December 2004

• Enormous earthquake in Indonesia causes tsunami
• A new standard in geological data
• Geoscience Australia Christmas shut-down period
• Annual Report on Mineral Resources

In the nine hours following the enormous earthquake off Sumatra, 14 aftershocks with magnitudes between 5.7 and 7.3 occurred along the arc from Sumatra towards Nicobar and Andaman Islands.

The string of seismic events began when an enormous earthquake occurred off the West coast of Sumatra today (26 December 2004) at 11:59am AEDST (0.58 UT). It measured magnitude 9.

The epicentre was approximately 320 km west of Medan, Sumatra. This earthquake was the result of plate collision, caused by the Australian plate moving northwards about 7cm per year.

"This is the largest earthquake in the world for forty years, and the fifth largest in the world since 1900," said Dr Cvetan Sinadinovski, Duty Seismologist with Geoscience Australia.

This earthquake occurred at the boundary of two tectonic plates, creating a large fault or offset on the ocean floor. The displacement of the ocean floor generated a sea wave or tsunami, which spread from the epicentre across the Indian Ocean. Tsunami waves are quite small in the deep ocean, but amplify by a factor of 10 or more as the ocean shallows at the coast.

"An earthquake of this size is capable of enormous damage up to several thousand kilometres from its source," said Dr John Schneider, Risk Research Group Leader with Geoscience Australia.

The following animation illustrates how the large tsunami caused by the Great 1833 Sumatra earthquake spreads throughout the Indian Ocean basin. This earthquake was very similar in size and location to the one which occurred on Sunday, 26 December 2004. While the tsunami struck the coast of Sumatra within minutes, it takes several hours to travel the breadth of the Indian Ocean.

These figures from a recent AusGeo News article also illustrate the effect that the tsunami caused by the Great 1833 Sumatra Earthquake had on the entire Indian Ocean basin. Figure (a) shows the tsunami after 2 hours, and figure (b) after 5 hours. The last figure (c) shows maximum wave height attained by the tsunami. While the maximum wave height in the open ocean is only 1.5 metres, when the tsunami reaches shore it 'runs up' to much greater heights, which is why it can be so dangerous. Most of the energy is directed towards the open ocean, and had a strong impact on e.g., the Maldives, much as did the earthquake on 26 December 2004. The recent earthquake was similar in size but occurred further to the north along the Sumatran subduction zone, so it unfortunately had a much greater effect on Sri Lanka and the Bay of Bengal than might have been the case for the 1833 earthquake.

A new standard in geological data

The National Geological Data Model (NGDM v1.0) is a proposed national model for describing features commonly found on digital geological maps. It is the first step towards a fully integrated national, and eventually international, digital geological data standard simplifying compilation, transfer and accessibility across Australia.

Snapshot from the National
Geological Data Model
© Geoscience Australia

The model is designed using a simple data format that can be used as a basis for data transfer between government, industry and academic organisations.

The NGDM v1.0 may be used in a GIS/database environment, but is independent of any particular software associated with those applications. It provides a fully documented logical framework that geologists can use as a starting point for creating their GIS data environment to compile, store and transfer geological map data.

Any comments or suggestions about the data model may be directed to general enquiries. Comments on the data model will be reviewed by the Geological Surveys under the Government Geoscience Information Policy Advisory Committee (GGIPAC).

Geoscience Australia will close down for the holiday period on Friday 24 December 2004, and reopen on Wednesday 5 January 2005.

During this period all general access areas will be closed to the public which includes the Library, The Sales Centre and the Foyer.

Geoscience Australia would like to wish everyone a safe and happy festive season.

Cover of Australia's
Identified Mineral
Resources 2004
© Geoscience Australia

Australia's mineral and solid fuel resources remain reasonably healthy in the short to medium term, according to the latest assessment released by Geoscience Australia.

Australia's Identified Mineral Resources 2004 shows that the nation's current mineral stocks can meet increasing demands for most commodities. However, increased levels of exploration and new discoveries are essential for the longer term sustainability of the minerals industry in Australia.

Australia's Identified Mineral Resources has been published by Geoscience Australia since 1975. The information in this publication is used to formulate Government policy, and provide industry, the investment sector and the general community with an informed understanding of Australia's known mineral resources and exploration activity.

Download or view Australia's Identified Mineral Resources 2004.

In early 2005, the commodity sections from the report will be accessible via the Australian Mines Atlas.