Conversion between the local magnitude (ML) and the moment magnitude (Mw) for earthquakes in the Croatian Earthquake Catalogue

Na temelju podataka o lokalnoj magnitudi (ML,CR) iz Hrvatskog kataloga potresa, izvedena je konverzijska relacija između ML,CR i momentne magnitude Mw koju su za odabrane potrese javile svjetske i regionalne agencije. Odabrana je tzv. Yorkova regresija koja je prikladna u slučaju da su mjerne pogreške prisutne kod obje varijable. Najbolju prilagodbu postiže se relacijom MwL = (–0,106 ± 0,122) + (1,002 ± 0,027) ML,CR (uz koeficijent determinacije R2 = 0,90). Odabrani potresi dogodili su se u Hrvatskoj i susjednim područjima, a imali su lokalne magnitude između 3,5 i 6,5. Analiza odstupanja ukazuje na mogućnost da se u katalogu početkom 1980-ih dogodio umjetni pozitivni skok u magnitudi ML,CR od ne više od 0,3 jedinice magnitude. Do njega je vjerojatno došlo pri zamjeni Wiechertovih seizmografa elektromagnetskima bez adekvatne korekcije magnitudne formule. Nagib pravca regresije vrlo blizak jedinici ukazuje da je prosječni omjer kraće i dulje stranice uzročnih rasjeda oko 1/2.Based on 153 earthquakes (1959–2020) listed in the Croatian Earthquake Catalogue, a conversion relation was obtained between the local magnitude ML,CR and the corresponding moment magnitude Mw as reported by the global and regional agencies. As errors were present in both variables the York regression was used. The best fit line is given by: MwL = (–0.106 ± 0.122) + (1.002 ± 0.027) ML,CR (coefficient of determination R2 = 0.90). The earthquakes considered occurred in Croatia and the neighbouring regions, and their local magnitudes ML,CR ranged between 3.5 and 6.5. Residual analysis suggests that an artificial positive magnitude shift of up to 0.3 magnitude units may have occurred in the early 1980s, when Wiechert mechanical seismographs were replaced by the instruments with velocity proportional recordings without proper recalibration of the magnitude formula. The slope of the regression close to 1.0 indicates that on the average the faults’ aspect ratio (width/length) is about 1/2

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)

Earthquake-induced landslide hazard assessment in the Vrancea Seismic Region (Eastern Carpathians, Romania): Constraints and perspectives

peer reviewedIn seismically-active regions, earthquake-induced landslides (EqIL) are likely to enhance slope denudation and sediment delivery both over short and longer terms, which might strongly condition landscape evolution in general. In mountain regions marked by a medium to high seismicity, co-seismic slope failures typically present a relatively low frequency but also high magnitude pattern which should be addressed accordingly within landslide hazard assessment, considering the already high frequency of precipitation-triggered landslide events. The Vrancea Seismic Region located in the curvature sector of the Eastern Carpathians (Romania) is the most active intermediate-depth seismic zones (focal depth > 70 km) in Europe. It represents the main seismic energy source throughout Romania with significant transboundary effects recorded as far as Ukraine and Bulgaria. During the last 300 years, the region featured 13 earthquakes with magnitudes (Mw) above 7, out of which seven events had Mw above 7.5 and three between 7.7 and 7.9. Apart from the direct damages, the Vrancea earthquakes are also responsible for causing numerous other geohazards, such as ground fracturing, groundwater level disturbances and deep-seated landslide occurrences (e.g. rock slumps, rock-block slides, rock falls, rock avalanches). The previous large earthquake-induced deep-seated landslides of the Vrancea region were found to affect the entire slope profile. They often formed landslide dams which strongly influenced the river morphology, posing a serious threat to human life and human facilities of the downstream rural communities through the imminent lake outburst floods. Despite the large potential of this research issue, the correlation between the region's seismotectonic context and landslide geomorphic predisposing factors has not been extensively documented and fully understood yet. Presently, the available geohazard inventories provide limited historical information to quantify the triggering role of seismic activity for observed slope failures across the Vrancea region. However, it is acknowledged that the morphology and geology of numerous large, deep-seated and dormant landslides of this region, which may be reactivated in future, with head scarps near mountain tops and located close to faults, in anti-dip slope conditions show significant similarities to the large mass movements with a proven seismic origin (such as in the Tien Shan, Pamir, Longmenshan, etc.). Thus, the relationship between landslide occurrences and the joint action of triggers and preparing factors (seismotectonic or climatic or both) needs to be investigated in more detail and further considered in the regional multi-hazard risk assessments. The purpose of this paper is to outline the current knowledge level of the landslide-earthquake relationship by accounting for the possible effects of the previous major earthquakes in the Vrancea region. The key findings contribute to the gain of the baseline knowledge for an improved assessment framework of multi-hazard (earthquake-landslide) risks, as required by the Sendai Framework for Disaster Risk Reduction (SFDRR)

Satellite-based emergency mapping using optical imagery: experience and reflections from the 2015 Nepal earthquakes

Landslides triggered by large earthquakes in mountainous regions contribute significantly to overall earthquake losses and pose a major secondary hazard that can persist for months or years. While scientific investigations of coseismic landsliding are increasingly common, there is no protocol for rapid (hours-to-days) humanitarian-facing landslide assessment and no published recognition of what is possible and what is useful to compile immediately after the event. Drawing on the 2015 Mw 7.8 Gorkha earthquake in Nepal, we consider how quickly a landslide assessment based upon manual satellite-based emergency mapping (SEM) can be realistically achieved and review the decisions taken by analysts to ascertain the timeliness and type of useful information that can be generated. We find that, at present, many forms of landslide assessment are too slow to generate relative to the speed of a humanitarian response, despite increasingly rapid access to high-quality imagery. Importantly, the value of information on landslides evolves rapidly as a disaster response develops, so identifying the purpose, timescales, and end users of a post-earthquake landslide assessment is essential to inform the approach taken. It is clear that discussions are needed on the form and timing of landslide assessments, and how best to present and share this information, before rather than after an earthquake strikes. In this paper, we share the lessons learned from the Gorkha earthquake, with the aim of informing the approach taken by scientists to understand the evolving landslide hazard in future events and the expectations of the humanitarian community involved in disaster response. Please read the corrigendum first before accessing the articl

Satellite-based emergency mapping using optical imagery: experience and reflections from the 2015 Nepal earthquakes

Landslides triggered by large earthquakes in mountainous regions contribute significantly to overall earthquake losses and pose a major secondary hazard that can persist for months or years. While scientific investigations of coseismic landsliding are increasingly common, there is no protocol for rapid (hours-to-days) humanitarian-facing landslide assessment and no published recognition of what is possible and what is useful to compile immediately after the event. Drawing on the 2015 Mw 7.8 Gorkha earthquake in Nepal, we consider how quickly a landslide assessment based upon manual satellite-based emergency mapping (SEM) can be realistically achieved and review the decisions taken by analysts to ascertain the timeliness and type of useful information that can be generated. We find that, at present, many forms of landslide assessment are too slow to generate relative to the speed of a humanitarian response, despite increasingly rapid access to high-quality imagery. Importantly, the value of information on landslides evolves rapidly as a disaster response develops, so identifying the purpose, timescales, and end users of a post-earthquake landslide assessment is essential to inform the approach taken. It is clear that discussions are needed on the form and timing of landslide assessments, and how best to present and share this information, before rather than after an earthquake strikes. In this paper, we share the lessons learned from the Gorkha earthquake, with the aim of informing the approach taken by scientists to understand the evolving landslide hazard in future events and the expectations of the humanitarian community involved in disaster response