World topography
Most earthquakes occur in subduction zones
Trench-Arc-Backarc system Landward side Seaward side Back- Fore-
(Widiyantoro et al., 1999 EPSL)
Seismicity cross section across Japan trench http://www.eps.s.u-tokyo.ac.jp/epenv/members/shimidzu.html
(Gagnon et al., 2005 Nature) measured horizontal surface motion perpendicular to the trench is consistent with a model having no slip along the thrust fault between 2 and 40 km depth.
a Phase transition due to eclogite formation, making the lithosphere heavy. 100 km (4) (3) (2) (1) (4) (3) (2) (1) eclogite 50 km P= ρgz = 3300*9.8*depth ~ 3e4*depth 100km 1e5*3e4=3e9 Pa = 3GPa
Possible Cause for difference in low-velocity zone & arc volcanism PM Eclogite Low V Low V Eclogite PM Eclogite PM Eclogite NE: Blueschist (dehydration) Eclogite110->160 km depth SW: Greenschist.amphibolite Ecolgite: 50-60 km depth (Peacock and Wang, 1999 Science) Another Case in the Middle America Trench Partial melting and dehydration at 60-120 km depth PM (Peacock et al., 2005 PEPI)
1)Trench-outer rise seaward of the trench when the plate is forced to subduct - to carry chemically-bound water into the deep subduction zone 2) As fluids are released from the downgoing plate and infiltrate the mantle wedge. - Seismogenesis as serpentines are weak; thus, they limit the size of the seismogenic megathrust fault and hence earthquake hazards. https://sfb574.geomar.de/subproject-a5.html (Ranero et al., 2003 Nature) Oceanic plate hydration and dehydration model (Faccenda et al., 2012 G3) http://147.162.183.151/personal/faccenda-manuele
Two end-members of subduction zone Uyeda and Nishiwaki, 1980 Mariana Type: Near-vertical subduction Back-arc basin No great earthquakes Chilean Type: Shallow subduction No Back-arc basin Great earthquakes Interplate motion (deformation)-kinematics Interaction (stress) Seismic activity.
Accretion vs. Erosion Thick sediment above subducting plate case: Shallow sediment is accreted to the landward plate. Thin sediment case: Subducting plate erodes the hanging wall block. (Clift and Vannucchi, 2004) (Saffer and Tobin, 2011)
Accretion vs. Erosion The accretionary prism develops if the subducting plate has a thick sediment and is subducting slowly. (Clift and Vannucchi, 2004) Geological record of fluid flow and seismogenesis along an erosive subducting plate boundary (Vannucchi et al., 2008 Nature)
(Saffer and Tobin, 2011) (Kimura et al., 2012) 150 100 (Kimura et al., 2007)
Nankai Trough: World s famous accretionary prism
(ODP Leg146 Initial Results)
(Maltman et al., 1997; SR156) (156 Science Party,1995; IR156) Thin sediment above the subducting plate Hanging-wall materials are eroded. (Von Huene et al., 2004 Geology)
(Nakamura et al., 2014EPS)