Glenn Spinelli

Effects of fluid circulation in ocean crust on subduction zone temperatures and metamorphism

Subduction zone thermal model applications

• Seismogenic zone temperatures

• Sediment alteration and dewatering

• Slab metamorphism

Hypothesis developed for Cascadia

Using temperatures to estimate potential

earthquake rupture area in subduction zones

Thermal limits on subduction zone seismicity

Hyndman and Wang, 1993Blanpied et al., 1991;1995

creep

quake

“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

Using temperatures to estimate potential earthquake rupture area in subduction zones

Hypothesis tested in Nankai

150 – 350 ˚C limits on seismogenic zone applied to:

Cascadia

Hyndman et al., 1993 Oleskevich et al., 1999

Wang et al., 1995 Harris & Wang, 2002

Currie et al., 2002

Gutscher & Peacock, 2003 Hippchen & Hyndman, 2008Marcaillou et al., 2008

NankaiAlaskaChileCosta RicaMexicoRyukuEcuador / ColumbiaSumatraNew Zealand

Fagereng & Ellis, 2009

Nankai thermal state revisited

Spinelli & Wang, 2008

Baba & Cummins, 2005

Spinelli & Wang, 2008

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

Effects of hydrothermal circulation outside the seismogenic zone

• Alteration of incoming sediment

• Slab alteration

Incoming sediment alteration

Slab alteration

Spinelli & Wang, 2009

Fluid circulation in subducting crust yields margin temperatures consistent with:

1) surface heat flux2) sediment alteration 3) slab metamorphism

Conclusions, part 2

warmed

cooled

Thermally modeled subduction zones

Future work

Examine effects of hydrothermal circulation on temperatures in Cascadia and other subduction zones