1. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Detection of present-day slab-driven mantle flow Michael S. Thorne Edward J. Garnero Allen K. McNamara Heiner Igel Dept. of Geology & Geophysics, University of Utah School of Earth and Space Exploration, Arizona State University Dept. of Earth & Environmental Sciences, Ludwig Maximilians University

2. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Past Ultra-low velocity zone detections McNamara et al. 2010

3. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne SPdKS seismic probe

4. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne 51 high quality events 4221 records SPdKS data set

5. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne 51 high quality events 4221 records SPdKS data set

6. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne PSVaxi Simulations

7. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne PSVaxi Model Space δV S, δV P : (-15%,-5%) (-30%,-10%) (-45%,-15%) (-5%,-5%) (-10%,-10%) (-15%,-15%) δρ: 0%, +10% h: 5, 7.5, 10, 12.5, 15, 20, 30 km width: 1.5°, 3.0°, 4.5°, 6.0°, 12.0° edge: 8.5° - 19.0° in 1.5° increments total: 580 models

8. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Type A&B waveforms & ULVZ position NORMAL ULVZ Model: δV S = -45% δV P = -15% δρ = +10% h = 12.5 km width = 3.0°

9. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Type A&B waveforms & ULVZ position Type A ULVZ Model: δV S = -45% δV P = -15% δρ = +10% h = 12.5 km width = 3.0°

10. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Type A&B waveforms & ULVZ position ULVZ Model: δV S = -45% δV P = -15% δρ = +10% h = 12.5 km width = 3.0° Type B

11. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Type A&B waveforms & ULVZ position ULVZ Model: δV S = -45% δV P = -15% δρ = +10% h = 12.5 km width = 3.0° Type B

12. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Waveform Behavior

13. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Results: Normal, Type A & B locations Tomo: Grand, 2002

14. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne δV S = -45%, δV P = -15% δρ = 10% thickness =10-15 km width ≈ 200-300 km length ≈ 800 km Results: Mega-sized ULVZ

15. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Tomo: Grand, 2002 Mega-sized ULVZ location

16. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Tomo: Grand, 2002 Cross-Section

17. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Thermochemical convection modeling 3 distinct compositional reservoirs i.background mantle ii.LLSVP iii.ULVZ ULVZs preferentially align along LLSVP boundaries ULVZs fast moving, merging ULVZs realign with LLSVP boundaries on hundred million year time scales. McNamara et al. 2010

18. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Development of mega-sized ULVZ

19. michael.thorne@utah.edumichael.thorne@utah.edu http://web.utah.edu/thorne Conclusions SPdKS capable of high resolution mapping of ULVZ position and properties. IF LLSVP’s are thermochemical piles… a)mega-sized ULVZ in LLSVP hole may be indicative of multiple merging piles. b)may give rise to mantle plumes rising near interior edges of piles. c)indeed, mega-sized ULVZ lies directly beneath the Samoa hot spot.