1 / 33

Taiwan Nepal Himalaya

Taiwan Nepal Himalaya. Mountain Building: From Earthquakes to Geological Deformation. Mountain building and seismicity in the Nepal Himalaya. Participants. Nepali collaborators S. Rajaure S. Sapkota C. Chitrakar. At Caltech. Pierre Bettinelli (Grad) Laurent Bollinger (Postdoc)

matia
Download Presentation

Taiwan Nepal Himalaya

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. TaiwanNepal Himalaya Mountain Building:From Earthquakes to Geological Deformation

  2. Mountain building and seismicity in the Nepal Himalaya Participants Nepali collaborators S. Rajaure S. Sapkota C. Chitrakar At Caltech Pierre Bettinelli (Grad) Laurent Bollinger (Postdoc) Gweltaz Maheo (Postdoc) Frederic Hermann (Postdoc) J.P Avouac K. Farley D. Helmberger J. Galeztka J. Genrich French collaborators M. Flouzat L. Bollinger

  3. How does high erosion rate at front of the High Range relate to tectonic deformation? Is recent kinematics consistent with the structure and metamorphism that has developed over >20Ma Frederic Herman, Gweltaz Maheo Laurent Bollinger Olivier Beyssac

  4. Model 1: Ramp overthrusting and duplex formation allows for locally high uplift rates.Model 2: Syncronous motion on MCT and STD allows extrusion of the HHC driven by focused erosion

  5. A formal inverse approach Model 1

  6. Model 2

  7. The model with ramp overthrusting and growth of a midcrustal duplex works better. In any case the friction coefficient along the MHT needs to be low (<0.1).

  8. Seasonal strain and seismicity in the Nepal Himalaya Pierre Bettinelli, Laurent Bollinger…

  9. Locked Fault Zone, width  110km Creeping Zone 17-18mm/yr Velocities relative to India

  10. Seismicity and Coulomb stress change due to interseismic stress accumulation (Bollinger et al, JGR, 2004) Seismicity coincides with the area where Coulomb stress increases in the interseismic period

  11. (Bollinger et al, GRL, 2007)

  12. Except for the seasonal fluctuations, ther are no other significant harmonic variations the (at the 1% Probability of Exceedance level)No evidence for EQ triggering by earth tides

  13. LHAS GUMB NAGA DAMA SIMR Displacements relative to India (Bettinelli et al, EPSL, in press)

  14. Seismicity is enhanced in the winter when shortening rate across the Himalayan is largest. (Bettinelli et al, EPSL, in press)

  15. (Bollinger et al, GRL, 2007)

  16. (Bettinelli et al, EPSL, in press) Amplitude of seasonal variations of water storage derived from GRACE

  17. Water level in Ganges Basin determinedfrom TOPEX-POSEIDON and GRACE Water Level and GRACE water heigth (X10) GUMBA-SIMRA N-S Shortening (Bettinelli et al, EPSL, in press)

  18. Deformation of an elastic half space submitted to surface loading (Boussinesq)

  19. Strain induced by surface water level variations in the Ganges basin Summer: Extension Winter: Compression

  20. Coulomb stress varies seasonally with a peak to peal amplitude of about 4kPa (Bettinelli et al, EPSL, in press)

  21. Seismicity rate correlates with stress rate (Bettinelli et al, EPSL, in press)

  22. Conclusions • The spatial distribution of background seismicity in the Himalaya is consistent with triggering by interseismic stress build up. • Seasonal variations of strain and seismicity result from modulation of interseismic stress build up by seasonal surface loading. • At long periods (T> several months), seismicity rate is proportional to stress rate. This correlation can be used to gauge interseismic stress rate. • The correlation between seasonal seismicity rate and stress rate variations, and the ansence of correlation between earthtides and seismicity require the duration of earthquake nucleation time must be of the order of weeks to months

  23. Taiwan Project Participants At Caltech Bruce Shyu (Grad) Martine Simoes (Grad) Ya-Ju Hsu (Postdoc) Olivier Beyssac (Visitor) Jing Yang (Grad) Chen Ji (Grad) Taiwanese collaborators Yue-Gau Chen Shui-Beih Yu Ya-Ju Hsu Yu-Chang Chang, Kuo-Fong Ma, Shiann-Jong Lee, How-Wei Chen, Yi-Min Wu Cheng-Horng Lin J.P Avouac K. Farley K. Sieh M. Simons D. Helmberger J. Tromp J. Genrich J. Galeztka

  24. Malaveille A B C Shyu et al, 2005 Malavielle et al, 2000

  25. (Malavielle et al, 2000)

  26. (Simoes and Avouac, JGR, 2006) The collisional orogen propagates southward at 31mm/yr

  27. from foreland sedimentation: 39-45mm/yr The observed kinematics differs from that expected from the critical wedge theory (if frontal accretion only) ? 15mm/yr Interseismic velocities 16mm/yr No significant internal shortening of the range (Martine Simoes PhD)

  28. Beyssac et al, submitted RSCM Thermometry and Thermochronology

  29. The range must be growing primarily as a result of underplating

  30. (see Posters by Martine Simoes and Frederic Hermann)

  31. Thermal Structure

  32. Downdip limit of Locked Fault Zone, Transition to stable sliding? Transition to Ductile Flow? Effect of temperature on the mechanics ofcrustal deformation?What is the mechanics determining the observed Kinematics?

  33. What’s next? Deep structure of the range From kinematics to mechanics - Long term : how do we explain the proposed kinematics? - Short time scale : earthquake nucleation, Postseismic relaxation (C Wang Yu’s poster)

More Related