Great Earthquake Deformation Computations

The 21st Century has seen the occurrence of 17 great earthquakes (Mw>8), including some of the largest earthquakes ever recorded. Numerical modelling of the earthquakes shows that nearly half of the Earth’s surface has undergone horizontal co-seismic deformation >1 mm, with the 2004 Sumatra-Andaman earthquake dominating the global deformation field. This has important implications for both the realisation of a terrestrial reference frame and in the interpretation of regional tectonic studies based on GPS velocities.

Figure 1. Accumulated co-seismic horizontal deformation field of great earthquakes (Mw > 8) since 2000. Focal mechanisms are from the Global Moment Tensor catalog [Ekstrom et al., 2012]. Far-field site velocity errors (red arrows) induced by not accounting for the co-seismic horizontal deformations of the great earthquakes are shown. From Tregoning et al.[2013].

The accumulated global deformation field shows that two regions, Australia and the north Atlantic/Arctic Ocean, have been largely undeformed by these great earthquakes, with accumu lated deformations generally <0.5 mm.

The purpose of this web site is to permit the calculation of the co-seismic horizontal deformations at any location using the models published by Tregoning et al [2013].


We derived model estimates of static co-seismic deformation using a spherical layered model [Pollitz, 1996]. Surface deformation is calculated assuming the PREM elastic stratification [Dziewonski and Anderson, 1981], with a spherical harmonic expansion from degrees 1 to 1500. Please cite Tregoning et al. [2013] if you use this site for computations.

Enter site coordinates (e.g. -65.2, 254.34 ) to calculate the horizontal deformations at the site caused by each of the 15 great earthquakes.

Site Latitude (decimal) :
Site Longitude (decimal):


Tregoning, P., R. Burgette, S.C. McClusky, S. Lejeune, H. McQueen and C.S. Watson, 2013, A decade of horizontal deformation from great earthquakes, J. Geophys. Res., 118, doi:10.1002/jgrb.50154 pdf

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