From Subduction to Collision :

Taiwan

from Angelier

Participants

J.P AvouacK. FarleyH. KanamoriT. HeatonD. HelmbergerChen JiK. SiehM. SimonsJ. Tromp

Taiwanese partnersYue-Gau ChenShui-Beih YuYu-Chang Chang,Kuo-Fong Ma, Shiann-Jong Lee, How-Wei Chen,Yi-Min WuC.H. Lin

Bruce Hsu (Grad)Martine Simoes (Grad)Jing Yang (Grad)Ya-Ju Hsu(Postdoc)Yoshi Kaneko (Grad)Olivier Beyssac (Visitor)…

Malaveille

(Malavielle et al, 2000)

Malaveille

(Malavielle et al, 2000)

(Malavielle et al, 2000)

Mapping active faults (Bruce,Kerry), Kinematics of long term deformation,

across the longitudinal valley

From Bruce, Kerry and Yu-Gau

Ground displacements as measured by GPS – Before the Chichi EQ

(black arrows)– Effects of the Chichi EQ

(red arrows)

(Dominguez et al, 2003)(Dominguez et al, 2003)

Why a TO project on Taiwan Tectonics?

• Transition from subduction to collision : Lateral variation may reveal the time evolution of the mountain belt since the “end” of the subduction)

• Archetype of active mountain belt : Revisiting “the critical taper model”; an opportunity to understand better interplay between crustal deformation, evolution of thermal structure and denudation.

• Toward a physical model of the seismic cycle : A unique area where we can put together information about large EQ, crustal strain in the interseismic period, intense background seismicity, structural geology,

• Connection with Taiwanese colleagues

• Task 1 : Determinination of the kinematics of crustal deformation (morphotectonics). This action requires some field work. DEM and sat images analysis. Dating of geomorphic surfaces

• Task 2 : Determination of peak metamorphic temperatures and denudation along transects across Taiwan. This action implies some field work for thermobarometry, thermochronology and structural geology. Model the thermal structure based on these data the the kinematic results from task 1.

• Task 3 : Geodetic measurements and modeling of the current pattern, and test consistency with seismicity distribution and possible rate changes. A support to some data acquisition could be envisioned, for example additional GPS stations.

• Task 4 : Analysis of seismicity data for structural investigations. Analysis of local and regional seismic waveforms from the Taiwan networks to determine the crust and upper-most-mantle structure (slabs, intracrustal thrust faults) and their relationship with seismic events and seismicity. We envision the development of a detailed 3d model showing the transition from subduction to collision. Re-examination of prior events with the globally calibrated paths (using the ChiChi EQ).

• Task 5 : Mechanical modeling. Lithospheric deformation associated with the transition from subduction to collision. Modeling of the seismic cycle with proper account for faults geometry, thermal structure, stress distribution.

Some Geology, Geophysics and modeling

Task 1: Kinematic of deformation along the Longitudinal valley

From Bruce, Kerry and Yu-Gau

Task 1 : Kinematic of deformation along the westerm foothills

from Martine

Task 2 : Testing a model of mountain building : 1- Kinematics

GPS measurements of Pre-seismic displacements modelled by a creeping sub-horizontal elastic dislocation Central range.

(Dominguez et al, 2003)

Task 3: GPS measurements coseismic deformation

~ 100 RSCM temperatures~ 40 (U-Th)/He ages

From Olivier, Ken

Task 2 : Metamorphic petrology and Thermochronology

From Olivier

(Dominguez et al, 2003)

Task 3: GPS measurements of interseismic deformation

Task 3: GPS measurements of postseismic deformation

from Yaru and Shui-beih

Postseismic displacement at station I007Can we reconcile the time evolution of

seismicity and deformation?

Perfettini and Avouac, 2004

So far, see posters

• Task 1 : – Active faults map of Taiwan (Bruce and

coll), – Kinematics of deformation across the

longitudinal valley (Bruce and coll)– Deformation rate across the western foothill

(Martine and coll)• Task 2 :

– Thermometry Thermochronology across the central range (Olivier and coll)

• Task 3 :– Postseismic deformation following Chichi

(Yaru and coll.)• Task 4 :

– Deep structure revealed from afterschock waveforms (Yoshi and coll).