upper mantle seismic anisotropy around the plate edge beneath northern taiwan

Download Upper Mantle Seismic Anisotropy around the Plate Edge beneath northern Taiwan

Post on 30-Jan-2016

39 views

Category:

Documents

2 download

Embed Size (px)

DESCRIPTION

Upper Mantle Seismic Anisotropy around the Plate Edge beneath northern Taiwan. Wen-Tzong Liang 1 Yih-Zhen Hsu 2 Bor-Shouh Huang 1 Char-Shine Liu 3. Institute of Earth Sciences, Academia Sinica, Taiwan Institute of Geophysics, National Central University, Taiwan - PowerPoint PPT Presentation

TRANSCRIPT

  • Upper Mantle Seismic Anisotropy around the Plate Edge beneath northern TaiwanWen-Tzong Liang1 Yih-Zhen Hsu2 Bor-Shouh Huang1 Char-Shine Liu3Institute of Earth Sciences, Academia Sinica, TaiwanInstitute of Geophysics, National Central University, TaiwanInstitute of Oceanography, National Taiwan University, Taiwan

  • OutlineTaiwan TectonicsUpper Mantle Anisotropy in the Taiwan RegionNew MeasurementsImplicationsConclusions

  • Taiwan Tectonic SettingManila TrenchSouth China SeaCWB ML 3.5Kuo, 2003IES DMC80 mm/yrWEP

  • Tectonic Evolution of the Northern Taiwan Mountain BeltSouthwest-propagating arc-continent collisionWestward extended Ryukyu subduction and caused flipping of subduction in the northern part of the collision orogenLithospheric stretching induced by the trench suctionCollision orogen collapsed as a result of crustal thinningTeng, 1996NWSE

  • Upper Mantle Anisotropy in the Taiwan Region (I)Splitting in regional and teleseismic shear waves (ScS, S) ignoring source side anisotropyMountain-parallel anisotropyTaiwan Orogen

    Rau et al., 2000

  • Upper Mantle Anisotropy in the Taiwan Region (II)T32A-01 10:20 MCS 302 Seismic anisotropy beneath an active collision orogen of Taiwan from dense array observations Huang et al. GRL (2006)

  • Upper Mantle Anisotropy in the vicinity of Northern Taiwan (SKS)WFSBANPBSKS phases radiated from the 2006/02/22 Mozambique Earthquake (Mw=7.0) occurred ~97 away from N. TaiwanSeismic Stations of BATS/ MT/ YM/ HC/ F-Net NetworksMountain-parallel (on land) vs. Trench-parallel fast direction (in agreement with Long et al. 2005, 2006) t = 0.2 ~ 1.5 s

    Okinawa TroughYNGIGK

  • Upper Mantle Anisotropy beneath Northern Taiwan (SKS)One Backbone NetworkBroadband Array in Taiwan for Seismology (BATS)

    3 Portable BB NetowroksMetropolitan Taipei BB Network (MT)Yangmingshan National Park Network (YM)Hsinchu (HC) BB Network

    Contours of Wadati-Benioff zone are adopted from Chou et al. (2006)100 km150 kmTatun Volcanic AreaCentral RangeTaipeiHsinchu

  • Mantle Wedge Anisotropy beneath Northern Taiwan (local S)Trench-parallel anisotropy in the mantle wedge derived from local deep events

  • Mantle Wedge Anisotropy beneath Northern Taiwan (tele. S)Waveforms generated from deep earthquakes in the Tonga-Kermedec region = 74Incidence angle= 20T0 = 12-15 s210 km410 kmSKStele. SSTrench direction

  • Possible Origins of Upper Mantle Anisotropy in the Northern Taiwan Edge mantle flow?Melt preferred orientationCollision induced mantle deformation beyond the mantle wedgeB-type olivine fabric vs. corner flow

  • Seismic Anisotropy around the Slab Edges in the Western PacificSimilar anisotropy pattern observed in the Kamchatka region (Peyton, et al., 2001; Levin et al., 2004)Trench-parallel in the mantle wedgeTrench-normal beyond the slab edgeSuggesting mantle flow at the slab edge driven by the slab retreat

    Slab edge subjected to an oblique subduction in the Taiwan region

    Pacific PlatePhilippine Sea PlateEurasian PlateTaiwanKamchatka??76 mm/yr80 mm/yr

  • Possible Origins of Upper Mantle Anisotropy in the Northern Taiwan Edge mantle flowMelt preferred orientation?Collision induced mantle deformation beyond the mantle wedgeB-type olivine fabric vs. corner flow

  • 3D Vp and Vs Structural ModelsKim et al., 2005NSOffshoreMantle wedge*Note the color scale is not the conventional one100100 A low velocity layer attached on the slab surfaceACWB dataset

  • Subduction beneath North TaiwanNSNSSNChou et al., 2006bVp %Vp/Vs %Vs %checkerboard testAAAACWB+JMA datasets

  • Possible Origins of Upper Mantle Anisotropy in the Northern Taiwan Edge mantle flowMelt preferred orientationCollision induced mantle deformation beyond the mantle wedgeB-type olivine fabric

  • Slab Collision and FoldingChou et al., 2006aNSNSLateral compression along slab at 50~100 km depth rangeSlab folding

  • Possible Origins of Upper Mantle Anisotropy in the Northern Taiwan Edge mantle flowMelt preferred orientationCollision induced mantle deformation beyond the mantle wedgeB-type olivine fabric

  • B-type Olivine FabricKneller et al., 2005Nakajima & Hasegawa, 2004Jung and Karato, 2001 Katayama et al., 2004

  • 3D Geodynamic Structure in the Taiwan RegionEurosian PlatePhilippine Sea PlateNSLin et al., 2004 Kim et al., 2005 Chou et al., 2006 Wang et al., 2006

  • ConclusionsMountain-parallel anisotropy beyond the mantle wedge implies mantle deformation due to the collision tectonicsTrench-parallel anisotropy exists in the mantle wedge beneath Northern TaiwanSignificant spatial variation of anisotropy beneath ANPB indicates different origins of anisotropy weak coupling between mantle wedge and continental lithosphere?Preserved upper mantle deformation /B-type olivine fabric/ Edge mantle flow/ melt preferred orientationDeployment of Broadband OBS is necessary to study the subduction process in the Taiwan region ongoing!

  • IES Broadband OBS ExperimentThe 1st deployment of BB OBS experiment in the eastern offshore regionKuo and Chi, Sep. 2006http://obs.earth.sinica.edu.tw

  • - Thank you -Syueshan, Taiwan

  • Flow Fields for the Obliquely Subducted Slab3D perspective plots of the particle paths of different scenarios : (a) rotating Euler vectors onto the slab surface

    (b) Flow field minimizing the integrated in-plane deformation rate of the subducted slab

    (c) Flow field minimizing the overall in-plane deformation rate in the entire modeling regionChiao, et al., 2001

  • Melting Features along the Western Ryukyu Slab EdgeLin et al., 2004N

  • Measurement Examples

  • Crustal Deformation in the Central and Southern Ryukyu ArcTrench-parallel extensional strainSouthward migration of Ryukyu ArcBending/retreat of Philippine Sea slab

    Interaction between the Taiwan-Luzon Arc Collision and the bending of Ryukyu Arc.Nakamura, 2004

  • Subduction beneath South TaiwanWang et al., 2006Local/Regional/Teleseismic events joint inversionPrescribed slab

  • Wang et al., 2004

  • Seismic anisotropy and mantle creep in young orogensMeissner et al., 2002Fast LPO of olivine in the direction of mantle creep that is responsible for the Lithospheric Collision

  • Effect of Water and Stress on LPO of OlivineJung and Karato, 2001 Katayama et al., 2004 Jung et al., 2006

Recommended

View more >