# First Results from Sentinel-1A InSAR over Australia: Application to the Perth Basin
## 3 Study Area  
The city of Perth is located on the Swan Coastal Plain in the central portion of the Perth Basin, an elongated Cainozioc/Mesozoic sedimentary formation spanning \(\sim\)1000 km northwards from the southwestern tip of Australia [40]. The eastern margin is adjacent to the Archean Yilgarn Craton  
Figure 1: Map showing the distribution of past peer-reviewed InSAR studies over Australia: longwall mining in New South Wales [32; 33; 34; 35; 36]; seismicity in Western Australia [30; 31]; and regional-scale studies in the Gippsland Basin, Victoria [37] and the Surat Basin, Queensland [38]. Blue and green coloured regions show where, at the time of writing, more than 10 Sentinel-1A scenes have been acquired. The region used in this study and shown in Figure 2 is highlighted by the red box. (granitic rocks in Figure 2) and is bounded by the near-vertical Darling Fault [41; 42]. The Darling Scarp is located 1 km-3 km east of the Darling Fault and rises steeply \(\sim\)200 m above the Basin, dominating the topography of the region. To the west, the Perth Basin extends for \(\sim\)150 km beneath the Indian Ocean towards the continental rise [40]. The sedimentary succession in the Perth region is \(\sim\)12 km thick [40] and houses numerous freshwater aquifers, the shallowest of which is the unconfined (superficial) aquifer extending to depths up to 70 m [43]. The surface geology that constitutes the unconfined aquifer ranges from clay close to the Darling Scarp, through a succession of fixed sand dunes in the central coastal plain, to limestone along the coastal belt [43] (Figure 2). In northern Perth, the unconfined aquifer is underlain by the semi-confined Mirrabooka aquifer with a thickness up to 160 m [43]. Spanning the entire Perth region are two major confined aquifers that consist of laterally discontinuous siltstones, sandstones and shales. The shallower Leederville aquifer has a thickness of 50 m to more than 550 m, and the deeper Yarragadee aquifer has a thickness of more than 2 km [43]. These four aquifers are the most significant and extensively exploited groundwater resources in the Perth Basin. Groundwater provides \(\sim\)45% of the total water requirement in the Perth Region, with a comparable amount derived from the desalination of seawater. Extraction from the Leederville aquifer began in 1974 and has continued at a rate of \(\sim\)1.41 GL/y. Extraction from the Yarragadee  
Figure 2: Simplified surface geological map of the study region adapted from [PERSON] [43] showing the coverage of InSAR data frames used in this study. The extent of the TerraSAR-X scene is shown by the grey box. The Sentinel-1A scene covers the whole region up to the labelled grey line. Labelled wetlands are those described throughout this study. The Darling Fault, shown by the purple line, marks the eastern margin of the Perth Basin. Red/black squares indicate locations within the metropolitan area described in the text: Hillarys, Frematle and Perth central business district (CBD). commenced in 1979 and increased dramatically between the early 1990s and 2005 from 0.25 GL/y-3.72 GL/y, with the addition of new production bores in northern Perth. Since 2005, the rate of extraction from the Yarragadee has decreased by \(\sim\)1 GL/y [1]. In addition to managed extraction from the confined aquifers, significant extraction occurs from the unconfined aquifer, including from more than 70,000 shallow, private bores (personal communication: Western Australian Department of Water). Changes in the rates of groundwater extraction and recharge are reflected in measurements of hydraulic head (i.e., the elevation to which water rises in a well) made by the Western Australian Department of Water at artesian monitoring bores.