1. Sicily - 1990 Top Driven Asymmetric Mantle Convection Don Anderson Carlo Doglioni

2. Modified after Thybo, 2006 LowVelocity Zone Riguzzi et al. 2010 Tectonophysics decoupling Vs, km/s

3. Modified after Thybo, 2006 LowVelocity Zone Riguzzi et al. 2010 Tectonophysics

4. 160018002000 K Canonical 1600 K adiabat SUBADIABATIC REGION Modified after Xu et al. 2011, GJI Depth km Vs 100 300 Dry lherzolite solidus 50 ppm H 2 O Tp 4 km/s Vs wavespeed 4.55.05.5 Geotherm from seismic gradients Thermal bump region (OIB source) SUPERDIABATIC REGION T LVZ CONDUCTIVE LITHOSPHERE insulation Lehmann discontinuity 200 pargasite breakdown

5. Cuffaro & Doglioni, 2007 GSA Sp. Publ. Tectonic Equator WESTWARD DRIFT OF THE LITHOSPHERE AND TECTONIC EQUATOR Shallow hotspot reference frame

6. Cuffaro & Doglioni, 2007 GSA Sp. Publ. Westward drift of plates constrained by viscosity variations in the LVZ LVZ

7. Modified after Yuan & Beghei, 2013 EPSL In Doglioni & Anderson 2015, GSA-AGU Volume The tectonic equator fits the SKS of the LVZ

8. Mid Atlantic Ridge Asymmetric rifts Doglioni et al. 2014, Geoscience Frontiers

9. Panza et al. 2010 Geology Asymmetric S-wave signature of ridges (faster western side)

10. Chalot-Prat & Doglioni in prep. Westerly migrating ridge  LVZ & LID lateral heterogeneity & asymmetry

11. KURILI N-CORDILLERA Harabaglia & Doglioni, 1998, GRL Asymmetric signature of topography and gravity

12. Riguzzi et al. 2010, Tectonophysics Asymmetric dip of slabs moving along the tectonic equator

13. slab dip vs. lithosphere age same dip for variable ages = no correlation Cruciani et al., 2005, EPSL No negative buoyance as cause of

14. Doglioni et al. 2007 ESR

17. CONVERGENCE HINGE WRT UPPER PLATE SUBDUCTION RATE VOLUME RATE lengthmm/yr km3/yr N-AmericaBarbados2273020 4,5 S-AmericaSandwich1582018 S-America- AntarcticaAleutians367465158037,9 Macquarie- NewZealandCarpathians11100220,3 Papua- NewGuineaN-Japan103980-19616,5 Indonesia Nankai- Ryukyu-Phil.432070239339,3 Himalaya Izu Bonin- Marianas470350308037,6 Zagros NNewZealand- Tonga-Kerma32338010018058,2 Dinarides Bismarck- Solomon345760208027,7 HellenidesBanda2555010 2,5 CyprusApennines17003251 Taiwan- BorneoTotal length31787 232 Alps New Hebrides Caucasus Total length CONVERGENCE HINGE WRT UPPER PLATE SUBDUCTION RATE VOLUME RATE lengthmm/yr km3/yr N-America257337-18194,9Barbados S-America990066-353130,7Sandwich S-America- Antarctica16412214121,9Aleutians Macquarie- NewZealand25636-420,5Carpathians Papua- NewGuinea25115-320,5N-Japan Indonesia512775-502512,8 Nankai- Ryukyu-Phil. Himalaya299536-3061,8 Izu Bonin- Marianas Zagros353924-14103,5 NNewZealand- Tonga-Kerma Dinarides11144-310,1 Bismarck- Solomon Hellenides95236-15212Banda Cyprus73110-550,4Apennines Taiwan- Borneo286060-35257,1Total length Alps8501-0,50.50,04 New Hebrides309860-40206,2 Caucasus248112861,5 Total length44728 74 E-NEW-SW Slab recycling volumes ≈ 306 km 3 /yr Doglioni & Anderson, 2015, GSA-AGU Volume 3 times larger volumes of lithosphere are westerly subducted

18. Doglioni et al. 2007 ESR

19. Ritsema, 2003 Faster velocity at 600 km of the western Pacific: cooler and deeper western slabs

20. B NE A 0 km 90 60 30 NW 2 vergences 1 vergence 0 km 90 60 30 Dal Piaz, 1997 Scrocca et al., 2005, Tectonics 1300°C basement Asymmetric subductions & related orogens

21. S=H-L convergence<subductionconvergence>subduction heat flow VS=VH-VL Asymmetric subductions and related orogens Doglioni et al. 2007 ESR

22. Doglioni & Anderson, 2015 GSA-AGU Volume

23. “Westward” drift of the lithosphere Doglioni & Anderson, 2015 GSA-AGU Volume POLARIZED CONVECTION

24. Doglioni & Anderson, 2015 GSA-AGU Volume “Westerly” sheared lithosphere: Slab pull or horizontal tidal torque? confined descentdiffused compensating passive ascent ridge

26. It is the asymmetry that generates the phenomenon PIERRE CURIE Thanks to: Eugenio Carminati, Mattia Crespi, Françoise Chalot-Prat, Marco Cuffaro, Fabrizio Innocenti, Anatoli Levchin, Giuliano Panza & Federica Riguzzi