1. Glenn Spinelli Effects of fluid circulation in ocean crust on subduction zone temperatures and metamorphism

2. Subduction zone thermal model applications Seismogenic zone temperatures Sediment alteration and dewatering Slab metamorphism

3. Hypothesis developed for Cascadia Using temperatures to estimate potential earthquake rupture area in subduction zones

4. Thermal limits on subduction zone seismicity Hyndman and Wang, 1993 Blanpied et al., 1991;1995 creep quake

5. “A critical confirmation of the constraints on the seismogenic zone provided by thermal models is comparison with actual thrust earthquake data.” Hyndman and Wang, 1993 Extent of Cascadia seismogenic zone estimated from thermal models

6. Using temperatures to estimate potential earthquake rupture area in subduction zones Hypothesis tested in Nankai

7. 150 – 350 ˚C limits on seismogenic zone applied to: Cascadia Hyndman et al., 1993Oleskevich et al., 1999Wang et al., 1995Harris & Wang, 2002Currie et al., 2002 Gutscher & Peacock, 2003Hippchen & Hyndman, 2008Marcaillou et al., 2008 Nankai Alaska Chile Costa Rica Mexico Ryuku Ecuador / Columbia Sumatra New Zealand Fagereng & Ellis, 2009

8. Nankai thermal state revisited Spinelli & Wang, 2008 Baba & Cummins, 2005

9. Spinelli & Wang, 2008

10. Conclusions, part 1 When fluid circulation in subducting crust is considered, Nankai seismogenic zone extends from ~150 - 350 ˚C Including hydrothermal circulation reduces Nankai seismogenic zone temperatures by 20 - 100 ˚C

11. Effects of hydrothermal circulation outside the seismogenic zone Alteration of incoming sediment Slab alteration

12. Incoming sediment alteration

13. Slab alteration Spinelli & Wang, 2009

14. Fluid circulation in subducting crust yields margin temperatures consistent with: 1) surface heat flux 2) sediment alteration 3) slab metamorphism Conclusions, part 2 warmed cooled

15. Thermally modeled subduction zones

16. Future work Examine effects of hydrothermal circulation on temperatures in Cascadia and other subduction zones