Seismic Monitoring

SEISMIC MONITORING IN WESTERN AUSTRALIA

• Introduction

• the Geoscience Australia network

• the University of Western Australia network

• the Regional Seismic Network

• temporary Pilbara deployment

• more on Seismic monitoring

--

INTRODUCTION

Before the days of modern instrumentation, only earthquakes which were felt by humans entered the historical record. Nowdays earthquakes are detected by sensitive seismographs, which are installed by research bodies in places of interest around the globe. These can detect minute ground motions, from earthquakes thousands of kilometres distant. Most governments, and many universities run their own networks of seismographs. Most West Australian seismographs are operated by the federal government body, Geoscience Australia, which operates out of Canberra, ACT, and maintains an Australia-wide network. For a brief history on the development of seismographs, click here.

Most of the world's earthquakes occur along the boundaries of the Earth's tectonic plates. Earthquakes within the plates (intraplate earthquakes) are far less common, but still can be large and devastating. Earthquakes are not uncommon in Australia, although many Australian earthquakes pass unnoticed by the general population (because they are relatively small, or may have occurred in a relatively remote part of the country). The two principal bodies responsible for monitoring earthquakes in Australia are Geoscience Australia in Canberra, ACT, and the Seismology Research Centre in Melbourne, Vic. About 400 earthquakes a year are detected by instruments (seismographs) in a region between Geraldton and Albany, WA, called the Southwest Seismic Zone (SWSZ). This region is possibly the most seismically active part of the Australian continent.

If you feel an earthquake, you are encouraged to report it by filling in this on-line form.

The map below shows the locations of seismographs in Western Australia

Seismographs in the region of Perth

< />

THE GEOSCIENCE AUSTRALIA SEISMOGRAPH NETWORK

The table below shows seismographs operated in Western Australia by Geoscience Australia. As the locations may be moved over time, and subtle changes are made to the station code, the original station codes are given. For a more up-to-date list, contact Geoscience Australia, Canberra ACT. Note that there are other stations in Western Australia operated by other agencies, and these are described elsewhere in this section.

UWA seismograph network

A Sprengnether long - period seismograph is operated in the School of Earth and Geographical Sciences. Images from this recorder are regularly posted to http://cyllene.uwa.edu.au/~vdent/SEISMIC

During its period of operation, quite a number of large events have produced good seismograms, and can be found by following the link to ARCHIVES/EQgallery on the above site.

In addition, a number of seismograms from the BRSA station at Mt. Nebo, near Brisbane ( operated by the University of Queensalnd) are included in the directory.

Some of the events to be found in ARCHIVES/EQgallery ( see file EQ-index.txt in that directory) are tabulated below.

In addition to the long period seismograph at UWA, the university runs PSN (public seismic network) stations at a number of locations, including Broome and York High Schools in Western Australia, and Gundaroo Primary School in New South Wales. There is potential to set up seismographs at other locations at a nominal cost. Interested schools or other parties should indicate this on the site feed-back form found elsewhere on this web site.

The Regional Seismic Net

The "Regional Seismic Network" is the name given to a network of low-cost seismographs being developed by the Australian Centre for Geomechanics, based on the UWA campus in Perth, WA. It started operation in 2006 with the establishment of a number of stations at mine sites in the Kalgoorlie - Kambalda region of Western Australia. It then expanded to include networks in the Agnew - Leinster nickel - mining region of Western Australia, and the Beaconsfield Gold Mine in Tasmania

For more information on this network, click here, or to view recent data, follow this link

Joint UWA/ ANU/GA Pilbara seismic deployment

A temporary network of Reftec seismographs was deployed in the Pilbara region of WA in late 2006. The aim of the project is to help identify neotectonic processes in the region. It is a joint project between the UWA, the Austalian National University and Geoscience Australia. It is also supported financially by Woodside Petroleum and Chevron Oil.

For more inforation on this project, contact Dr. Myra Keep of the University of Western Australia

MORE ON SEISMIC RECORDING

Most often, seismographs have a single sensor, sensing vibrations in the vertical plane. These are called one - component stations. The better equipped stations have three components, mounted in the vertical plane, and also NS and EW. All seismic stations these days have an accurate clock with which the incoming signals are timed. Today, these clocks are normally GPS controlled. Geoscience Australia stations today have a telecommunication link, which sends the data directly to GA in Canberra ACT.

Waveforms for user-selectable periods are available on-line, by visiting a website operated by GA www.ga.gov.au/urban/waveform.jsp

Below - GA technician Owen McConnel, who maintains the GA seismic network in Western Australia, from a base in Weshpool, Perth.