Landsat 7 Etm+ On Geothermal Exploration

Geothermal Anomaly Mapping Using Landsat ETM+ Data in Ilan Plain, Northeastern Taiwan HAI-PO CHAN, CHUNG-PAI CHANG, and PHUONG D. DAO

Aisya Nur Hafiyya K. || 03411640000032

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geophysical methods are limited to the scope of prospecting because of the operation cost and site reachability in the field.

Aim to apply and integrate thermal infrared (TIR) remote sensing technology with existing geophysical methods for the geothermal exploration in Taiwan. 3

Method Thermal Infrared (TIR) : to retrieves land surface temperature and thermal anomaly using Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) imagery 4

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Why Ilan Plain? ⪢ Taiwan is located in the Pacific Rim of Fire, thus possesses rich geothermal resources from volcanic activities of the plate convergence ⪢ Ilan Plain is a geologically active area affiliated with the Okinawa Trough. ⪢ The area is mainly covered by Oligocene to Miocene rocks (shale and sandstone in the main) and quaternary alluvial deposits. ⪢ Evaluated thermal gradient of 30 water wells 6

Geothermal System Identification

From a several geophysical methods conducted in Ilan Plain, concluded: ⪢ The high heat flow and geothermal gradient are caused by the presence of a magma chamber in the shallow crust and shallow intrusive igneous rock. ⪢ Geothermal fluid was heated by the hot rock in Chingshui geothermal field ⪢ Geothermal reservoir of Chingshui is likely linked with Chingshuihsi fracture zone. 8

Methodology

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Main Process

LS TP rof ile

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Pr Data oc ess ing

Landsat ETM + data

Using MODTRAN

Using MODTRAN

Using Plank Function 11

the Use of :

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Thermal Bands

Near-Infrared Bands

To retrieve the temperature of subsurface

To retrieve the surface data (vegetation, drought areas, etc)

Retrieved LSTs Ilan Plain

Thermal Band 13

Near-Infrared Band

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LST compared with fault structure and depth contour

Discussion ⪢ The pattern of thermal anomaly is consistent with those presented in the previous studies (Chiang et al. 1979, 2007) ⪢ the features beneath the plain are not much investigated due to the thick sediment deposit. ⪢ spatial correlations between thermal anomalies and faults for areas near mountains is more significant than areas near the plain center ⪢ Results indicate that area A, E, and F are three sightseeing geothermal landscapes where hot springs and hydrothermal explosions are widely distributed. 15

LST x MT comparing LST profile to a geophysical method

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LST profiles compared with MT resistivity section of profile A and profile B from Tong et al. 2008. The low-resistivity zones identified in the resistivity sections (c, d) are echoed in the LST profiles (a, b)

Discussion ⪢ The significant low-resistivity zones observed in the resistivity sections (Fig. 14c, d) are echoed with the lowtemperature zones of LST profiles ⪢ The low-resistivity zones in the resistivity sections contain rocks with higher porosity and permeability, and water saturation (amount of water), may subsequently lead to the lower temperature on LST. 18

*) Previous MT surveys in the study area show that conductive structures with significant low-resistivity (less than 100X-m) usually were identified as the fracture zone

Conclusion • the occurrences of hot springs and geothermal drillings are in close agreement with anomaly areas. • Thermal anomaly patterns indicate that the distributions of geothermal areas appear correlating with the development of faulted structures in Ilan plain.

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