@article {bnh-8215, title = {Cost-effective mitigation strategy development for building related earthquake risk {\textendash} Melbourne case study}, number = {707}, year = {2021}, month = {09/2021}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Earthquake hazard was not fully recognised in Australian building design until the mid-1990{\textquoteright}s. This oversight has resulted in a legacy of vulnerable buildings that can be readily damaged in moderate to severe Australian earthquakes. In particular, older unreinforced masonry (URM) buildings built with the architectural styles, materials and construction details used in the United Kingdom are particularly vulnerable. Australian earthquakes have highlighted the vulnerability of this building type. These events include the Adelaide Earthquake of 1954, the Meckering Earthquake of 1968, the Newcastle Earthquake of 1989 and the Kalgoorlie Earthquake of 2010, all of which damaged pre WWII masonry buildings in particular.\  Buildings of this style are present in the older centres of our major cities, and Melbourne has a very significant number of these. As shown in this research, in number nearly half of the buildings in the Melbourne central business district are of this type of construction. The damage to these buildings can greatly add to human casualties as a result of falling masonry elements. Further, the severity of damage and losses can impede the recovery of cities like Melbourne physically, economically and socially. Finally, many of these buildings have heritage value to communities that residents may want preserved.

This document reports on the final deliverable for Project A9 Cost-effective mitigation strategy development for building related earthquake risk of the Bushfire and Natural Hazards Collaborative Research Centre (CRC). It builds on the masonry component research of the University of Adelaide in this project and is a milestone for Geoscience Australia. The work follows the utilisation project entitled {\textquotedblleft}Earthquake Mitigation of WA Regional Towns: York Case Study{\textquotedblright}, that was jointly delivered by GA and the University of Adelaide. The utilisation project developed original condition and mitigated vulnerability models for six URM building types. In this project, these outcomes have been applied to the much larger Melbourne CBD exposure.

The project had the following key components:

The work required the development of the three fundamental risk elements of earthquake hazard, community exposure and building vulnerability. It also entailed the assessment of the economic loss measures associated with human injury, contents losses, rental income, commercial property leasing, and business activity. Additionally, it included the application of the semi-intangible value placed on human life to society. Each of these are described below.

Earthquake hazard

This study has drawn upon the latest understanding of the Melbourne region earthquake hazard by utilising the recently released National Seismic Hazard Assessment (NSHA 2018) (Allen et al, 2018a). The bedrock hazard from this assessment shows Melbourne to have a {\textquotedblleft}low{\textquotedblright} earthquake hazard by global standards but significant by Australian standards. The hazard is further amplified by the presence of the sediments deposited by the Yarra River.\  These soil effects increase the hazard, particularly those in the study region south of the Yarra River. The effects of soil amplification can double the severity of shaking in some areas.

Community exposure

The definition of the building assets in the study region utilised several sources. The available state government building data integrated into the National Exposure Information System (NEXIS) was accessed and supplemented by an engineering survey database developed and maintained by GA for the Australian Reinsurance Pool Corporation. This was further refined by a desktop review of all masonry buildings utilising available street level imagery. In total there were 1,543 buildings in the study region, and 687 of these were identified as URM.

The assessment of human activity was achieved by utilising research undertaken outside of this project. This research utilised a population model developed by downscaling a destination zone based telecommunication model with pedestrian counts, the Melbourne traffic control systems movement counts, and building floor area information. Using this work it was possible to define the local human exposure at the time of the scenario event, particularly those in damaged buildings and those potentially exposed to falling masonry during a rapid onset earthquake event.

Building vulnerability

The building vulnerability assessment work for the URM building stock was a direct utilisation of the six vulnerability types identified in the earlier York WA mitigation study. This included the vulnerability in present condition, and that with mitigation measures applied to the vulnerable elements. To complete the context, the vulnerability of other building types was attributed using a suite of models developed through an adaptation of US HAZUS models, reference to \ heuristically developed models from a GA facilitated UN workshop (Maqsood et al, 2014), and through heuristic adjustments by the project team. This vulnerability of non-URM buildings remained a constant in the study as mitigation of these buildings was not considered.

Economics of cost assessment

The economic assessment considered a broad range of measures. These ranged from the direct costs to property owner, building occupiers, and businesses through to health care costs and the partially intangible value placed on the loss of a human life. The aim was to provide scalable information on benefits versus cost to a range of decision makers and investors. Importantly, the measures where not comprehensive and so represent a lower bound to the actual avoided impacts mitigation achieves. For example, the cost of emergency response, clean-up and community recovery support were not considered. Neither was a macro-economic perspective developed to capture non-impacted businesses that would benefit from a stimulus in business activity such as in the construction industry, the supply of home appliances, soft furnishings and drapery. Significantly, the value of avoided heritage building loss was considered through the utilisation of metrics developed by a UWA led CRC project.

Scenario impacts and risks

The study considered a single rare earthquake scenario having an annual likelihood of 1/5,000 of causing the targeted bedrock shaking severity beneath the Melbourne CBD, or greater. This likelihoods corresponds with a 1\%, chance of this shaking severity being exceeded in the next 50 years. For the event the injuries and other losses within the scope of this study were assessed using the human exposure corresponding with 11:00am of Monday through to Thursday. The losses ranged from $737m for building damage only, through to $1.66b for the other monetary costs considered.\  The value of human life lost increased this to $3.97b. Where 25\% of the masonry building stock was retrofitted, over 30 years, these losses reduced by approximately 16\%.

The reduction in injuries if this event occurred in 30 years time was also evaluated. Serious injuries reduced by 16 and deaths by 98 persons. Urban Search and Rescue logistics would also reduce correspondingly.

In a similar manner, the long term financial risk of the Melbourne CBD study region was evaluated for building damage. It was presented as the average annualised loss for the URM building stock and for the entire study region buildings. It was also forecast 30 years into the future and the financial risk reduced by 38\% for the URM building stock and by 10\% across the entire study region buildings.

Discussion and outcomes

Earthquakes occur frequently in Australia with over 100 events greater than magnitude 3.0 (ML) recorded within the Australian continent every year by Geoscience Australia. The smaller and more frequent events are typically non-damaging, whereas the less frequent larger events can be very damaging when they occur close to a community. This plays out in the economics of strengthening older structures where the benefits of avoided building damage and contents losses through retrofit for earthquake are not a full offset for the significant costs.\  Other avoided costs associated with business losses, lost wages, health care costs, and the value placed on human life, do increase the sum significantly but are not realised by the property owner. While not all avoided costs were considered, this project indicates that the justification for retrofit based solely on a financial investment may be difficult to demonstrate for URM buildings in Melbourne.

As was also illustrated by the earlier York study, there are other considerations for the retrofit of URM buildings in the Melbourne CBD and in other older business districts in the city. If a rare earthquake occurred locally during a period of high public exposure there would be considerable loss of life. This research has shown that if a 5,000 year Return Period (RP) event (5.5 Mw) occurring on a business day approximately 100 people would die with close parallels to the 2011 Christchurch Earthquake outcome for masonry structures (42 fatalities). This may point to cheaper levels of retrofit with the objective of tying back elements that could cause casualties, rather than having the aim of avoiding economic loss.

Further, following a rare, but credible, earthquake high value heritage buildings would be lost. The research has shown that the willingness to pay by just the residents of the City of Melbourne LGA adds a notional 10\% of the total benefits of the mitigation program.

SUMMARY

The project has applied a range of retrofit measures for a suite of six URM building types developed as part of Project A9 to a very large population of URM building found in the Melbourne CBD. These measures have been demonstrated to reduce the physical vulnerability of each building. The project has also translated this vulnerability change into broader metrics that form an evidence base to inform decisions to retrofit.

The project has also demonstrated the benefit of retrofit through a virtual retrofit of a major city CBD. These benefits include reduced post event logistics for emergency management and the local government, reducing financial losses to building owners, businesses, and reducing injuries and fatalities. It has also demonstrated that retrofit reduces the long term financial cost of earthquake hazard, thereby making risk transfer through insurance uptake more affordable. Finally, it has demonstrated how valuable heritage structures can be progressively preserved for the future by protecting them from future credible earthquakes.

}, keywords = {buildings, earthquake, Melbourne, mitigation, risk, strategy}, issn = {707}, author = {Hyeuk Ryu and Martin Wehner and Jaroslav Vaculik and Valdis Juskevics and Mark Edwards and Michael Griffith and Itismita Mohanty and Stuart Butt and Neil Corby and Trevor Allen and Robert Hewison} } @article {bnh-7186, title = {Earthquake mitigation of WA regional towns: York case study - final report}, number = {596}, year = {2020}, month = {08/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {MELBOURNE}, abstract = {

Earthquake hazard was only fully recognised for Australian building design in the early 1990{\textquoteright}s following the Newcastle Earthquake of 1989. This has resulted in a significant legacy of Australian buildings that are inherently more vulnerable to low to moderate earthquake generated ground motion. Having accessible knowledge of the most effective measures to retrofit older masonry buildings will enable and encourage the strengthening of buildings resulting in more resilient communities.

Western Australia has a region of elevated seismicity inland from Perth where there are located several older regional towns having a predominance of older unreinforced masonry (URM) buildings. In 1968 the town of Meckering was devastated by an earthquake (Gordon et al, 1980), which destroyed the town{\textquoteright}s URM building stock and damaged URM buildings in other neighbouring towns. The town of York, situated approximately 37km from the epicentre was also significantly damaged (Everingham et al, 1982). The combination of high hazard and vulnerability in this region points to a need for informed mitigation measures.

This project entailed undertaking a mitigation implementation study of York, Western Australia{\textquoteright}s oldest inland town, which has many valuable historical buildings that are vulnerable to damage by a large earthquake. This utilisation project sits beneath and draws upon the vulnerability and economic modelling research outcomes of the BNHCRC project {\textquotedblleft}Cost-effective Mitigation Strategy Development for Building related Earthquake Risk{\textquotedblright}. Utilising the outcomes of the project a range of mitigation strategies have been virtually applied to the town{\textquoteright}s URM buildings. This has enabled an assessment of the effectiveness of these interventions on community risk and emergency management (EM) logistics in the context of rare, but credible, earthquakes.

In this report the research and its outcomes are presented and discussed. Further, recommendations are made for future retrofit strategy implementation in York and more broadly in Western Australia. In particular, a new NDRP project is described that will build upon this BNHCRC project in testing the application of the measures in actual retrofit work undertaken in York. This BNHCRC project has been led by the University of Adelaide (UoA) with project partner Geoscience Australia (GA). The end users are the Shire of York and the WA Department of Fire and Emergency Services (DFES) with valuable contributions made by the WA Department of Planning, Lands and Heritage. Through the workshop activity reported there have also been valuable guidance from Engineering Heritage, WA, and the Insurance Australia Group (IAG).

}, keywords = {earthquake, mitigation, regional towns, york}, issn = {596}, author = {Martin Wehner and Hyeuk Ryu and Michael Griffith and Mark Edwards and Neil Corby and Itismita Mohanty and Jaroslav Vaculik and Trevor Allen} } @conference {bnh-6385, title = {Earthquake Management Logistics for York, WA, Pre and Post Mitigation}, booktitle = {Australian Earthquake Engineering Society 2019 Conference}, year = {2019}, month = {12/2019}, address = {Newcastle}, abstract = {

Rare Australian earthquake events can cause extensive damage and present significant logistical challenges for emergency management agencies and local governments. Evidence of this can be seen from recent earthquake events that include the 2010 Kalgoorlie earthquake and the 1989 Newcastle earthquake of 30 years ago. Emergency managers do not experience damaging earthquakes on the same regular basis as storms, floods, and bushfires and therefore don{\textquoteright}t always fully understand the consequences they may face. Scenario modelling can provide insights to inform response and recovery by emergency management and recovery agencies as well as demonstrate how these impacts can be moderated by the retrofit of the most vulnerable building types.

The Shire of York is partnering with the WA Department of Fire and Emergency Services (DFES), the University of Adelaide and Geoscience Australia in a collaborative project that explores the current earthquake risk in the heritage town of York, Western Australia, and how the risk could be moderated through targeted retrofit. The project forms part of the Bushfire and Natural Hazards Cooperative Research Centre project {\textquotedblleft}Cost-effective Mitigation Strategy Development for Building Related Earthquake Risk{\textquotedblright}. This paper describes the approach taken and the predicted consequences modelled for a range of credible earthquake scenarios. Significantly, based on the recommendations from a stakeholder workshop in York on the 9thAugust 2018, it is also assessing how these consequences would be moderated in future decades through two rates of retrofit uptake in the town. This work is informing emergency management planning by DFES and the Shire of York. It is also illustrating the benefits of targeted community level retrofit to address the risk posed by the community building types most vulnerable to earthquakes.

}, keywords = {earthquake, Emergency management, modelling, retrofit, senario}, url = {https://aees.org.au/wp-content/uploads/2019/12/70-Hyeuk-Ryu.pdf}, author = {Hyeuk Ryu and Mark Edwards and Martin Wehner and Stephen Gray and Michael Griffith and Jaroslav Vaculik and Neil Corby and Trevor Allen} } @conference {bnh-6027, title = {Mitigating earthquake risk in Australia}, booktitle = {2019 Pacific Conference on Earthquake Engineering and Annual NZSEE Conference}, year = {2019}, month = {09/2019}, abstract = {

Earthquake risk is not limited to tectonic plate boundary countries. While less frequent, significant earthquakes can occur in intraplate countries like Australia which can have severe consequences. For Australia this is particularly the case as earthquake hazard has not been recognised in the design of buildings and community infrastructure for most of the country{\textquoteright}s settled history. Significant risks exist where community assets are by their nature inherently vulnerable to strong ground shaking. This paper describes three initiatives that are assisting Australian emergency management, infrastructure managers and local government to prepare for and mitigate these risks.

The first of these highlights how the characteristics of geological hazards differ from severe meteorological hazards. The very non-linear nature of impact severity with longer average recurrence interval earthquakes is demonstrated and how this information is supporting emergency management planning including capacity sharing between Association of Southeast Asian Nations (ASEAN) countries in the region is described. Secondly, the paper describes how this research is developing knowledge of the factors behind the vulnerability of critical infrastructure facilities and the options to mitigate these. The software tool System for Infrastructure Facility Resilience Analysis (SIFRA) is described which enables infrastructure facility components to be examined in the context of physical vulnerability, system criticality, repair cost and restoration time. Finally, a utilisation project of the Bushfire and Natural Hazards CRC working with the local government of York Shire in Western Australia (WA) is described. The project is providing information on the effectiveness of targeted retrofit of the heritage town of York to rare earthquakes and how this action by property owners can be incentivised.

}, keywords = {earthquake, mitigation, Vulnerability}, url = {http://db.nzsee.org.nz/2019/Oral/8C.05\%20Edwards.pdf}, author = {Mark Edwards and Muhamman Rahman and Hyeuk Ryu and Martin Wehner and Neil Corby and Michael Griffith and Jaroslav Vaculik} } @article {bnh-3861, title = {Launceston flood risk mitigation assessment - June 2016 floods: suburb of Newstead}, number = {339}, year = {2017}, month = {10/2017}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Launceston is floodprone and located within the Tamar River floodplain at the confluence of the Tamar, North Esk and South Esk Rivers in Tasmania. Launceston has been subjected to 35 significant floods since records began, with the 1929 flood considered to be the worst (Fullard, 2013). A new Launceston Flood Authority was established in 2008 to design, construct and maintain existing and new flood levees. To replace the existing deteriorated levees a flood mitigation initiative was completed in 2016 to provide Launceston with reliable flood protection up to the 200 year Annual Recurrence Interval (ARI) event (Fullard, 2013).

However, this flood mitigation initiative did not extend to Newstead, a suburb in the east of Launceston, with the suburb consequently not protected from floods. Therefore, a new levee was proposed to protect the properties in Newstead from future floods. The cost of the proposed levee was estimated to be $580,000 along with an annual maintenance cost of $10,000 (Fullard, 2016).

Geoscience Australia was funded to undertake a project to conduct a Cost Benefit Analysis (CBA) of the proposed flood levee in Newstead as a variation to its current project (BNHCRC, 2017a) within the Bushfire and Natural Hazards CRC (BNHCRC). The project stakeholders included the CRC, Tasmanian Department of Premier and Cabinet, Tasmanian State Emergency Service, the City of Launceston, Launceston Flood Authority and Northern Midlands Council.

This report provides the details of the CBA of the proposed flood levee along with consideration of several other mitigation options as researched within the BNHCRC flood mitigation project.

}, isbn = {978-0-9941696-8-6}, issn = {339}, author = {Maqsood, T and Martin Wehner and Itismita Mohanty and Neil Corby and Mark Edwards and Fiona L Gibson and Rogers, Michael J.} } @article {bnh-3803, title = {Launceston flood risk mitigation - June 2016 floods}, number = {257}, year = {2017}, month = {10/2017}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

With Launceston experiencing severe flooding in June 2016, this project reviewed the costs and benefits of mitigation work (upgraded levees) which began in 2010. Flood mitigation is an expensive exercise, and this research highlights the benefits through avoided impacts of the flood levee mitigation program, against the cost of construction.

Findings show that the upgrading of the levee system, completed in 2014, resulted in avoiding losses of about $216 million (had the pre-existing levees failed), which is approximately four times the total investment in the new levee system. This investment in building the new levee system was found to be a sound economic decision based on the estimated costs at the time of decision making, alongside improved estimates of benefits from this study. The actual benefits of these mitigation works to the community extend beyond the direct benefits as assessed in this project, to the intangible and indirect benefits that have not been included.

It was found that sea level rise scenarios would only have a limited impact on building losses. However, the combined impact of sea level rise and increased rainfall intensity due to climate change on the total losses may be significantly greater and could be further investigated.

The study assessed:

}, isbn = {978-0-9941696-7-9}, issn = {257}, author = {Maqsood, T and Martin Wehner and Itismita Mohanty and Neil Corby and Mark Edwards} }