Chemical release risk assessment in earthquake: Natech event scenario

In recent decades, an increase in natural disasters has led to the Natech events occurrence, which are technological accidents triggered by natural hazards. This study aims to assess the risk of chemical release of the H₂S toxic gas following an earthquake from the refinery.

The Natech risk assessment was carried out in potential earthquake risk scenarios via a semi-quantitative method using Rapid-N software. The reference scenario was obtained using the Australian SMUG Model, which has presented precise prioritization.

The Natech risk assessment has shown 40 possible earthquake risk scenarios from 5 enclosing Faults in Tehran (North Tehran, Mosha, North Ray, South Ray, and Kahrizak) with an extension of more than 15 km. The earthquake moment magnitudes of 7.5, 7.1, 6.5, and 5.9 were obtained on the Richter scale and at two Focal depths of 5 and 10 km. The South-Ray Fault (HSR-1) was selected as the reference scenario with a moment magnitude of 7.5 on the Richter scale at a Focal depth of 5 km and a distance of 5.5 km from the earthquake epicenter. The highest probability of Natech risk has shown the release of H₂S toxic gas in an area with a radius of 6.59 km from the studied vessel in atmospheric stability conditions.

Legislation in line with risk reduction, planning for the transfer of potentially dangerous industries to outside urban areas, monitoring land use laws, and promoting coordination between the government, industries, and people in the management of risks caused by industries containing hazardous substances and processes, assessing the risk of Natech events and their consequences, strengthening risk communication and the installation of early warning systems, and public education to adopt personal and socially safe behaviors when facing natural disasters are recommended.