1. ETS - Science and Hazard the argument for close monitoring November 2008 John Vidale with input from Gomberg, Peng, Creager, Malone, Pratt, Houston, …

2. 2 Topics This is new ground What is ETS and triggered tremor? What is the geometry of locked zones and ETS? How much does tremor and slip encourage large earthquakes?

3. Episodic Tremor and Slip schematic

4. Ide et al., Nature, 2007 Spatial relation of quakes and ETS events in Japan

5. Two kinds of quakes: Fast and slow Ide et al., Nature

6. 6 Creager, yesterday Cascadia ETS: Every 14 months

7. 7 Four tremor zones span Cascadia

8. 8 Episodic tremor and slow slip PGC group

9. 9 UW dense array pilot study 84 sensors in a km 2, Spectrograph of 3 days of heavy tremor directly underneath Time (days)

10. Current affairs What is tremor?What is tremor? –We’re still looking for why tremor and slow quakes have a different scaling than regular earthquakes –Fluid diffusion? –Viscous response? –Simply different rheology of dry rocks?

11. 11 Stress drives tremor but does tremor ignite megathrust? Rubinstein et al.

12. 12 Not so different on San Andreas Fault - tremor excited by big teleseisms Peng et al.

13. Widespread tremor from 2002 Denali Gomberg, Rubinstein, Peng, Creager, Vidale, Bodin Science, 2008

14. 14 Rubinstein et al.

15. 15 Maybe shaking ignites ETS (but does ETS ignite megathrust?) Rubinstein

16. 16 Shaking as a tremor meter Rubinstein

17. Spatial relation of ETS-locking Creager PGC

18. 18 Future? Alarmist?

19. 19 Ways forward Rapidly moving research 1. Measure ETS correlation with subduction earthquakes globally. 2. Nail down single model –location of ETS slip –locked zone. 3. Find ETS Gutenburg-Richter distribution of magnitudes, determine moment scaling. 4. Ascertain cause of slow ETS scaling. Naval Safety Center

20. 20 The end