Title: Detection of space-time clusters for radiation data using spatial interpolation and scan statistics
Authors: Fumio Ishioka - Okayama University (Japan) [presenting]
Koji Kurihara - Okayama University (Japan)
Abstract: On March 11, 2011, a massive amount of radioactive material was released into the environment because of the Fukushima Daiichi Nuclear Power Station (NPS) accident. Surveys on the amount of radioactive materials are very important for assessing the state of the surrounding environment and planning future countermeasures. We attempt to detect a high-contaminant cluster accompanied by a time change for the area of evacuation in the Fukushima Prefecture from January 10-19, 2013. The data were air dose rate measured by monitoring post. As a priori analysis, we apply a spatial interpolation using ordinary kriging, because the observations obtained were very sparsely scattered and had extremely large dispersion and bias. The result of applying a spatial scan statistic based on echelon analysis was the detection of a significant space-time cluster that decreased with the passing of time. Moreover, the detected cluster was located in the direction of northwest from the NPS.