Ultralow velocity in the lowermost mantle beneath northeast Eurasia
碩士 === 臺灣大學 === 海洋研究所 === 97 === Mapping global distribution of ultra-low velocity zone (ULVZ) at the core-mantle boundary is crucial to understanding of mantle dynamics and core-mantle interaction. We analyzed records of two Tibetan arrays, INDEPTHⅢ and HiCLIMB, to search for evidence for the pres...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
2009
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| Online Access: | http://ndltd.ncl.edu.tw/handle/48218151377265009622 |
| Summary: | 碩士 === 臺灣大學 === 海洋研究所 === 97 === Mapping global distribution of ultra-low velocity zone (ULVZ) at the core-mantle boundary is crucial to understanding of mantle dynamics and core-mantle interaction. We analyzed records of two Tibetan arrays, INDEPTHⅢ and HiCLIMB, to search for evidence for the presence of ULVZ. The array-stacked ScP phase from one event in Kurile region exhibits significant energy about 9 s after ScP and a small perturbation about 13 s before ScP. Synthetic waveform experiments show that the post- and pre-cursors to ScP can be modeled as ScsP and SdP with a ULVZ of the following properties: δVP = -10 to -12%,δVS = -30%, δρ= 10%, and thickness D = 60-65 km. The thickness is so far the greatest among all the ULVZs previously identified over the globe. This ULVZ is located at a spot beneath NE Eurasia where the lowermost mantle has never been explored before. The distribution of normal ScP bouncing in the neighborhood constrains the lateral dimension of this ULVZ to be about 200 km.
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