利用衛星影像探討龜山島周圍海域熱液與地震的關係

龜山島的後火山活動包含熱液和地震，熱液變化可能反應出活動的劇烈程度，所以本研究將地震當作活動指標，比對熱液變化與地震，借此得出熱液變化與火山活動之間的關係。龜山島東側的熱液因含有硫，顏色與周圍海水不同可被衛星影像偵測，衛星影像分析有三個的步驟：(1)去除陸地的千擾；(2)去除雲的干擾；(3)進行影像分類。分類出熱液後，使用相關係數與前後發生的地震比對，共有四種方式(1)熱液面積與地震數量；(2)熱液面積與地震規模；(3)熱液量與地震數量；(4)熱液量與地震規模。結果顯示熱液面積與前後1天和2天有較大的相關，且相較於前幾天的地震，後幾天發生的地震與熱液面積的關聯較大。

關鍵字

龜山島；熱液；地震；光學式衛星影像；影像分類

並列摘要

Guishan Island is located at north eastern Taiwan belongs to Yilan County. According to geophysical and geochemical studies, it is an active volcano, and the latest eruption occurred in the Holocene (7 ka). The active hydrothermal vents and earthquake can be considered as manifestations of volcanic activity. There are some hydrothermal vents at eastern offshore, and the fluids from the vents are mostly made up of sulfur, which cause the discoloration of the ocean around Guishan Island. The discolored area is called plume which can be easily detected by satellite image. The shape and size of plume are disturbed by ocean currents or winds. In this study, we detect the plume area by three steps: (1) remove land area; (2) remove cloud area; (3) classification. First, ENVI is used to build a mask and remove land area. Followed by a fully constrained least squares approach, it is a mixed pixel classification method for concentration estimation in each pixel. Finally, the area of plume is calculated from the result of least square approach, and then compare with the number of earthquake events to find the relationship between them. In our experiment, 36 SPOT images in 2008 are adopted, and the result shows that the larger area of plume was occurred around the large cluster of events. The area of plume is related to earthquake but there isn't clear. After the correlation coefficient is calculated, the highest is in ±1day. It means maybe the earthquakes can cause the area of plume become larger.

並列關鍵字

Guishan Island ； hydrothermal vent ； earthquake ； satellite image ； image classification

國際替代計量

利用衛星影像探討龜山島周圍海域熱液與地震的關係

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