Investigation of the effect of earthquakes on indoor radon concentration: The case of Kahramanmaraş

On February 6, 2023, a major seismic activity was observed on the East Anatolian Fault Line. The Pazarcık and Elbistan districts located within the borders of Kahramanmaraş province were affected by two powerful earthquakes with magnitudes of 7.7 and 7.6, respectively. These major earthquakes continued with aftershocks. On February 20, 2023, another earthquake with a magnitude of 6.4 occurred in the Yayladağı district of Hatay province. This study aimed to investigate how radon gas concentrations in indoor environments change with earthquakes and subsequent aftershocks. Radon gas may increase its release to the ground surface due to structural changes that may occur in the earth's crust after earthquakes, and this situation may pose a significant environmental risk to public health. Within the scope of the study, passive radon gas measurements were carried out in indoor areas using CR-39 radon detectors in two periods between February 25, 2023 and July 9, 2023 and August 1, 2023 and December 19, 2023. As a result of the measurements made in the first stage, average radon concentrations of 139 Bq/m³ were found in Hatay province, 61 Bq/m³ in Adana province and 89 Bq/m³ in Gaziantep province. As a result of the measurements made in the second stage, average radon levels of 60, 51, 33, 38 and 39 Bq/m³ were measured in Şanlıurfa, Malatya, Adıyaman, Kahramanmaraş and Gaziantep provinces, respectively. When the measurement results between the two stages were averaged, the average radon concentration in the region was found to be 64 Bq/m³. Based on this radon level, the annual effective dose equivalent was calculated as 1.61 mSv. Since sampling could not be done at the same addresses in both stages in other provinces except Gaziantep, it is difficult to evaluate the effect of the earthquake on radon concentrations in these provinces. However, in the evaluation made specifically for Gaziantep, it is noteworthy that the value of 89 Bq/m³ measured in the first stage decreased to 39 Bq/m³ in the second stage. In the first stage, radon concentrations were measured in the range of 100-301 Bq/m³ at 9 different addresses in Gaziantep, and a value of 1023 Bq/m³ was reached at one address. These values are above the average of 50 Bq/m³ determined by TAEK for Gaziantep in 2014, and can be attributed to the earthquake's slightly increasing effect on the indoor radon concentration in Gaziantep. Similarly, the value of 437 Bq/m³ measured at an address in the first stage in Hatay province was observed to be significantly higher than the average value of 50 Bq/m³ determined by TAEK for Hatay, while the value of 239 Bq/m³ in Malatya province in the second stage was observed to be significantly higher than the value of 48 Bq/m³ determined by TAEK for Malatya.