Design earthquake ground motion prediction for Perth metropolitan area with microtremor measurements for site characterization

Perth is the largest city in Western Australia and home to three-quarters of the state's residents. In recent decades, there have been a lot of earthquake activities just east of Perth in an area known as the South-West Seismic Zone. Previous numerical results of site response analyses based on limited available geology information for PMA indicated that Perth Basin might amplify the bedrock motion by more than 10 times at some frequencies and at some sites. Hence, more detailed studies on site characterization and amplification are necessary. The microtremor method using spatial autocorrelation (SPAC) processing is a useful tool for gaining thickness and shear wave velocity (SWV) of sediments and has been adopted in many previous studies. In this study, the response spectrum of rock site corresponding to the 475-year return period for PMA is defined according to the probabilistic seismic hazard analysis (PSHA) based on the latest ground motion attenuation model of Southwest Western Australia. Site characterization in PMA is performed using two microtremor measurements, namely SPAC technique and H/V method. The clonal selection algorithm (CSA) is introduced to perform direct inversion of SPAC curves to determine the soil profiles of representative PMA sites investigated in this study. Using the simulated bedrock motion as input, the responses of the soil sites are estimated using numerical method based on the shear-wave velocity vs. depth profiles determined from the SPAC technique. The response spectrum of the earthquake ground motion on surface of each site is derived from the numerical results of the site response analysis, and compared with the respective design spectrum defined in the Australian Earthquake Loading Code. The comparison shows that the code spectra are conservative in the short period range, but may slightly underestimate the response spectrum at some long period range.

Disquiet on the research front : surveying the battle ground between researchers and human research ethics committees

In this paper, I play with the metaphors of war and peace (with apologies to Leo Tolstoy) as a strategy for describing the relations between (some) social science researchers and human research ethics committees. Even a cursory survey of recent literature reveals a raft of grievances and grumblings amongst researchers about the operation and decisions of research ethics committees. This paper presents a partial survey from both sides of some of the claims that have triggered this unofficial declaration of war, and discusses the implications for ethical research. My central argument is that the truly ethical moment lies in mutual and constructive conversations and critique between ethics committees and researchers.

Above- and below-ground vertebrate herbivory may each favour a different subordinate species in an aquatic plant community

At least two distinct trade-offs are thought to facilitate higher diversity in productive plant communities under herbivory. Higher investment in defence and enhanced colonization potential may both correlate with decreased competitive ability in plants. Herbivory may thus promote coexistence of plant species exhibiting divergent life history strategies. How different seasonally tied herbivore assemblages simultaneously affect plant community composition and diversity is, however, largely unknown. Two contrasting types of herbivory can be distinguished in the aquatic vegetation of the shallow lake Lauwersmeer. In summer, predominantly above-ground tissues are eaten, whereas in winter, waterfowl forage on below-ground plant propagules. In a 4-year exclosure study we experimentally separated above-ground herbivory by waterfowl and large fish in summer from below-ground herbivory by Bewick’s swans in winter. We measured the individual and combined effects of both herbivory periods on the composition of the three-species aquatic plant community. Herbivory effect sizes varied considerably from year to year. In 2 years herbivore exclusion in summer reinforced dominance of Potamogeton pectinatus with a concomitant decrease in Potamogeton pusillus, whereas no strong, unequivocal effect was observed in the other 2 years. Winter exclusion, on the other hand, had a negative effect on Zannichellia palustris, but the effect size differed considerably between years. We suggest that the colonization ability of Z. palustris may have enabled this species to be more abundant after reduction of P. pectinatus tuber densities by swans. Evenness decreased due to herbivore exclusion in summer. We conclude that seasonally tied above- and below-ground herbivory may each stimulate different components of a macrophyte community as they each favoured a different subordinate plant species.

Ground truthing : explorations in a creative region

Australia’s evocative Mallee region is rich with histories, impressions and geographical complexities. It is also a microcosm of a world in turmoil.

Ground Truthing allows the Mallee to speak: to show its nurturing and renewable self. In searching for the creative principles that bring the Mallee into being, Carter digs, plots and weaves a poetic passage. A Wotjobaluk man, 'Jowley', the poet John Shaw Neilson and pastoralist William Stanbridge are among characters that give creative access to the region. Their voices mingle with those of vanished peoples and an ecological future crying out for renegotiation.

Through this spatial history of the Mallee, we see that regions contain 'the region of regions' that is the creative key to the production and sustenance of all places.

Cost factors affecting the design of ground-supported floors

The cost of concrete ground-supported floor slabs represents a significant proportion of the total capital cost of industrial projects. There are many structural design issues that impact on the concrete contractors’ method of construction. This is becoming more apparent with the use of new high-technology levelling and trowelling equipment, which has significantly increased the pour and finishing rates, resulting in much faster slab construction times compared with the traditional methods of construction. Selection of both the design and the construction methods exerts a large influence on the initial cost. According to the results of the research reported in this paper, it may be possible to save between 2-4 per cent of the building cost if high technology solutions are incorporated into the design and construction process. This paper investigates cost issues that impact on the design and construction of ground-supported floors for industrial buildings.

Shifting ground in some Australian photography

This is a report of a practice-as-research project. The chapter outlines McArdle's discoveries of means by which the pre-conscious processes of binocular vision and steropsis can be made visible in an effect which with one-eyed vision renders the scene 3-dimensional.

In the book's introduction editor Mehigan writes "[The] will to creation is only assayable once we estimate the role of the observer in the construction of space. McArdle's contribution, in engaging with the question of the animating presence of the observer focuses not just on what is caught in the lens of the photographer at the moment of depiction, but how the photographer's movement through space is the 'force field' that insinuates itself into the landscape and enters into a reciprocal relationship with it. The schematism of Euclidean geometry, for this reason, cannot account for the truth of the photographer's images; McArdle's metaphors are singularly non-Euclidean in their description of how objects are held together in the imaginative space of mental awareness."

Double horizons : shifting figure and ground in some Australian photography

How many of Australia's ground-nesting birds are likely to be at risk from the invasive Cane Toad (Rhinella marina)?

Cane Toads (Rhinella marina; hereafter 'toads') are large, toxic American anurans that were introduced to Australia in 1935. Research on their ecological impact has focussed on the lethal ingestion of toxic toads by native frog-eating predators. Less attention has been paid to the potential impacts of Cane Toads as predators, although these large anurans sometimes eat vertebrates, such as nestling birds and bird eggs. We review published and unpublished data on interactions between Cane Toads and Australian ground-nesting birds, and collate distributional and breeding information to identify the avian taxa potentially at risk of having eggs or chicks eaten by Cane Toads. Cane Toads are currently sympatric with 80 ground-nesting bird species in Australia, and five additional species of bird occur within the predicted future range of the toad. Although many species of bird are potentially at risk, available data suggest there is minimal impact of Cane Toads on ground-nesting species. Future research could usefully address both direct and indirect impacts of the invasion by Cane Toads, ideally with detailed field observations of these impacts on nesting success and of changes in bird breeding success as a function of invasion by toads.