Shih-Jung Lin

Geochemical variation of soil–gas composition for fault trace and earthquake precursory studies along the Hsincheng fault in NW Taiwan

The present study is proposed to investigate geochemical variations of soil-gas composition in the vicinity of the geologic fault zone of Hsincheng in the Hsinchu area of Taiwan. Soil-gas surveys have been conducted across the Hsincheng fault, to look for the degassing pattern of this fault system. During the surveys, soil-gas samples were collected along traverses crossing the observed structures. The collected soil-gas samples were analysed for He, Rn, CO(2), CH(4), Ar, O(2) and N(2). The data analysis clearly reveals anomalous values along the fault. Before selecting a monitoring site, the occurrence of deeper gas emanation was investigated by the soil-gas surveys and followed by continuous monitoring of some selected sites with respect to tectonic activity to check the sensitivity of the sites. A site was 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 at Hsinchu National Industrial Science Park (HNISP) in October 2005. Preliminary results of the monitoring station have shown possible precursory signals for some earthquake events.

Radon-thoron monitoring in Tatun volcanic areas of northern Taiwan using LR-115 alpha track detector technique: Pre-calibration and installation

In the present study, experiments have been carried out to calibrate LR-115 alpha detector films in bare and cup-mode exposure for the measurement of radon and thoron concentrations in soil gas. Results showed non-uniformity in track formation on the films in bare-mode exposure. However, in cup-mode exposure the non-uniformity was reduced to a greater extent. The calibration factors obtained for radon in bare- and cup-mode exposures are 0.049 and 0.034 tr. cm−2 per Bq m−3 d, respectively. An attempt has been made to calibrate the radon-thoron discriminative cup with LR-115 films for simultaneous measurements of radon and thoron. This paper also presents the preliminary results of radonthoron monitoring in Tatun volcanic areas of northern Taiwan for the first time using radon-thoron discriminators with LR-115 films. The results show that the safe temperature to install the LR-115 films in volcanic areas is ≤ 65°C and thoron concentration in the study area is low.

Performance comparison of electronic radon monitors

The electronic radon monitors are noted for their convenience and acceptable accuracy. Even so, it is necessary to reassure their data quality regularly. We utilized a performance comparison system for this purpose. The instruments in our laboratories (Alphaguard, RAD7, RTM-2100 and Safety Siren) were tested via the comparison experiments. We conclude that by utilizing this system with the concept of calibration factor, it can be helpful to decide whether to send the monitors back to the original manufacturers for adjustment.