英文摘要 |
Soil-gas emissions along active zones are demonstrated as a geochemical tool to identify and monitor tectonic activity in the region. The present work is focused on Hsincheng fault in Hsinchu area and the Hsinhua fault in Tainan for earthquake monitoring using soil gas method to determine the influence of such formations on enhanced concentrations of different gases in soil to monitor the tectonic activity in the region. Along with some preliminary field surveys in Ilan area in 2008 to find appropriate site for establishing geochemical monitoring station. To carry out the present investigation variation in temporal soil-gases compositions was measured at continuous earthquake monitoring station established along Hsincheng and Hsinhua faults in Hsinchu and Tainan areas, respectively. Observations have shown potential precursory signals for some major earthquakes in the region. Results have shown that Hsinhua and Hsincheng faults have different tectonic settings. Hsinhua soil-gas variations show precursory signals for earthquakes occurring in south or south eastern part of Taiwan , whereas, for Hsincheng fault most of soil-gas variation precursory signals were recorded for the earthquakes that occurred along Okinawa Trough and Ryukyu Trough. Hsinchu monitoring station has shown better confidence level(i.e. 2.8) than monitoring station along the Hsincheng fault, hence seems to be a better station. During the preliminary survey in Ilan area, five profiles has been completed so far in which in about 46 samples were collected and analysed. Distributions of radon values have shown anomalous values along the Nanao fault and other tectonic features.. |