Medium and long-term mortality effects of an anthropogenic earthquake: a difference in difference analysis

Abstract

BACKGROUND AND AIM: The moment magnitude (Mw) of 5.4 earthquake occurred in Pohang City on 15 November 2017. The earthquake and its aftershocks caused the most damage in Korea since the seismic observations began in 1905, and were estimated to be associated with a fluid injection activity at the Pohang geothermal plant. The aim of this study is to estimate the medium and long-term mortality effects of the 2017 Pohang City earthquake. METHODS: Mortality and population data were archived from Korean Statistical Office and cause-specific age standardized mortality rates were calculated. We selected Jeonju and Jeju cities as controls, which are similar in population size but located 200km and 370km away from Pohang City. We divided the study period into 45 weeks before (reference) and after (period 1:0-14 weeks; period 2: 15-29 weeks; period 3:30 to 45weeks) the earthquake and used difference-in-difference analysis to estimate how earthquake affect daily mortality rate of Pohang City. RESULTS:Non-accidental, respiratory, and pneumonia morality rates of Pohang City have increased around 10 weeks after the earthquake. Compared to Jeonju City, we found increased risks (RR, 95% CI) of non-accidental (Period 2: 1.12 (0.98, 1.27)) and pneumonia (Period 1: 1.61 (1.11, 2.35); Period 2: 1.71 (1.16, 2.54)) mortalities in Pohang City after the earthquake. Compared to Jeju City, we found increased risks of non-accidental (Period 2: 1.10 (0.96, 1.26)), respiratory (Period 2: 1.47 (1.04, 2.07)) and pneumonia (Period 1: 1.52 (1.01, 2.31); Period 1: 1.64 (1.06, 2.54)) mortalities in Pohang City after the earthquake. The effects were greater in elderly population (aged over 60). CONCLUSIONS:We found increase in non-accidental, respiratory, and pneumonia mortalities in Pohang City after the 2017 earthquake. Follow-up studies with health insurance data of Pohang City residents may confirm our study findings. KEYWORDS: earthquake, mortality, difference-in-difference, anthropogenic, health effect