GeoFEM Kinematic Earthquake Cycle Modeling in the Japanese Islands

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GeoFEM Kinematic Earthquake Cycle Modeling in
the Japanese Islands 
Hirahara, K.(1), H. Suito(1), M. Hyodo(1) M.
Iizuka(2) and H. Okuda(3) (1)Nagoya
University (2)Research Organization for
Information Science and Technology (3)University
of Tokyo
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Outline
Present status of developing GeoFEM earthquake
cycle simulation module in a local model ( as
Drs. Okuda, Nakajima, Kato and Furumura
presented in this meeting) Simulation of
crustal deformation using kinematic earthquake
cycle based on dislocation model
Northeast Japan model 100 years
Compare present GPS and 100-year conventional
geodetic observations with computed ones
Possible slow slip event in early
1900s ? Southwest Japan model 300
years GPS observed concentrated deformed
zone (NKTZ)
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Earthquake Generation and Strong Motion
in 3-D
Heterogeneous Media
Quasi-Static Modeling of Earthquake Cycle
Interaction on and between Faults
Fault Constitutive Law
Wave Propagation in Heterogeneous Media
Dynamic Modeling of Earthquake Rupture
Simulation and Prediction of Strong Motion
Interplate Earthquake Fault
Inland Active Fault
Frictional Law
Plate Subduction
Viscoelastic Interaction
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Present status of GeoFEM development
Kinematic modeling

• 3-D viscoelastic parallel FEM(time domain)
• Elastic/Maxwell/Standard linear solid
• Dislocation model

In progress

• Contact analysis on plate boundaries, active
• faults
• Implementation of friction law(R/S F)
• Plate motion?Quasi-static slip evolution
• ?Dynamic fault rupture?Strong motion

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Kinematic Earthquake Cycle
using dislocation (Savage,1983)
(a) Interseismic
Steady Motion
Continental plate
Subduction
Oceanic plate
Continental plate?

all decoupled

Oceanic plate
locked

Back Slip
Continental plate
(b) Coseismic

Oceanic plate
locked
Interplate Earthquake
Continental plate

Oceanic plate
locked
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Present stage of our study
?Crustal motion modeling
Based on dislocation model, Simulate the past and
the present crustal motion in Northeast and
Southwest Japan, respectively.
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Interplate Earthquakes in Northeast Japan in the
last 100 years
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GeoFEM Mesh Configuration (Horizontal View)
No.of Nodes 26880 No.of Elements24242
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GeoFEM Mesh Configuration (Vertical View)
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Sources of Crustal Deformation
Assumption of Plate Coupling 100 coupling
Coupling Depth
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Horizontal Displacement since 1900
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Comparison of Recent Horizontal Velocity Field
?GPS Observation? ?Computed Result?
1996-1999
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Comparison of Principal Strain Rate in 100 years
Observation by GSI IshikawaHashimoto(1999)
Computed result
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Possible Slow Slip
Historical Events Assumed 1930 Slow or the
1896 Afterslip Event
Principal Strain Rate in 100 years
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Moment Accumulation
?Fault Planes? ?Moment Accumulation?
Backslip Accumulated Mo 3.31022 (Nm)
Seismic Released Mo 1.371022 (Nm) Aseismic
Released Mo 4.91021 (Nm)
Seismic Coupling 42 57 (including aseismic
slips)
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Southwest Japan
GPS observed velocity
NKTZ
wrt Stable EU 1996-1999
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Southwest Japan
?Assumed tectonic source
1. Subduction of the Philippine Sea plate
Coupling zone 6-30km Backslip rate
2-4-6cm/yr 2. Eastward motion of the Amurian
plate Horizontal velocity 1cm/yr 3.
Subduction of the Pacific plate Coupling
zone 15-60km Backslip rate 8cm/yr
Nodes 24255 Elements21600
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Historical earthquake sequences
Considered earthquakes in this study
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PHSAssumed Coupling distribution
3cm/yr
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10 years after EQ.
Effect of Subducting PHS
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Effect of Subducting PHS
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Present Velocity Field due to PHSand Interplate
Great Earthquakes

Gap
Visco-elastic Effect dominates
Looks like elastic response
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Subduction of PA and Eastward motion of AMR
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Computed Present Velocity Field
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Comparison with observed data