1 / 19

Geophysical study of the crust and upper mantle in the Qinghai-Tibet Plateau, China:

Geophysical study of the crust and upper mantle in the Qinghai-Tibet Plateau, China: Broadband seismic observations and tomography imaging of the lithosphere in southern and central Tibetan. He Rizheng, Gao Rui, Zheng Hongwei (CAGS, Cnina) Zhao Dapeng (Northeastern University, Japan ).

milos
Télécharger la présentation

Geophysical study of the crust and upper mantle in the Qinghai-Tibet Plateau, China:

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. Geophysical study of the crust and upper mantle in the Qinghai-Tibet Plateau, China: Broadband seismic observations and tomography imaging of the lithosphere in southern and central Tibetan He Rizheng, Gao Rui, Zheng Hongwei (CAGS, Cnina) Zhao Dapeng (Northeastern University, Japan ) USA,2008-11-11

  2. Since Paleozoic, Multiple collisions in diferent geological eras have sequentially produced near E-W tendings structures, such as sutures, thrust and folds, thrust and normal faults.

  3. Since ～17Ma, strong E-W extending took place in the Tibet, as some sequence of collision of India plate with Eurasian plate( Armijo et al,1989; Yin An et al，2000). （Kapp and Guynn，2004）

  4. Typical Models for Tibet uplifting (Argand, 1924) (Zhao and Morgan, 1987) The Key question was deep structure under the central Tibet needed to be known. (Dewey and Burke, 1973) (Hamburger et al., 1992) (England and Houseman, 1989) (Tapponnier et al., 1982) http://www.geo.arizona.edu/~ozacar/models~1.html

  5. To understand those key questions,hundreds of broadband stations deployed in Tibet in past two decades. 05-06 08-09 07-09 04-05 05-06 03-04 03-04

  6. 305 Stations used in this study To understand above-mentioned questions, we collect the datasets of several projects, such as INDEPTH-I,II,III, HIMNT, ISC etc, which had been carried out in the central Tibet. All of stations used sum up to 305 stations. 3-D Tomography method used was from Zhao Dapeng (1992,1994, 2001) .

  7. P-wave images at various depths: From 0 km to 100 km • Low P-velocity under Tethyan Himalaya is shallower than Moho depth. • 2. Velocity structure of Lhasa Terrane was more complicated. • 3. Low-velocity anomaly boday located beneath YGR, which is the most scale rift in the Central Tibet. • 4. As a whole, the strike of velocity anomaly body is similar to suface tectonic trend.

  8. P-wave images at various depths: From 150 km to 400 km • The trending of P-velocity anomalous bodies had varied from E-W in the crust to nearly S-N. • 2. low P-velocity anomalous body beneath Tethyan Himalaya disappered.

  9. Comparing with the existing results （He et al.,2006） (Tilmann et al., 2003)

  10. Comparision between the profile along Tibetan Highway from our group and the result of Owens and Zandt（1997）.The above one is from Owens and Zandt（1997),the below one is from this study. （Zheng et al.,2006)

  11. Tomographic images of E-W profiles along 25°N show that Indian Lithosphere had a bend. （Zheng et al.,2006）

  12. Tomographic images of the Indian Lithosphere can be continuously traced from N24°to N34° under E88° profile. （Zheng et al.,2007）

  13. The frontier of subducted Indian Lithospheric Mantle White solid-lines show the location of the frontier of subducted ILM projected to the surface. Black dash-lines denote the location needing to be confirmed. The dash-line contour shows a low Pn and high Sn attenuation zone (McNamara, 1994 ). （He et al.,2006）

  14. Our Conclusions • 1. The frontier of ILM presently located beneath the central Qiangtang Terrane, about N34°. • ILM deformed, which was similar to that of the SCOOP , with about NE strike.The deformation of ILM resulted of Extending in the region. • 3. The partial melting materials beneath Tethyan Himalaya maybe resulted of lecuogranites in the High Himalaya and Tethyan Himalaya.

  15. The zone of uneffect Sn-Low Pn Is similar to the potassic vocanic zone Vocanism in Northern Tibet is hard to understand Cenozoic Potassic magmatism in the central Tibetan happened during Tibetan uplifting (Hacker et al., 2000; Ding et al., 2003William et al,2004; Chung et al，2004; Guo et al., 2006).

  16. Seismicity Map (Mb>3.0) from USGS Hotan JSS Ando Nyma Zongba Dangxiong From 01,Jan to 08, Nov

  17. 09-10 05-06 08-09 10-11 07-09 04-05 05-06 So, we make a plan that we will deploy hundreds of BB stations with ~10km space along the S-N profile along E88.5 °from JSS to KLS, and E-W profile along N34° or N35°from E83° to E95°to cross the Lavas zone in Northern Tibet to capture some images of deep structure under the zone. 03-04 03-04

  18. Thank you for your attentions! 2008-09-18

  19. Cartoon of ILM under central Tibet (E85° to E90°) (Tilmann et al., 2003) (Yin & Harrison, 2000 ) (He et al.,2006)

More Related