 2015/2016

The British Geological Survey (BGS) operates a network of seismometers throughout the UK in order to acquire seismic data on a long-term basis. The aims of the Seismic Monitoring and Information Service are to develop and maintain a national database of seismic activity in the UK for use in seismic hazard assessment, and to provide near-immediate responses to the occurrence, or reported occurrence, of significant events. The project is supported by a group of organisations under the chairmanship of the Office for Nuclear Regulation (ONR) with major financial input from the Natural Environment Research Council (NERC). In the 27th year of the project, one new broadband seismograph station was established, giving a total of 44 broadband stations. New strong motion instrumentation was also installed at an existing site. Real-time data from all stations are being transferred directly to Edinburgh for near real-time detection and location of seismic events as well as archival and storage of continuous data. Data latency is generally low, less than one minute most of the time, and there is a high level of completeness within our archive of continuous data. All significant events were reported rapidly to the Customer Group through seismic alerts sent by e-mail. The alerts were also published on the Internet (http://www.earthquakes.bgs.ac.uk). Eleven papers have been published in peer-reviewed journals. Two presentations were made at international conferences. Five BGS reports were prepared. We have continued to collaborate widely with academic partners across the UK and overseas on a number of research initiatives