Use uranium series 222 Rn radioactive gas emanometry for detection of rock fractures

In Nuporanga locality (SP) occurred many induced earthquakes along 1970 decade, owing to drilling and exploitation activities of pipe wells that crossed basaltic layers of Parana basin. Since that, seismographs were installed to detect earthquakes and feasible cause of phenomenon. At this work, the objective of radon (222 Rn) gas emanometry was detection and measurement of fractures azimuths near these wells. Emanometry profiles near four wells were made to test the method. In each point of these profiles, were buried accumulation tubes, separated by 5 meters, that accumulated Rn gas exhaled from soil, during 3 days. Using a Lucas alpha scintillation cells, was possible to delineate, surely anomaly regions of Rn gas exhalation, considering counting statistic errors and the noise of measurement systems. The content of U and Th in basaltic layers are negligible and, therefore the emanation rate of Rn from soil should be low. Meanwhile, in some collecting point, the observed value was relatively high, that allowed to infer an probably fracture alignments in directions NE or NW. (author)