Observations of fluid and gas geochemistry for earthquake precursor in Taiwan: Past, recent status and future scenarios

The establishment and development of geochemical monitoring in Taiwan were introduced to present the relationship between geochemical anomalies and major seismicity in order to improve the possibility of forecasting an impending earthquake. From the dataset covering several years of continuously monitored soil gas, some anomalously high radon (Rn) concentrations at specific times were identified using a statistical technique. We found that many Rn anomalies were observed in soil gas prior to the occurrence of impending earthquakes. Each station is sensitive to only the seismic events in its specific surrounding area. Comparing the pre-seismic events at different monitoring stations, we can further identify the sensitivity zone of each monitoring system and then may be able to propose the potential area of the epicenter of the upcoming earthquake. The relative heights of soil gas anomaly at two or more stations of their respective times of occurrence, could eventually enable satisfactorily precise predictions of the ensuring earthquakes in location, time and magnitude. Multi-observations of possible earthquake precursors in the Taiwan area were also further integrated for finding consistent precursors before large earthquake.