Presenter: Hui Lun Chiang
Date: 2017/02/16
Abstract
Large earthquakes do not only deform the crust in the fault, they also change the gravity field of the area which is affected by the earthquake due to mass redistribution in the upper layers of the Earth. This presentation is composed by two researches which studied coseismic and postseismic gravity field with static gravity record from GOCE satellite and monthly satellite gravimetry data from Gravity Recovery and Climate Experiment (GRACE), respectively. In Broerse et al. [2013], the authors noticed the relative sea level changes and mass redistribution of water would have a significant effect on the gravity field in coseismic phase. Therefore, they conducted normal mode model and sea level model after the 2010 Chile (Maule) and 2011 Tohoku-oki earthquakes to predict a gravitationally self-consistent solution for the coseismic relative sea level, surface deformation and gravity field changes. On the other hand, Tanaka et al. [2014] much more focus on the patterns of gravity changes on temporal domain, and they concluded that the gravity variations of the two M9 class earthquakes are similar based on the data derived from GRACE. They found that the postseismic effect might have two components, i.e., short- and long-term gravity changes. Although the mechanisms of short- and long-term postseismic gravity changes are not as clear as coseismic changes at the moment, they might explain some extent with afterslip and the Maxwell viscoelasticity.
Reference
Broerse T., P. Visser, J. Bouman, M. Fuchs, B. Vermeersen, and M. Schmidt (2013), Modelling and Observing the Mw 8.8 Chile 2010 and Mw 9.0 Japan 2011 Earthquakes Using GOCE, International Association of Geodesy Symposia, Volume 139, pp 303-310; doi:10.1007/978-3- 642-37222- 3_40.
Tanaka,Y., and K. Heki (2014), Long- and short-term postseismic gravity changes of megathrust earthquakes from satellite gravimetry, Geophys. Res. Lett., 41, 5451–5456, doi:10.1002/2014GL060559.