1. School of Civil Engineering; University of Birmingham; Edgbaston, B15 2TT Birmingham UK
2. Faculty of Civil and Environmental Engineering; University of Tun Hussein Onn; Parit Raja Batu Pahat Johor 86400 Malaysia
3. British Geological Survey; Kingsley Dunham Centre; Keyworth Nottingham NG12 5GG UK
4. School of Electronic; Electrical and Computer Engineering; University of Birmingham; B15 2TT UK