Continuous temporal soil-gas composition variations for earthquake precursory studies along Hsincheng and Hsinhua faults in Taiwan

Measurement of soil-gas emissions along active zones is demonstrated as a geochemical tool to identify and monitor tectonic activity in the region. 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 to monitor the tectonic activity in the region. To carry out the present investigation temporal variation in soil-gases compositions was measured at continuous earthquake monitoring station established along the above said faults. 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.