Journal of the Royal Society of Western Australia, 87:1-8, 2004 
GPS-geodetic deformation monitoring of the south-west seismic 
zone of Western Australia: review, description of 
methodology and results from epoch-one 
W E Featherstone 1 , N T Penna 1 , M Leonard 2 , D Clark 2 , J Dawson 3 , 
M C Dentith 4 , D Darby 5 & R McCarthy 6 
’Western Australian Centre for Geodesy, Curtin University of Technology, GPO Box U1987, Perth WA 6845 
2 Minerals and Geohazards Division, Geoscience Australia, GPO Box 378, Canberra, ACT 2601 
3 National Mapping Division, Geoscience Australia, GPO Box 378, Canberra, ACT 2601 
4 Department of Geology, The University of Western Australia, Crawley, WA 6009 
institute of Geological and Nuclear Sciences, PO Box 30-368, Lower Hutt, New Zealand 
^Western Australian Department of Land Information, PO Box 2222, Midland, WA 6936 
0 W.Featherstone@curtin.edu.au; 3 Nigel.Penna@curtin.edu.au; 0 Mark.Leonard@ga.gov.au; 
£3 Dan.Clark@ga.gov.au; 3 JohnDawson@ga.gov.au; 3 MDentith@geol.uwa.edu.au; 
3 Desmond.Darby@gns.cri.nz; 3 Bob.McCarthy@dli.wa.gov.au 
(Manuscript received January 2003; accepted December 2003) 
Abstract 
The south-west seismic zone (SWSZ) is a northwest-southeast trending belt of intraplate 
earthquake activity that occurs in the south-western corner of Western Australia, and is one of the 
most seismically active areas in Australia. Since the SWSZ lies as close as -150 km from the -1.4 
million population of the Perth region, it poses a distinct seismic hazard. Earthquake activity 
recorded by Geoscience Australia over the past three decades suggests that the SWSZ could be 
deforming by 0.5-5 mmy' 1 . However, little is currently known about the magnitude and orientation 
of this deformation, and whether there is any associated surface expression. Previous geodetic 
studies of the SWSZ that used both terrestrial and Global Positioning System (GPS) techniques are 
inconclusive, due mainly to the imprecision of the technologies used in relation to the likely small 
amount of any surface deformation. Therefore, a new 48-point GPS-geodetic monitoring network 
has been established across the SWSZ to attempt to detect surface deformation, for which epoch- 
one episodic GPS-geodetic measurements were made in May 2002. This paper briefly reviews 
previous attempts to geodetically measure surface deformation across the SWSZ, summarises the 
scientific rationale for the new project, describes the network design and observations used, reports 
on the results of the May 2002 campaign (epoch-one), and discusses future work, including issues 
pertaining to the likely amount of surface deformation that can be detected. 
Keywords: intraplate deformation, geodesy, GPS, south-west seismic zone 
Introduction 
currently known about the magnitude and orientation of 
any deformation. All that is presently known is that the 
western half of Australia is currently subject to an east- 
west-directed compressional stress regime (Reynolds & 
Hillis 2000; Zobak 1992). The expected association of 
surface expressions of deformation with seismic activity, 
though the two are not necessarily interdependent (e.g. 
Jackson & McKenzie 1988), has led to the use of terrestrial 
geodetic monitoring in parts of the SWSZ (discussed 
later). However, the amount of deformation in the SWSZ, 
as inferred from seismic monitoring conducted over the 
last three decades by Geoscience Australia, GA (formerly 
the Australian Geological Survey Organisation, AGSO), 
may be as small as 0.5 mm per annum, thus presenting a 
significant challenge to geodetic monitoring techniques 
in the SWSZ (e.g. Featherstone 1998). If the surface 
deformation were less than the proposed 0.5 mmy* 1 , then 
this would suggest that the recent seismicity is atypical 
at a geological time scale. 
The Australian continent, which lies entirely within 
the Australian tectonic plate, is subject to reasonably 
significant intraplate seismic activity (Wdowinski 1998). 
In Western Australia, a near-linear belt of such activity 
extends in an approximately northwest-southeast 
direction across the south-western comer of the State (Fig 
1), which Doyle (1971) termed the south-west seismic 
zone (SWSZ). The SWSZ is one of the most seismically 
active areas in Australia (e.g. Everingham & Tilbury 
1972), with the notable 1968 Meckering (magnitude 6.9), 
1970 Calingiri (5.7), 1979 Cadoux (6.0), and more recently 
the 2001 Burakin (5.1) and 2002 Burakin (5.2) 
earthquakes. Since the SWSZ lies as close as -150 km to 
the -1.4 million people living in the Perth region, it poses 
a distinct seismic hazard (e.g. Gaull & Michael-Leiba 
1987). 
Knowledge of contemporary deformation is 
potentially an important component in understanding 
the earthquake activity in the SWSZ. However, little is 
Intraplate seismic activity has only received serious 
scientific attention in recent decades (e.g. Wdowinski 
1998; Gaull & Michael-Leiba 1987; Snay et al. 1994). Due 
to the infrequent nature of intraplate earthquakes and 
© Royal Society of Western Australia 2004 
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