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Bommer, J. J.
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Bommer, J. J.
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- PublicationOpen AccessComparisons among the five ground-motion models developed using RESORCE for the prediction of response spectral accelerations due to earthquakes in Europe and the Middle East(2014-02)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Douglas, J.; BRGM, Orléans, France ;Akkar, S.; Middle East Technical University, Ankara, Turkey ;Ameri, G.; FUGRO-Geoter, Auriol, France. ;Bard, P.; ISTerre, Grenoble, France ;Bindi, D.; GFZ, Potsdam, Germany ;Bommer, J.; Imperial College London, United Kingdom ;Bora, S. S.; Inst. Erd- und Umweltwissesnschaften, Universitaet Potsdam, Germany ;Cotton, F.; ISTerre, Grenoble, France ;Derras, B.; ISTerre, Grenoble, France ;Hermkes, M.; Inst. Erd- und Umweltwissesnschaften, Universitaet Potsdam, Germany ;Kuehn, N. M.; Inst. Erd- und Umweltwissesnschaften, Universitaet Potsdam, Germany ;Luzi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Massa, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Pacor, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Riggelsen, C.; Inst. Erd- und Umweltwissesnschaften, Universitaet Potsdam, Germany ;Sandikkaya, M. A.; Middle East Technical University, Ankara, Turkey ;Scherbaum, F.; Inst. Erd- und Umweltwissesnschaften, Universitaet Potsdam, Germany ;Stafford, P.; Imperial College London, United Kingdom ;Traversa, P.; EDF, Aix en Provence, France; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; This article presents comparisons among the five ground-motion models described in other articles within this special issue, in terms of data selection criteria, characteristics of the models and predicted peak ground and response spectral accelerations. Comparisons are also made with predictions from the Next Generation Attenuation (NGA) models to which the models presented here have similarities (e.g. a common master database has been used) but also differences (e.g. some models in this issue are nonparametric). As a result of the differing data selection criteria and derivation techniques the predicted median ground motions show considerable differences (up to a factor of two for certain scenarios), particularly for magnitudes and distances close to or beyond the range of the available observations. The predicted influence of style-of-faulting shows much variation among models whereas site amplification factors are more similar, with peak amplification at around 1s. These differences are greater than those among predictions from the NGA models. The models for aleatory variability (sigma), however, are similar and suggest that ground-motion variability from this region is slightly higher than that predicted by the NGA models, based primarily on data from California and Taiwan.214 263 - PublicationRestrictedA prioritization scheme for seismic intervention in school building in Italy(2007-05)
; ; ; ; ; ; ;Grant, D. N.; EUCENTRE, European Centre for Training and Research in Earthquake Engineering, 27100 Pavia, Italy ;Bommer, J. J.; Imperial College London, Civil & Environmental Engineering, London SW7 2AZ, U. K. ;Pinho, R.; University of Pavia, Department of Structural Mechanics, via Ferrata 1, 27100 Pavia, Italy ;Calvi, G. M.; European School for Advanced Studies in Reduction of Seismic Risk (ROSE School), 27100 Pavia, Italy ;Goretti, A.; Department of Civil Protection, National Seismic Service, via Vitorchiano 2, 00189 Rome, Italy ;Meroni, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; ; ; ; ; A seismic rehabilitation program is being implemented to address the vulnerability of a large proportion of Italian building stock. A risk management framework, initially only for Italian school buildings, has been developed to assign priorities for the rehabilitation, and to give timescales within which retrofit or demolition must take place. Since it is not practical to carry out detailed assessment for around 60,000 Italian schools, the framework is a multiple-level procedure that aims to identify the highest-risk buildings based on filters of increasing detail, and reduces the size of the building inventory at each step. Finally, priorities and timescales are assigned based on vulnerability, seismic hazard, and building occupancy, within a general framework with parameters that must be assigned by the relevant authorities. The methodology is transparent, technically based, and flexible enough to be adapted for other building types or regions.284 23 - PublicationRestrictedAn intensity database for earthquakes in South Africa from 1912 to 2011(2013)
; ; ; ; ; ; ; ;Midzi, V.; Council for Geoscience ;Bommer, J. J.; Imperial College ;Strasser, F. O.; Council for Geoscience ;Albini, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Zulu, B. S.; Council for Geoscience ;Prasad, K.; Council for Geoscience ;Flint, N. S.; Council for Geoscience; ; ; ; ; ; A database of intensity observations from instrumentally-recorded earthquakes in South Africa has been compiled as a contribution to the characterisation of seismic hazard. The database contains about 1,000 intensity data points (IDPs) that have been assigned from macroseismic observations retrieved from newspaper reports and questionnaires, and also digitised from previously published isoseismal maps. The database includes IDPs from 57 earthquakes with magnitudes in the range of Mw 2.2 to 6.4, for epicentral distances up to 1,000 km. Sixteen events have 20 or more IDPs, with half of these events having more than 80 IDPs. The database is dominated by relatively low intensity values, mostly determined from human perception of shaking rather than structural damage. However, 19 IDPs correspond to intensity values greater than VI MMI-56. Using geological maps of South Africa, the sites of 60% the IDPs were geologically classified as either ‘rock’ or ‘soil’, the uncertainty in locations precluding such a classification for the remaining data points. A few of the IDPs identified as being from soil sites appear to be strongly influenced by site effects and these were removed from the trimmed database created for exploring ground-motion levels. The trimmed database included 15 earthquakes which have a minimum of five useful IDPs, excluding those with intensity MMI=I and those based on a single observation. After removing such points, and those identified as clear ‘outliers’, a total of 436 useful IDPs were selected.443 23 - PublicationRestrictedComment on "Influence of fochal mechanism in probabilistic seismic hazard analysis" by Vincenzo Convertito and Andre' Herrero(2006)
; ; ; ; ;Strasser, F. O.; Department of Civil & Environmental Engineering Imperial College London ;Montaldo, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Douglas, J.; BRGM, ARN/RIS ;Bommer, J. J.; Department of Civil & Environmental Engineering Imperial College London; ; ; The influence of style-of-faulting on strong groundmotions has been the subject of debate for some time. Although some controversy persists, the general consensus is that ground motions produced by reverse faults are higher than those produced by normal faults, whereas motions from strike-slip faults are somewhere in between. In a recent article, Convertito and Herrero (2004) derived a correction factor for focal mechanism to be applied to predictive equations. This issue was previously addressed by Bommer et al. (2003). Although this article is cited by Convertito and Herrero, it seems that its aims and scope were not well understood, and we would therefore like to clarify what the method presented therein entails, especially because we feel that Convertito and Herrero’s approach of characterizing focal mechanisms based solely on the radiation pattern is difficult to justify. After presenting their correction scheme, Convertito and Herrero go on to present an implementation of probabilistic seismic hazard analysis (PSHA) explicitly accounting for focal mechanism. This represents a real innovation in terms of methodology because it allows propagation of the improvements in ground-motion prediction gained through the focal-mechanism adjustments to hazard estimation. Characterizing the dominant scenario in terms of focal mechanism furthermore has the advantage of providing constraints for numerical simulations that are derived directly from the hazard computation, rather than from arbitrary assumptions. However, in our opinion, the methodology presented by Convertito and Herrero has some serious shortcomings which would need to be addressed before it can lead to improvements of the PSHA methodology. Our discussion includes a comparison with the new Italian seismic hazard map, which was derived using the Bommer et al. (2003) adjustment methodology.194 30