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GeoFEM Kinematic Earthquake Cycle Modeling in the Japanese Islands

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. Outline.

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GeoFEM Kinematic Earthquake Cycle Modeling in the Japanese Islands

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  1. 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

  2. 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 1900’s ? ・Southwest Japan model: 300 years GPS observed concentrated deformed zone (NKTZ)

  3. Earthquake Generation and Strong Motion in 3-D Heterogeneous Media Quasi-Static Modeling of Earthquake Cycle Fault Constitutive Law Interaction on and between Faults Wave Propagation in Heterogeneous Media Dynamic Modeling of Earthquake Rupture Simulation and Prediction of Strong Motion Inland Active Fault Interplate Earthquake Fault Frictional Law Plate Subduction Viscoelastic Interaction

  4. 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

  5. Kinematic Earthquake Cycle using dislocation (Savage,1983) (a) Interseismic Steady Motion Continental plate Subduction Oceanic plate Continental plateト ***** all decoupled ＝ Oceanic plate locked ＋ Back Slip Continental plate (b) Coseismic ***** Oceanic plate locked Interplate Earthquake Continental plate ***** Oceanic plate locked

  6. 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.

  7. Interplate Earthquakes in Northeast Japan in the last 100 years ★Slow Slips 　・In 1989，1992 Off Sanriku Strain meters KAWASAKI et al. (1995) 　・the 1994 Off Sanriku Eq. Afterslip （GPS） HEKI et al. (1997) 　・1978 Off-Miyagi Afterslip (Leveling) UEDA et al. (2001) 1994～1995 1989 1992 1978～1979

  8. GeoFEM Mesh Configuration (Horizontal View) A A’ No.of Nodes ：26880 No.of Elements：24242

  9. GeoFEM Mesh Configuration (Vertical View)

  10. Sources of Crustal Deformation １．Subduction of PA 15-60 km ２．Subduction of AM 0-30 km ３．Interplate Earthquakes Since 1890（M>7.4）17 eqs. ４．1896 Riku’u Earthquake Assumption of Plate Coupling *100% coupling * Coupling Depth

  11. Horizontal Displacement since 1900 ★Year Interplate Earthquakes★ 1936Kinkazan 1938Shioya 1940Shyakotan 1952Tokachi 1958Etorof 1964Niigata 1968Tokachi 1969Eastern Hokkaido 1973Nemuro 1978Miyagi 1983Central Japan Sea 1993Southwest Hokkaido 1994Off-Sanriku

  12. Comparison of Recent Horizontal Velocity Field 〇 and × ：　　　　　　　　　　　 〇　　　　　　　　　　　 ・Westward rate of 2cm/yr along the Pacific coast ・Western Hokkaido × ・Northern Hokkaido； Eastward rate ・Northern Tohoku； Small rate ★GPS Observation★　★Computed Result★ 1996-1999

  13. Comparison of Principal Strain Rate in 100 years Observation by GSI [Ishikawa・Hashimoto(1999)] Computed result

  14. Possible Slow Slip Historical Events + Assumed 1930 Slow or the 1896 Afterslip Event Principal Strain Rate in 100 years

  15. Moment Accumulation ★Fault Planes★　★Moment Accumulation★ Backslip Accumulated Mo = 3.3×1022 (Nm) Seismic Released Mo = 1.37×1022 (Nm) Aseismic Released Mo = 4.9×1021 (Nm) Seismic Coupling 42% 57% （including aseismic slips）

  16. Southwest Japan GPS observed velocity NKTZ wrt Stable EU 1996-1999

  17. 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 Elements：21600

  18. Historical earthquakesequences Considered earthquakes in this study

  19. PHS:Assumed Coupling distribution 3cm/yr

  20. 10 years after EQ. Effect of Subducting PHS

  21. Effect of Subducting PHS

  22. Present Velocity Field due to PHSand Interplate Great Earthquakes Gap Visco-elastic Effect dominates Looks like elastic response

  23. Subduction of PA and Eastward motion of AMR

  24. Computed Present Velocity Field

  25. Comparison with observed data

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