The 11 March 2011 Tohoku-Oki (Japan) Megathrust Event: FEM models of Coseismic and Postseismic deformation captured by DInSAR and GPS Data.

Christodoulos Kyriakopoulos1, Salvatore Stramondo1, Marco Chini1, Christian Bignami1, Timothy Masterlark2, Sven Borgstrom4, Francesco Guglielmino3, Giuseppe Puglisi3, Valeria Siniscalchi4

1. Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy. 2. Department of Geological Sciences, University of Alabama, Tuscaloosa, AL, United States 3. Istituto Nazionale di Geofisica e Vulcanologia, Catania, Italy 4. Istituto Nazionale di Geofisica e Vulcanologia, Napoli, Italy.

U51B-0040

PRELIMINARY RESULTSINTRO FINITE ELEMENT MODELThe Mw 9.0 Tohoku-Oki earthquake on March 11 2011 occurred near the northeast coast of Honshu, Japan. No historical records exist of an equal or greater magnitude earthquake along the Japan Trench. The Jogan earthquake of AD 869 may be the only possible exception. The Tohoku-Oki earthquake resulted from a thrust faulting on the subduction zone boundary between the Pacific and North America plates. Previous modeling of the megathrust earthquake indicate that the fault ruptured over an area approximately 400km long (strike direction) by 150 km wide (down-dip direction). In order to investigate the surface displacement field we have applied Differential SAR Interferometry (DInSAR) to Envisat and ALOS PALSAR data. We have processed three strips composed of 13 (track 347, descending orbit), 8 (track 074) and 6 (track 189) Envisat frames over Honshu island. We have also processed ALOS data along ascending path. The interferometric strips cover the whole Honshu Island and the epicentral region and a large coastal area. The strips have been unwrapped to measure the Line Of Sight surface movement. The maximum displacement reaches about 2.5 m relative to a reference point within the entire frames located nearby the southern boundary. They provided a map overview of the interferogram, as well as detailed views of Fukushima, Chiba and Sendai. The Preliminary GPS time series are provided by the ARIA team at JPL and Caltech. All original GEONET RINEX data provided to Caltech by the Geospatial Information Authority (GSI) of Japan. Here we present 3D Finite Element Model (FEMs) for the 11 March earthquake constrained from the available DInSAR and GPS data. The model presented is designed to simulate coseismic and postseismic deformation for the megathrust fault, while simultaneously accounting for the known geologic structure and geophysical context of Japanese subduction zone. We estimate the slip distribution pattern by combining space deformation data and FEMs generated kernels into a linear inversion scheme. Furthermore the coseismic estimated slip is used in a forward problem to predict the viscoelastic deformation. In this poster we present a preliminary slip distribution based on the linear inversion of ONLY the GPS data (ARIA solution + 5 seafloor GPS).

Map of central and northern Honshu, Japan. The yellow star indicates the epicenter of the Mw9.0 11 March 2011 main event. The aftershocks (black dots) are extracted from the USGS catalog and span from March 11 to May 5. Surface displacements due to the Tohoku-Oki earthquake were observed by more than 1200 continuously recording Global Positioning System (GPS) sites (red triangles) installed and operated by the Geodetic Survey of Japan (GSI). The displacement above the hypocenter is detected from 5 GPS installed in the seafloor and using the GPS/acoustic combined technique (Sato et., al 2011).

1. Simulation of the transient Poroelastic deformation2. DInSAR data integration for the linear inversion3. Viscoelastic deformation 4. Afterslip5. Gravity constraints (GOCE ESA mission)

Special Thanks to Dr.Dapeng Zhao and Dr.Zhouchuan Huang for provide us with the seismic tomography of the Honsu Arc.

Oceanic crust elasticE=56GPa ,v=0.31Lithospheric mantleE=150GPa,v=0.25MantleE=150GPa, v=0.25Sed. layer over crust56GPa,v=0.31Volcanic ArcE=40GPa,v=0.34Backarc sedimentE=15GPa,v=0.34Backarc basement70GPa,v=0.28ForearcE=15GPa,v=0.34WedgeE=15GPa,v=0.34

Sed. Over crust

Backarc

Sediment

Volcanic

Arc

Lithosphere

Mantle

Forearc

1300 km

600

km

1300 km

The mesh of the entire model is composed by 1.2 million tetrahedral elements and is generated by CUBIT 12.2 (SANDIA)

Several geophysical features of the Japan trench are implemented into the FE model. Bathymetry and topography from the ETOPO Global Relief Project (NOAA) are implemented as well

The MOHO depression (Huang et al., 2011) caused by the load of the volcanic island is implemented into the FE model

The material properties and geological complexity are taken into account

The whole FE model domain extends L2600 km x W2800 km x H600km. In this poster only the central part of the model is presented

The Subducting slab geometry is implemented from USGS and Gavin Hayes Slab 1.0 project.

In this section we present the Coseismic Slip distribution derived from the linear inversion of 708 GPS points provided by the the ARIA team at JPL and Caltech. In order to constraint better the offshore displacement, geodetic seafloor observations-5 GPS points above the hypocenter-from Sato et al., 2011 are included in the inversion. In the first experiment (W0 inversion) the data are weighted only by the corresponding sigma value while in the second experiment (W10 inversion) the 5 seafloor GPS are weighted by a factor of 10.

Coseismic and postseismic vertical deformation

Coseismic Coseismic + viscoelastic relaxation 20 years

MOHO

W10W0

The viscosity value for the mantle used in this experiment is 1019 Pa*s

• 4.0

• 3.4

• 2.8

• 2.2

• 1.6

• 1.0

• 0.4

• -0.2

• -0.8

• -1.4

• -2.0

• -2.6

• -3.2

(m)

10

15

20

25

5

0

(m)

10

15

20

25

5

0

(m)

Observed vs Modeled vertical GPS dataObserved vs Modeled vertical GPS data

Coseismic slip distributionCoseismic slip distribution

Observed vs Modeled horizontal GPS dataObserved vs Modeled horizontal GPS data

W10W0

W10W0

WORK IN PROGRESS

Coseismic deformation Coseismic + viscoelastic relaxation 10 years

The input coseismic slip distribution is derived from the preliminary inversion presented in the right panel