Borehole seismometer installation at Bradwell B for enhanced earthquake detection and site characterisation for seismic hazard assessment

Synopsis

Earthquake recordings are of great benefit to support site-specific seismic hazard assessments for critical infrastructure but can also bring broader benefits when the seismometer installations are integrated into the wider national seismic monitoring network.  This presentation describes the planning, deployment and operation of a string of seismic sensors in a single borehole at the proposed Bradwell B nuclear power station site in November 2018 and how the data captured has been used to enhance earthquake detection as part of the BGS national seismic network and for site characterisation for a probabilistic seismic hazard analysis (PSHA) undertaken by Jacobs.

In the first part of the talk, Iain Tromans (Jacobs) sets out the benefits of on-site earthquake monitoring for nuclear facilities, with reference to regulatory guidelines from IAEA and ONR, focusing on the reduction of uncertainties in the inputs to PSHA. 

David Hawthorn (BGS) covers the technical and logistical aspects of the deployment and operation of the Bradwell borehole seismometer array, as well as integration with the wider national seismic monitoring network. Such integration enhances local earthquake detection as well as helping with the operation and validation of the monitoring station itself. The potential future use of the monitoring equipment, and others like it, are also examined in terms of their benefits over the operation life of a nuclear facility. 

Angeliki Lessi-Cheimariou presents how weak-motion records collected over an 18-month period were used in the development of various aspects of the PSHA model, including the spectral decay parameter, kappa, the vertical/horizontal (V/H) response spectral ratios and site amplification. Angeliki will focus on how use of site-specific weak-motion data helped reduce the uncertainties associated with the site’s eigenfrequencies, ultimately providing greater confidence in the modelling of site-effects within the PSHA.

About the speakers

Dr Iain Tromans' career in earthquake engineering began with a PhD at Imperial College, investigating factors influencing the distribution of damage to buried infrastructure, based on fieldwork following the devastating earthquakes in Turkey in 1999. Iain has spent the past 22 years in engineering consultancy, being heavily involved in seismic hazard assessments for critical infrastructure, with a particular emphasis on nuclear facilities. Dr Tromans was closely involved in all aspects of the delivery of site-specific PSHAs at Hinkley Point C, Sizewell C and Bradwell B, as the lead of the Technical Integration team. As Head of Technology for Seismic Geotechnics at Jacobs, Dr Tromans provides technical leadership in the development and application of novel solutions in geotechnical earthquake engineering and engineering seismology for clients spanning the energy, defence, transportation, maritime, water and urban sectors.

Dr David Hawthorn is a Seismologist with the British Geological Survey. His current work is strongly focused on the management of the UKs permanent national network of around 70 seismic monitoring stations, as well as smaller temporary networks deployed to achieve more specific goals (baseline seismicity surveys, enhanced detection thresholds etc.). His work also involves operating several site-specific seismic stations at nuclear licensed sites and dams, which are integrated with the wider seismic network. He has been working in the field of passive seismology since 2007 for both academic and governmental organisations. His work has included aftershock studies following large damaging earthquakes (Indonesia in 2008, Chile in 2010 and Indonesia in 2018), tracking volcanic activity in Iceland, monitoring Hydraulic fracturing of shale gas in Lancashire (2018) and earthquake swarms in Surrey (2019).

Dr Angeliki Lessi-Cheimariou is a senior earthquake engineering specialist with over sixteen years of experience in site response analysis and site characterisation. She led these aspects for the site-specific probabilistic seismic hazard analyses undertaken by Jacobs for major nuclear infrastructure projects, including Hinkley Point C, Sizewell C, and Bradwell B. Her expertise extends across the broader geotechnical and earthquake engineering fields. Throughout her professional career she has made use of innovative approaches in site response analysis which were originally explored during her PhD at Imperial College London, and which have helped provide robust, safety-critical solutions for large-scale infrastructure.

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Further information

This event is organised by SECED, and chaired by Dr Guillermo Aldama-Bustos (Jacobs). The event is open to all and is free to attend.