| Summary: | 碩士 === 國立中央大學 === 遙測科技碩士學位學程 === 106 === Simeuleu island is one of the islands closest to the epicenter of 2004 Indian Ocean Earthquake. This event is known to cause severe land vertical motion in several countries, such as India, Thailand and Sri Langka. This event had changed the coastal topography that can be seen from the uplift of coral reef. In this study, we aim to investigate land vertical motion in Simeuleu island by employing optical remote sensing imageries and a tide model. A series of Landsat images are collected to detect coastal uplift/subsidence. Landsat surface reflectance (Level 2) of pre-event and post-event are collected to conduct pan-sharpening for increasing spatial resolution of green and mid-infrared band. Next, we calculate the modified normalized difference water index (MNDWI) to identify water and non-water for all images and sum up those images to make an inundation chance. Furthermore, we run the NAO.99b tide model to obtain the mean higher high water (MHHW) and mean lower low water (MLLW) as height references. Finally, the inundation chance with the MHHW and MLLW is linearly inverted to obtain a DEM. To observe the changed region, we divide the image set into two epochs before and after the earthquake. Our result shows that the island experiences uplift in the Alafan at about few tens of centimeters while in the southeast experience subsidence about 34 cm. Some particular spots have obviously stronger uplift at around 40 cm.
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