頁籤選單縮合
題名 | The Long Wavelength Gravity Field in SE Asia=亞洲東南部之長波長重力場 |
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作者 | Milsom,John; Rocchi,Valentina; | 書刊名 | 中國地質學會會刊 |
卷期 | 41:4 1998.11[民87.11] |
頁次 | 頁489-495 |
分類號 | 350 |
關鍵詞 | 亞洲東南部; 長波長重力場; Long wavelength gravity field; SE Asia; |
語文 | 英文(English) |
英文摘要 | The long wavelength components of the Earth's gravity field can be determined from observations of perturbations in satellite orbits, supplemented by direct measurements of sea surface elevation (the geoid) and conventional gravity data. In SE Asia, as elesewhere, the long wavelength field is strongly correlated with anomalously high seismic body wave velocities in the mantle which are due to the presence of deep subducted lithosphere. Comparisons with the results of seismic tomography indicate that the long wavelength field is influenced most strongly by mass excesses in the lower mantle, i.e. below the 600 km discontinuity. In SE Asia, the gravity patterns suggest that subduction zones formerly existed close to the present-day eastern and possibly western coastlines ob Borneo and that the eastward extension of the active margin of the Eurasian Plate to the Banda Arc is of very recent origin. Strongly positive long-wavelength gravity fields are absent from the Taiwan region, although they reappear farther north in the Japan Sea. Evidently the subducted slab associated with the west-facing Taiwan arc has not yet reached depths at which it can exert a significant influence on the regional gravity field. |
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