1. Evidence from the A.D. 2000 Izu islands earthquake swarm that stressing rate governs seismicity By Toda, S., Stein, R.S. and Sagiya, T. In Nature(2002), Vol. 419, pg.58-61

2. (K. Yamaoka et al., 2005) Location and Seismicity by S. Nakada Tokyo

3. (K. Yamaoka et al., 2005) Background Seismicity Seismicity record Swarm events during A.D. 2000 ~7000 M ≧ 3 shocks 5 M ≧ 6 shocks Total seismic energy release ~1.5 × 10 4 J 0 -2cm -4cm

4. Swarm evolution (26 Jun ~ 29 July) Off-dyke appears.Expands substantially after two weeks

5. http://sicarius.wr.usgs.gov/animations.html Dike model 8 km 13 km

6. http://sicarius.wr.usgs.gov/animations.html Dike model 8 km 13 km ~20m dike expansions 1.5 km 3 vol. increases

7. Dike-model test Shear stressing rate Seismicity rate change (shear stress rate) ~ 150 bar/yr

8. Dike-model test Dike-model can explain the swarm seismicity. But how about other hypothesis? Heated ground water effect? Propagation rate is not fast enough Heat diffusion? The aftershocks duration is temperature-independent.

9. GPS observation and number of M ≧ 3 earthquakes

10. Main shock and after shocks duration

11. Aftershocks duration time Shear stress rate For the normal stress & duration time: For the M ≈ 6 earthquake close to dike, ~ 0.3d, Calculated stress rate ~150 bar/yr For the background M ≈ 6 shock, ~ 1 yr, Background stress rate ~0.1 bar/yr Aσ~ 0.1 bar (Constant)

12. Methods State variable for seismicity formulation Background seismicity rate Reference stressing rate Seismicity Rate For the daily seismicity rate (without sudden stress drop ) Proportion of normal stress State variable before each time step Shear stress rate

13. Seismicity rate change when shear stress increases

14. Methods For the sudden stress change: Earthquake stress change Proportion of normal stress State variable before each time step State variable for seismicity formulation And also

15. Seismicity rate change when sudden stress drop

16. GPS observation and number of M ≧ 3 earthquakes With GPS and seismicity data, this event would be a good case to test the “Dieterich Law”

17. Aftershocks decay (Observed)(Predicted) ( Aσ~ 0.1 bar ~ constant)

19. If stressing rate model works in a swarm, the rate of damage earthquake can be forecast… (times)

20. Conclusion Rate/state stress transfer furnishes a comprehensive explanation for distributed swarm seismicity, triggering and clustering. It also offers the prospect that near-real-time analysis of seismic and GPS data to forecast during future swarms. The sudden stress change succeeded by a transient stressing rate change can be simulated by combining the two processes.

22. Due to the oscillation of the stressing rate?