Human-induced earthquakes: E-PIE—a generic tool for Evaluating Proposals of Induced Earthquakes

Abstract

The HiQuake database documents all cases of earthquake sequences proposed on scientific grounds to have been induced by anthropogenic industrial activity. Because these cases range from being highly plausible to unpersuasive, stakeholders have requested cases to be allocated plausibility grades. Since no questionnaire scheme existed that was sufficiently generalized to be applied to the diverse cases in HiQuake, we developed a new scheme for the task. Our scheme for Evaluating Proposals of Induced Earthquakes (E-PIE) comprises nine generalized questions with a simple weighting system to adjust for the variable diagnostic strength of different observations. Results are illustrated using a simple colored pie chart. We describe the E-PIE scheme and illustrate its application in detail using the example cases of the Groningen gas field in the Netherlands, the November 2017 M5.4 Pohang Enhanced Geothermal Systems-related earthquake sequence in South Korea, and the 2001 deep-penetrating bombing of Tora Bora, Afghanistan. To test the performance of E-PIE, five analysts independently applied it to a suite of 23 diverse cases from HiQuake. By far the most diagnostic questions are those concerning spatial and temporal correlations with industrial effects. Other data are diagnostically subsidiary. For individual cases, the agreement between analysts correlated positively with the strength of evidence for human induction. E-PIE results agree well with those from a specialist scheme tailored to fluid-injection cases. Its strong performance confirms its suitability to apply to the entire HiQuake database.