Our earlier study in attenuation, noted as 1/Q, revealed the feature with high attenuation on the hanging wall of the ruptured Chelungpu fault of the 1999 Chi-Chi earthquake, and observed a decreasing in Qs within the fault rupture zone two years following the 1999 Chi-Chi earthquake by Qs tomography images and an analysis of single-path Qs near the Chelungpu fault. The observation of temporal changes in Qs after the Chi-Chi earthquake implies variations of pore fluid saturation in the ruptured fault zone. The reduction in Qs two years following the Chi-Chi earthquake might indicate high pore-fluid saturation within fractured fault zone rocks due to post-seismic redistribution of the fluid. The significant features in this temporal change study was the sudden increase in Qs co-seismically and a transient decay with a diffusion process for hours and days after a larger event (M>6.5). This feature might be associated with the change in permeability which as a consequence of fluid flow migration after an earthquake. Our proposal would like to further pursue this feature to understand the fluid flow behavior right after the earthquake, and the possible association of this feature to the aftershock activity. In addition to that, the subduction zone system had been considered to be involved in a dehydration process, which might be associated with the seismicity. The dehydration system involved three lines for the distance from the subduction slabs (Tanaka, 2014, personal communication). The southwestern Taiwan as a subduction system of Manila Trench close to inland Taiwan, it might be the possible region to examine this first dehydration line of a subduction system. In this proposal, we would also work closely with Prof. Tanaka of University of Tokyo to combine their observations through geochemistryand our observation through geophysics to understand the possible fluid migration system within the first dehydration line. In the first year, we estimated the possible fluid content in the fault zone, and further analyze the P and S wave spectra to give the hint on the possible indication on fluid migration triggered earthquakes. For the 2nd year project, we will continue the effort to give an overall understanding on the fluid migration system and its association to earthquake triggering.
|Effective start/end date||1/08/16 → 31/07/17|
UN Sustainable Development Goals
In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This project contributes towards the following SDG(s):
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