The EQRM is Geoscience Australia's tool for conducting probabilistic seismic hazard and risk assessments. In this report we summarise the sensitivity of EQRM risk estimates to a range of input parameters. The importance of aleatory uncertainity is explored separately for the following components of the EQRM: synthetic earthquake catalogue generation, attenuation, regolith amplification and damage modelling. Different sampling techniques are analysed for incorporating aleatory uncertainty. Event and hazard based approaches to risk estimation are compared. Finally, we demonstrate the impact of using different attenuation models on risk estimates.

In order to calibrate earthquake loss models for the U.S. Geological Survey's Prompt Assessment of Global Earthquakes for Response (PAGER) system, two databases have been developed: an Atlas of ShakeMaps and a catalog of human population exposures to moderate to strong ground shaking (EXPO-CAT). The full ShakeMap Atlas currently contains over 5,600 earthquakes from January 1973 through December 2007, with almost 500 of these maps constrained by instrumental ground motions, macroseismic intensity data, community internet intensity observations, and published earthquake rupture models. The catalog of human exposures is derived using current PAGER methodologies. Exposure to discrete levels of shaking intensity is obtained by merging Atlas ShakeMaps with a global population database. Combining this population exposure dataset with historical earthquake loss data provides a useful resource for calibrating loss methodologies against a systematically-derived set of ShakeMap hazard outputs. Two applications of EXPO-CAT are illustrated: i) a simple objective ranking of country vulnerability to earthquakes, and; ii) the influence of time-of-day on earthquake mortality. In general, we observe that countries in similar geographic regions with similar construction practices tend to cluster spatially in terms of relative vulnerability. We find only limited quantitative evidence to suggest that time-of-day is a significant factor in earthquake mortality. Finally, we combine all the Atlas ShakeMaps to produce a global map of the peak ground acceleration (PGA) observed in the past 35 years, and compare this composite ShakeMap with existing global hazard models. In general, these analyses suggest that existing global and regional hazard maps tend to overestimate hazard.

Earthquakes are not uncommon in Australia and are occasionally a threat to life and property as so tragically demonstrated by the Newcastle earthquake. This report 411contains information on earthquakes of Richter magnitude 3 or greater that were reported in the Australian region during 1991. An annual report has been compiled since 1980 by the Australian Geological Survey Organisation (AGSO), using data from AGSOand contributing seismological agencies in Australia. Its purposes are to aid the study of earthquake risk in Australia, and to provide information on Australian and world earthquakes for scientists, engineers and the general public. The report has six main sections: Australian region earthquakes; Isoseismal maps; Network operations; Accelerograph data; Principal world earthquakes; and Monitoring of nuclear explosions.

The report summarises earthquake and tsunami information worldwide in 1997 but with a focus on Australia for use by scientists, engineers and the public. Maps of the seismicity are presented on a state-by-state basis and isoseismal maps are included for the significant earthquakes.

Continental Australia is characterised overall by relatively high levels of seismic activity in comparison with intracratonic areas worldwide. However, the link between earthquake events and earthquake-related geomorphology in Australia remains poorly understood for all except the largest events, because landscape impact unambiguously attributable to seismic activity is typically difficult to recognise. In this context, we describe several unusual fracture systems of possible tectonic origin that transect granite pavements in the Archaean eastern Pilbara Craton of Western Australia. Occurring at four localities (Gallery Hill, North Shaw, Mulgandinnah Hill and Muccan) separated by up to 150 km, the fracture systems typically range up to 100 m in length and 20 m in width, locally offset pavement surfaces by up to 15 cm vertically, and expose uniformly fresh-looking rock. At one locality (Muccan), the fractures directly crosscut two generations of aboriginal petroglyphs etched into the pavement surface, which suggests that fracture formation occurred relatively recently, and probably quite rapidly. All four localities are characterised by extensional structures (tension fractures and dilated joints) striking 020?040?, and three preserve compressional structures (steeply-dipping reverse faults at Gallery Hill and North Shaw, A-tent crestal fractures at Mulgandinnah Hill) trending 100?135?. These strongly correlated alignments militate against an origin controlled purely by weathering-related phenomena, and the observed pattern is compatible with the formation of all documented fracture systems within a single East Pilbara-wide stress field, dominated by pure shear and characterised by NE?SW to NNE?SSW directed maximum horizontal compression. This orientation is consistent with that derived via spatial averaging of the stress orientation data available from northwestern Australia. The results are preliminary, but have exciting implications for: (1) inexpensive field-based determination of regional stress orientation, and (2) probabilistic seismic hazard assessment and the identification of earthquake-prone regions using granitic landforms.

The Mw 7.1 New Zealand earthquake was the largest earthquake in New Zealand in 60 years and occurred in the sparsely populated Fiordland region of New Zealand. The earthquake caused no deaths and only minor damage in the town of Te Anau, although it was felt through out most of the south island of New Zealand. Surprisingly, it was felt in Sydney, 1800 kilometre away, with some people evacuating buildings. People in Sydney did not feel body or surface waves but felt the T phase from the event. Human perception of a T phase is very rare, with the 1977 Mw8.1 Tonga event being felt in Tahiti 2600 km away (Talandier and Okal 1979), being one of the few well documented instances. The Sydney recording of T phase, whilst larger than the body waves, would still be considered weak motion and not normally felt. I suggest that for someone to have felt this event required the coincident of several factors which enhanced the resulting shaking.

Seismicity in the Australian region in 1989 was about average and the largest earthquake was that at Newcastle, which at magnitude ML 5.6, is the modal or most frequent annual maximum magnitude for mainland Australia. Another earthquake near Mt Olga, Northern Territory on 28 May had a similar size but their effects were dramatically different. Few people even felt the Mt Olga earthquake and only minor damage was reported by national park rangers at the tourist centre. The earthquake at Newcastle highlighted the difference between earthquake hazard and earthquake risk.

A moderate-sized earthquake (Ms 5.8) earthquake on 30 March 1986 was associated with surface rupture near Marryat Creek in northernmost South Australia, 300 krn southwest of Alice Springs. The fault scarp is shaped like a chevron that points toward the northeast. The north-south limb of the scarp is about 7.5 km long, and the WSW-ENE limb is 5.5 km long. Results of detailed surveying of the fault scarp give the shape and vertical displacement of the scarp at points along its full length.

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This report contains information on earthquakes of Richter magnitude 3 or greater that were reported in the Australian region during 1990. It is the eleventh of an annual series compiled by the Australian Geological Survey Organisation (AGSO), using data from AGSO and various seismological agencies in Australia. Its purposes are to aid the study of earthquake risk in Australia, and to provide information on Australian and world earthquakes for scientists, engineers and the general public. The report has six main sections: Australian region earthquakes; Isoseismal maps; Network operations; Accelerograph data; Principal world earthquakes; and Monitoring of nuclear explosions.