Come and join us at the AGS annual dinner to celebrate the success of Australian Geomechanics Society Queensland Chapter in 2015. It is the perfect time to reflect on how we have performed in the past year. The call is out for active committee members 2016 with open nominations for next year. Consider getting involved and helping make AGS QLD a greater success.
AGS Queensland is proud to announce our guest speakers for the event Chris Browitt and Alice Walker of ABConsulting, Edinburgh (previously British Geological Survey) based in the United Kingdom who will share some insights into the Earthquake history of Australia and monitoring earthquake movement.
Millimetric Ground Deformation Monitoring using Satellite Radar
Dr Chris Browitt
New ways of observing sub-millimetre ground movements using satellite radars and interferometry have created a means to better understand the impacts of active and abandoned mineral workings, fluid and gas abstraction and recharge, shrink-swell clays, compressible ground, landfill sites, landslides, volcanoes and earthquakes, as well as tunnelling, deep excavations, and even monitoring the stability of individual buildings and industrial plant.
In the 1990s, raw data collected by the European Space Agency could be used to generate interference patterns indicating, for example, how the ground was deformed by an earthquake at the cm scale. By the end of that decade, a spin-out company in Italy had invented a new processing technique which revealed ground movements at the millimetric scale. This created the capability of using such InSAR data to monitor subsidence, reservoir compaction/expansion, fault reactivation, areas of possible well failure, and calibration of geomechanical models in the groundwater, oil, gas and mining sectors. The technique has already become mature for landslide hazard determination and is widely used in Italy and Switzerland for this purpose.
Compared to conventional techniques, the InSAR approach is capable of monitoring large areas in a short period of time at low cost. It is, however, a relatively new approach that is likely to provide enhanced benefits given further experience in a wide range of applications, particularly in combination with existing ground-based monitoring and modelling techniques. It is a companion technology to them, and an explosion of new satellite radar data is imminent.
Earthquakes in “stable” tectonic environments: Australia and the UK
In Australia’s recent history, 13 people have lost their lives due to earthquakes, and in the UK’s long written history, there have been 11 documented fatalities, although half from secondary causes – eg “shock”. Both regions, however are considered to be tectonically “stable”, which actually means that the hazard is low, not that the hazard is zero. Recent seismic activity in Queensland is a testament to that. The magnitude 5.4 earthquake centred near Fraser Island on 30 July this year, whilst not damaging, caused considerable alarm and was detected on seismometers in the UK. Even at that distance, around 12,000km through the centre of the Earth, it was possible to determine the depth below the surface that the seismic energy was released. At the time of the Newcastle earthquake in New South Wales in December 1989, the seismograms we recorded in Edinburgh were the only source of information on the depth of that event (11km) owing to the lack of Australian monitoring stations at the time.
Delving further back into history, before modern instruments were deployed, to learn more about our earthquakes, we find that the biggest known in Australia had a magnitude of 7.2 and, in the UK, a magnitude of 6.1. In seismological circles, the former is considered to be large and potentially destructive (some 20 occur each year worldwide) whereas the latter is damaging (120 worldwide). Both of our countries record more than 100 earthquakes every year. However, to have a significant impact, there needs to be something in the vicinity to destroy or damage. So, the impact or risk posed by our earthquakes is determined not only by the size and frequency of them happening but also by the population density and the types of buildings exposed to the shaking.
About the Speakers
Dr Chris Browitt
Partner in ABConsulting, Edinburgh (ABC), is a geophysicist who specialised in earthquake seismology throughout most of his career. Following early retirement as Director of the British Geological Survey (Scotland), in February 2003, he formed the ABC Partnership and joined the University of Edinburgh to concentrate on interests in geohazards and disaster reduction. He continued as President of the European-Mediterranean Seismological Centre (EMSC), member of the Council of the International Seismological Centre, and Fellow of the Royal Society of Edinburgh. With the EMSC connection and as a consortium member with European Space Agency funding, he promoted and developed applications of a new, high resolution satellite radar technology (PSI), aimed at reducing geohazards and understanding ground deformation processes.
His career at the BGS Edinburgh included detailed studies of coalmining-induced seismicity, its impacts on local communities, and the discovery that the induced events closely followed the pattern of coal extraction and was influenced by previous mining activities and mine abandonment. He established the UK Seismic Monitoring and Information Service obtaining sponsorship from the mining industry, Departments of State (Energy, Environment, Education and Science) together with the Oil, Water and Nuclear industries. He completed the seismic network coverage of the UK in the 1980s and built the team of technical and scientific staff that continues to operate it today.
Ms Alice Walker
Alice Walker BSc, Partner in ABConsulting, Edinburgh (ABC), is a geophysicist specialising in earthquake seismology and seismic monitoring and hazard. She took early retirement from the British Geological Survey Edinburgh where she had participated in its Seismology Group for 30 years. During that time, she managed a 10-nation, cross-border seismicity project in Europe and, for 11 years, led the team of seismologists and technical staff on the BGS Seismic Monitoring and Information Service. The latter provided rapid details of seismic events to its sponsors, Local Authorities, the Media and Public, and conducted longer-term analysis and research to improve the service through new knowledge of the seismological characteristics of UK geology and in refinements to our understanding of seismic hazard.
In the period 1981-1994 she had a particular focus on discriminating natural earthquakes, man-made explosions and sonic booms from the fracking – induced seismic events caused by the Department of Energy’s Hot Dry Rock Geothermal project in Cornwall. Through her, the BGS acted as a “policemen” and independent arbiter in relations between the HDR project team, and the Local Authority and the Public. Over these years, she has built an international reputation including working as Officers with the European Seismological Commission and the International Association of Earthquake Seismology and Physics of the Earth’s Interior, and is renowned for her inter-personal skills. In the past three years, she has been working for the UK nuclear regulator (ONR) as a member of its Expert Panel on Seismic Hazard and Climate Change which is focused on the new build power station programme.
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