全部 标题 作者
关键词 摘要

OALib Journal期刊
ISSN: 2333-9721
费用:99美元

查看量下载量

相关文章

更多...

藏西北地幔过渡带地震波速度结构研究

, PP. 700-712

Keywords: 地幔过渡带,地震波速度,藏西北

Full-Text   Cite this paper   Add to My Lib

Abstract:

?本文利用三重震相波形模拟获得了藏西北地幔过渡带近东西向剖面的SH波和P波速度结构.震源深度偏移波形叠加的方法可验证数据的一致性,提高三重震相识别的可靠性.研究发现,藏西北过渡带的SH波和P波速度结构并不简单线性相关.过渡带内SH波速度梯度小,其660km间断面速度跳跃大;而P波速度结构则表现为过渡带内速度梯度大,且660km间断面速度跳跃小.与此同时,两种速度结构均显示660km间断面埋深无明显异常.上述结果与藏中和拉萨块体过渡带速度结构基本一致与印度地盾下方相比,研究区过渡带底部SH波速度相当,而P波略显高速,因而Vp/Vs比值稍大.结合矿物物理研究,我们认为地震波速度异常的差异可能主要是由过渡带内化学成分的横向不均匀性,例如铝含量的增多引起的.考虑到青藏高原的构造演化,研究区过渡带内铝含量的增多可能与高原形成过程中特堤斯洋板片的俯冲-拆沉有关.

References

[1]  1 Davies G F, Richards M A. Mantle convection. J Geol, 1992, 100: 151-206??
[2]  2 Ringwood A E. Phase transformation in the mantle. Earth Planet Sci Lett, 1969, 5: 401-412
[3]  3 Ito E, Takahashi E. Postspinel transformations in the system Mg2SiO4-Fe2SiO4 and some geophysical implications. J Geophys Res, 1989, 94: 10637-10646??
[4]  10 Gao W, Matzel E, Grand S P. Upper mantle seismic structure beneath Eastern Mexico determined from P and S waveform inversion and its implications. J Geophys Res 2006, 111: BO8307, doi: 10.1029/2006JB004304
[5]  11 Chen W P, Tseng T L. Small 660 km seismic discontinuity beneath Tibet implies resting ground for detached lithosphere. J Geophys Res, 2007, 112: B05309, doi: 10.1029 /2006JB004607
[6]  12 Tseng T L, Chen W P. Discordant contrast of P- and S-wave speeds across the 660 km discontinuity beneath Tibet: A case for hydrous remnant of sub-continental lithosphere. Earth Planet Sci Lett, 2008, doi: 10.106/j.epsl.2008.01.038
[7]  13 Chu R S. Upper mantle velocity structure beneath the Tibetan Plateau from triplicated seismic P waveforms. Doctor Dissertation. Saint Louis University, 2008
[8]  14 Tilmann F, Ni J. INDEPTH III. Seismic team Seismic imaging of the downwelling Indian lithosphere beneath central Tibet. Science, 2003, 300: 1424-1427 ??
[9]  15 Li C, Hilst R D, Toksoz M. Constraining P-wave velocity variations in the upper mantle beneath southern Asia. Phys Earth Planet Inter, 2006, 154: 180-195??
[10]  16 Huang J L, Zhao D P. High-resolution mantle tomography of China and surrounding regions. J Geophys Res, 2006, 111: B09303, doi: 10.1029/2005JB004066
[11]  17 Kind R, Yuan X H, Saul J, et al. Seismic images of crust and upper mantle beneath Tibet: Evidence for Eurasian Plate subduction. Science, 2002, 298: 1219-1221??
[12]  18 Sol S J, Meltzer A, Zurek B, et al. Insight into the lithospheric structure and deformation in Eastern Tibet from splitting and travel time variations of core phases. Eos Trans Amer Geophy Union, 2004, 85: Abstract T31A-1279
[13]  19 Yao H, van der Hilst R D, De Hoop M V. Surface-wave array tomography in SE Tibet from ambient seismic noise and two-station analysis: I -Phase velocity maps. Geophys J Int, 2006, 166: 732-744, doi: 10.1111/j.1365-246X.2006.03028.x??
[14]  20 Pegler G, Das S. An enhanced image of the Pamir-Hindu Kush seismic zone from relocated earthquake hypocenters. Geophys J Int, 1998, 134: 573-595??
[15]  21 Fuchs K, Muller G. Computation of synthetic seismograms with the reflectivity method and comparison with observations. Geophys J R Astron Soc, 1971, 23: 417-433
[16]  23 Boyd O S, Jones C H, Sheehan A F. Foundering Lithosphere Imaged Beneath the Southern Sierra Nevada, California, USA. Science, 2004, 305: 660-662 ??
[17]  24 Cammarano F, Goes S, Vacher P, et al. Inferring upper mantle temperatures from seismic velocities. Phys Earth Planet Int, 2003, 138: 197-222??
[18]  26 Yusa H, Inoue T, Ohishi Y. Isothermal compressibility of hydrous ringwoodite and its relation to the mantle discontinuities. Geophys Res Lett, 2000, 27: 413-416??
[19]  27 Jacobsen S D, Smyth J R, Spetzler H, et al. Sound velocities and elastic constants of ironbearing hydrous ringwoodite. Phys Earth Planet Int, 2004, 143-144: 47-56
[20]  28 Jacobsen S D. Effect of water on the equation of state of nominally anhydrous minerals. Rev Mineral Geochem, 2006, 62: 321-342??
[21]  29 Wang Y, Wen L X, Weidner D. Upper mantle SH- and P-velocity structures and compositional models beneath southern Africa. Earth Planet Sci Lett, 2008, 267: 596-608??
[22]  30 Estabrook C H, Kind R. The nature of the 660-kilometer upper-mantle seismic discontinuity from precursors to the PP phase. Nature, 1996, 274: 1179-1182
[23]  31 Shearer P M, Flanagan M P. Seismic velocity and density jumps across the 410- and 660-kilometer discontinuities. Science, 1999, 285: 1545-1548??
[24]  32 Higo Y, Inoue T, Irifune T, et al. Effect of water on the spinel-postspinel transformation in Mg2SiO4. Geophys Res Lett, 2001, 28: 3505-3508??
[25]  33 Van der Voo R, Spakman W, Bijwaard H. Tethyan subducted slabs under India. Earth Planet Sci Lett, 1999, 171: 7-20??
[26]  4 Niu F, Kawakatsu H. Direct evidence for the undulation of the 660 km discontinuity beneath Tonga: Comparison of Japan and California array data. Geophys Res Lett, 1995, 22: 531-534??
[27]  5 Castle J C, Creager K C. Seismic evidence against a mantle chemical discontinuity near depth beneath Izu-Bonin. Geophys Res Lett, 1997, 24: 241-244??
[28]  6 Clooier J D, Helffrich G R, Wood B J. Seismic discontinuities and subduction zones. Phys Earth Planet Inter, 2001, 127: 35-49??
[29]  7 Tajima F, Grand S P. Variation of transition zone high-velocity anomalies and depression of discontinuity associated with subduction zone from the southern Kuriles to Izu-Bonin and Ryukyu. J Geophys Res, 1998, 103(B7): 15015-15036 ??
[30]  8 Brudzinski M R, Chen W P. A petrologic anomaly accompanying outboard earthquakes beneath Fiji-Tonga: Corresponding evidence form broadband P and S waveforms. J Geophys Res, 2003, 108(B6): 2299, doi: 10.1029/2002JB002012
[31]  9 Wang Y, Wen L X, Weidner D, et al. SH velocity and compositional models near the 660 km discontinuity beneath South America and northeast Asia. J Geophys Res, 2006, 111: B07305, doi: 10.1029/2005.JB003849
[32]  22 Schmid C, van der Lee S, Giardina D. Correlated shear and bulk moduli to 1400 km beneath the Mediterranean region. Phys Earth Planet Int, 2006, 159: 213-224??
[33]  25 Wang J, Sinogeikin S V, Inoue T, et al. Elastic properties of hydrous ringwoodite. Am Mineral, 2003, 88: 1608-1611

Full-Text

Contact Us

service@oalib.com

QQ:3279437679

WhatsApp +8615387084133