The 222 Rn and CO 2 soil gas distribution at Lembang Fault Zone, West Java - Indonesia

Series of Rn measurements had been employed around the Lembang Fault Zone, West Java - Indonesia to investigate its relationship with the fault zone. Furthermore, the mechanism of Rn transport is also investigated by performing soil gas CO and its δ C measurements. The evaluation of Rn concentration shows that 34% data are within threshold values with an average of 14,117 Bq/m , with anomalous concentration greater than 20,000 Bq/m . The concentration of CO in soil gas is varied from 72 ppm to 13,241 ppm and consisted of three populations, with 40% of the data above 655 ppm. The spatial distribution pattern shows that most of Lembang Fault Zone segment coincides with high Rn concentration indicating high permeability zone. Furthermore, the average Rn concentration in western part of the fault is higher than the eastern part and this may be correlated with higher seismic activities. In contrast to Rn, CO concentration shows less correlation to the fault structure. Based on δ C values, the source of soil CO is dominated by atmospheric CO , with minor mixing of biogenic origin. Although Lembang Fault Zone is located in the south of an active volcano, there is no indication of magmatic CO origin. The lack of correlation between Rn and CO suggests that there is no indication of Rn transport by CO as carrier gas.