1. Shaking intensity is defined as the severity of ground motion, i.e. displacement, during an earthquake and is assessed using the Modified Mercalli Intensity Scale (MMI). This scale is a good indicator of the effects that an earthquake has on the environment and its population. It is based on three characteristics: People's perception Building performance Changes in the natural environment. MMI is often associated with Peak Ground Acceleration (PGA), which is used to quantify the severity of ground shaking, as shown in Table 1. The intensity of an earthquake is a qualitative measure of the shaking of a location and usually depends by: Magnitude of an earthquake Distance to the fault Local geologyAll of these will affect the way seismic waves propagate through the ground and therefore will be responsible for all subsequent events that occur following the earthquake. Subsidence is the result of earthquake shaking. When the ground shakes, unconsolidated sediments lose their load-bearing strength and the ground “shifts” downward from sea level, causing liquefaction, landslides and flooding. Subsidence can also occur as a result of downward movement on one side of a fault which can sometimes affect large areas of land. The Darfield event on 4 September 2010 generated a magnitude 7.1 earthquake with an MMI of 9. This earthquake resulted in extensive liquefaction and differential subsidence that was located near major streams and rivers around Christchurch. The Christchurch city event on 22 February 2011 created a magnitude 6.3 earthquake with an MMI of 9. This earthquake occurred within 10 kilometers of the city at a depth of 5 kilometres. This cau...... middle of paper ......change and liquefaction in the Avon-Heathcote Estuary. Report no. U11/13, Christchruch: Environment Canterbury Regional Council, 2011.Quigley, M. Van Dissen, R., Villamor, P., Litchfield, N., Barrell, D., Furlong, K., Stahl, T., Duffy, B., Bilderback, E,. Noble, D., Townsend, D., Begg, J., Jongens, R., Ries, W., Claridge, J., Klahn, A., Mackenzie, H., Smith, A., Hornblow, S., Nicol, R. "Surface rupture of the Greendale fault during the Mw 7.1 Darfield (Canterbury) earthquake, New Zealand: initial results." Bulletin of the New Zealand Society for Earthquake Engineering 43:4 (2010): 236-242.SC Cox, HK Rutter, A Sims, M Manga, JJ Weir, T Ezzy, PA White, TW Horton and D Scott (2012). “Hydrological effects of the Mw 7.1 Darfield (Canterbury) earthquake, 4 September 2010, New Zealand.” New Zealand Journal of Geology and Geophysics 55:3 (September 2012): 231-247.