70th Sogo Bosai Seminar

  • Date : 07 Apr. 2023 15:00 - 16:30
  • Seminar
Date 07 Apr. 2023 15:00 - 16:30
Place room 301 (Collaborative Research Hub, DPRI) of Uji campus or ONLINE via zoom
Target Researcher, Student, General

We are pleased to announce the 70th Sogo Bosai Seminar (April 7) as follows. We look forward to your kind participation.
Seminar will be delivered in English.
Site amplification factors for generic to site-specific seismic hazard assessment: an overview of recent and ongoing developments in France and Europe
Dr. Pierre-Yves Bard
ISTerre (Institute of Earth Sciences), University Grenoble-Alpes, Grenoble, France
(Now a Visiting Professor of the Research Division of Disaster Management for Safe and Secure Society, DPRI, Kyoto University, Japan)
April 7, 15:00-16:30
[Venue & Registration]
Seminar will be held in the hybrid manner (virtual and face-to-face). The venue:Room 301,Collaborative Research Hub, DPRI, Uji campus, Kyoto University.
No. 77 building at the following map
Please kindly register your attendance here by April 6, noon.
Site amplification is an important component in the assessment of the expected ground motion for future earthquakes. A wide diversity of methods are presently used to account for them, with different precision and reliability levels, in principle related to the importance of the construction to be designed or retrofitted: from generic, statistics-based approaches involving only basic site information for usual buildings, to site-specific approaches (involving many variants and many on-site data) for critical facilities, with also intermediate level approaches. This talk will present an overview of investigations performed in France and neighboring countries over the last decade to (try to) improve the present state-of-practice.
Generic approaches are based on simple-to-obtain “site condition proxies” (SCPs) that are used in GMPEs (Ground Motion Prediction Equations) to associate an average site amplification factor to a given set of proxies. Those presently used in GMPEs (mostly VS30, or sometimes a site frequency for Zb depth to “bedrock”) are not sufficient, when considered as single, scalar values, to correctly describe the complexity of site amplification. A series of investigations were thus carried out, using classical statistics or AI tools, to compare not only the actual prediction performance of a collection of different proxies, and also to assess their practical easiness of use (cost, reliability, simplicity): their main outcomes will be briefly presented.
Intermediate approaches have also been proposed to assess more specifically, though still on a statistical basis, some specific components of site effects (non-linearity, underground or surface topography, …), on the basis of dedicated instrumental observations or numerical simulations. It seems reasonable to hope that such approaches could be integrated, in a not too far future in universal “Site amplification prediction equations” (SAPEs) that could be added to any regional GMPE for rock, and some tracks in that direction will be provided.
Finally, site-specific approaches may a priori include any advanced, state-of-the-art technique to assess the actual amplification at a given site with respect to the local reference rock. The recent developments in France were performed mainly in collaboration with the nuclear industry, and addressed both instrumental and numerical simulation techniques. The former use in-situ earthquake and/or ambient vibration recordings, in particular the “hybrid standard spectral ratio technique” (SSRh): the main achievement has been to show their feasibility and usefulness even in French-like, moderate seismicity areas. The latter seem very appealing because of the impressive growth of computer power and the never-ending improvement of numerical codes. It was however decided to focus the investigations on the assessment of their effective reliability through dedicated benchmarking experiments involving international teams (underground geometry effects in the linear domain, non-linear 1D site response, non-invasive site survey techniques): their results, although encouraging, invite to modesty, partly because of the difficulty to measure all the required parameters. In addition, as local reference sites very often correspond to hard to very rock, a special attention was devoted to the estimation of ground motion for such sites, for which only very few direct recordings are available; their results yield very different results compared to the classical “host-to-target” adjustment techniques based on VS30 and the “kappa” parameter.
[Short bio]
Dr. Pierre-Yves Bard is a world-renowned researcher with numerous accomplishments in the fields of seismology and earthquake engineering, particularly in the prediction of strong ground motions and the evaluation of site amplification characteristics important for that purpose. He graduated from the Ecole Nationale des Ponts et Chaussées, Paris, in 1976 and received his Bachelor of Civil Engineering diploma in 1978. Then he worked as an engineer in the Ministry of Equipment, with a fellowship program for doctorate studies in the Laboratory of Science of the Earth’s Interior (LGIT), Grenoble. He received his Doctorat ès Sciences Physiques from the Joseph Fourier University in Grenoble in 1983. He then continued to work as a researcher in LGIT, which was reformed later as the Insitut des Sciences de la Terre (ISTerre), from 1984 up to the present. During that time, he also held a concurrent appointment at the National Institute of Civil Engineering, Planning, and Networks (IFSTTAR), where he helped to bridge the perception gap between seismologists and earthquake engineers.
Dr. Bard’s primary research interests are in strong-motion seismic hazard prediction and the resulting seismic hazard assessment. He has conducted a wide range of research, with a particular focus on all types of site amplification effects related to near-surface heterogeneity, including dynamic ground-structure interactions. In particular, he and his team have done excellent works on the characterization and application of microtremor measurements, unraveling many of the mysteries that Japanese researchers have obscured. Dr. Bard has authored 159 peer-reviewed papers, 18 other papers, 28 book chapters, 48 invited papers for international conferences, and 185 conference papers by 2020. In 2006, he organized the third International Symposium on the Effects of Surface Geology on Strong Ground Motions (ESG) in the University of Grenoble and conducted blind prediction experiments using microtremor analysis methods, which were very well received.