Earthquake Disaster Fatality Data: Temporally Stable Power Law Behavior and Effects of Underreporting

Abstract

We investigate changes in the global reported fatalities from earthquake disasters in the global Emergency Events Database (EM-DAT). Drawing parallels with the Gutenberg–Richter frequency–magnitude analysis, in terms of disaster frequency versus the number of casualties, we see a significant overlap of the curves and improving levels of completeness over six 20-year periods. This implies a decrease in underreporting with time. We find that the apparent strong upward trend in the number of (reported) earthquake disasters in EM-DAT is caused by a gradually improved reporting primarily of events killing fewer than 10 people. Our findings imply that the true (reported and unreported) number of earthquake disasters, according to the EM-DAT definition, has been surprisingly constant over, at least, the last 100 yr. We also show that the average annual number of people killed in earthquake disasters is relatively unaffected by spurious trends in reporting and has remained remarkably constant despite population increase. This implies an impressive reduced mortality risk roughly proportional to population increase since 1900. However, there is no indication in the data that the risk of future mega-disasters is negligible, and further major reductions in vulnerability should be actively pursued.