JpGU-AGU Joint Meeting 2017

Presentation information

[EE] Oral

S (Solid Earth Sciences) » S-CG Complex & General

[S-CG62] [EE] Dynamics in mobile belts

Wed. May 24, 2017 10:45 AM - 12:15 PM Convention Hall B (International Conference Hall 2F)

convener:Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Robert Holdsworth(Durham University), Jeanne Hardebeck(USGS), Hikaru Iwamori(Geochemical Evolution Research Program, Japan Agency for Marine-Earth Science and Technology), Chairperson:Bunichiro Shibazaki(International Institute of Seismology and Earthquake Engineering, Building Research Institute), Chairperson:Satoshi Matsumoto(Institute of Seismology and Volcanology, Faculty of Sciences, Kyushu University)

11:30 AM - 11:45 AM

[SCG62-20] Imaging the distribution of transient viscosity following the 2016 Mw 7.1 Kumamoto earthquake

★Invited papers

*James Daniel Paul Moore1, Hang Yu2, Chi-Hsien Tang3, Wang Teng1, Sylvain Barbot1, Dongju Peng1, Sagar Masuti1, Justin Dauwels2, Ya-Ju Hsu3, Valere Lambert5, Priyamvada Nanjundiah1, Shengji Wei1, Eric Lindsey1, Lujia Feng1, Bunichiro Shibazaki4 (1.Earth Observatory of Singapore, Nanyang Technological University, 2.School of Electrical & Electronic Engineering, Nanyang Technological University, 3.Institute of Earth Sciences Academia Sinica, Taipei, Taiwan, 4.International Institute of Seismology and Earthquake Engineering, Building Research Institute, Japan, 5.California Institute of Technology)

Keywords:Rheology, Kumamoto, Geodesy

Postseismic studies of geodetic data following large earthquakes indicate a wide range of mechanisms contribute to the observed deformation and stress relaxation. Both on-fault afterslip and off-fault viscoelastic relaxation can contribute to the postseismic transient phase of the earthquake cycle. One problem with these (quasi-) dynamic models is that there is a wide range of parameter space to be investigated, with each parameter pair possessing their own tradeoffs. This becomes especially problematic when trying to model both on-fault and off-fault deformation simultaneously. Here, we draw insight from postseismic geodetic observations following the 2016 Mw 7.0 Kumamoto earthquake by utilizing a novel inversion technique.

We present a novel approach to invert for on-fault and off-fault deformation simultaneously using analytical Green’s functions for distributed deformation at depth [Barbot, Moore and Lambert., 2016] and on-fault deformation [Okada 1992, Nikkhoo and Walter 2015]. Using these Green’s functions, we jointly invert InSAR images and GEONET GPS time series following the Kumamoto earthquakes for afterslip and lower-crustal viscoelastic flow.

The calculated strain-rates in the lower crust are directly converted to effective viscosities and we investigate the implications of the effective viscosity structure within an outlier-senstitive Bayesian statistical framework to estimate in-situ parameters, such as temperature. Using our new method, we are able to interrogate the transient deformation in the first few months of the postseismic deformation to obtain these parameters.

The postseismic deformation at Kumamoto brings new insights into the distribution of brittle and ductile crustal processes beneath Japan and can be used to infer lower crustal properties.