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Deriving regional vertical fluid migration rates offshore southwestern Taiwan using bottom-simulating reflectors |
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| Authors: | Liwen Chen Wu-Cheng Chi Char-Shine Liu Chun-Tien Shyu Yunshuen Wang Char-Yu Lu |
| Institution: | 1. Institute of Geosciences, National Taiwan University, Taipei, Taiwan 2. Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan 3. Institute of Oceanography, National Taiwan University, Taipei, Taiwan 4. Central Geological Survey, MOEA, Taipei, Taiwan |
| Abstract: | Fluid migration rates are important parameters for understanding the structural characteristics and evolution of the crustal tectonics and hydrocarbon exploration. However, they are difficult to measure on the seafloor. Densely sampled temperature measurements might shed light on our study of the fluid migration rates. In this study, we first use reflection seismic data to derive geothermal gradient patterns at different sub-seafloor depths, then calculated 1D vertical fluid flow models by analyzing the Péclet numbers in the offshore regions of SW Taiwan. We found Péclet numbers ranging from 2 to 5, implying that vertical fluid flow velocities are between 6 and 44 cm/year. Assumed a homogenous permeable layer and no lateral variation of the temperature fields, we analyzed possible errors caused by depth-dependent thermal conductivity and velocity-depth function. They probably cause less than 2 cm/year of errors in the estimated vertical fluid flow rate. In terms of regional fluid flow patterns, we found higher fluid flow rates near the toe of the trench, and a dramatic increase in fluid flow rate when the continental slope of the Chinese passive margin enters into the trench, and reduced fluid flow rates in the hinterland. We propose that this is a new and potentially useful method to derive regional fluid flow rate models for studying geochemical and biological processes in shallow seafloor sediments and the regional hydrological budget. |
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