William L Ellsworth, Stanford University, Department of Geophysics, Stanford, CA, United States, Kwang-Hee Kim, Busan National Unviversity, Busan, South Korea, Jeong-Ung Woo, Seoul National University, School of Earth and Environmental Sciences, Seoul, South Korea, Francesco Grigoli, University of Potsdam, Potsdam, Germany, Domenico Giardini, ETH Zurich, Zurich, Switzerland and John Townend, Victoria University Wellington, Wellington, New Zealand