| 英文摘要 |
The present study is proposed to investigate geochemical variations of soil-gas composition in the vicinity of geologic fault zones of Hsincheng fault and the Hsinhua fault within the Hsinchu and Tainan areas, respectively, and to determine the influence of such formations on enhanced concentrations of different gases in soil. Soil-gas surveys have been conducted across the Hsinhua fault, to find out the regional activity of this fault system. During the surveys soil-gas samples were collected along the 13 traverses crossing the observed structures. The collected soil-gas sample bags are analyzed for He, Rn, CO2, CH4, Ar, O2 and N2. The data analysis clearly reveals anomalous values along the fault. The consistency of this pattern confirms that soil-gas can act as a powerful tool for the detection and mapping of active fault zones. Before selecting a monitoring site, the occurrence of deeper gas emanation is investigated by the soil-gas surveys and is followed by continuous monitoring of some selected sites with respect to tectonic activity to check the sensitivity of the sites. A site is selected for long term monitoring on the basis of coexistence of high concentration of helium, radon and carrier gases and sensitivity towards the tectonic activity in the region. A continuous monitoring station was established in October, 2005. Preliminary results of the monitoring station show that the site is good for earthquake monitoring as the soil-gas variations have shown good correlation with impending earthquakes of 26th December, 2006 having local intensity of 4. Geochemical monitoring at the established earthquake monitoring station along the Hsincheng fault has shown potential precursory signals for some earthquakes that occurred in the region. |
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