Association between Oklahoma earthquakes and anxiety-related Google search episodes

Abstract

Background: Oklahoma has experienced a rise in seismicity since 2010, with many earthquakes induced by wastewater injection. While large single earthquakes have documented mental health repercussions, health implications of these new, frequent earthquakes remain unknown. We aimed to examine associations between Oklahoma earthquakes and statewide anxiety measured by Google queries.

Methods: The U.S. Geologic Survey's Advanced National Seismic System Comprehensive Catalog supplied earthquake dates and magnitudes. We used the Google Health application programming interface to compile the proportion of weekly Oklahoma-based health-related search episodes for anxiety. A quasi-experimental time-series analysis from January 2010 to May 2017 evaluated monthly counts of earthquakes ≥ magnitude 4 (a level felt by most people) in relation to anxiety, controlling for US-wide anxiety search episodes and Oklahoma-specific health-related queries.

Results: Oklahoma experienced an average of two (SD = 2) earthquakes ≥ magnitude 4 per month during the study period. For each additional earthquake ≥ magnitude 4, the proportion of Google search episodes for anxiety increased by 1.3% (95% confidence interval = 0.1%, 2.4%); 60% of this increase persisted for the following month. In months with 2 or more ≥ magnitude 4 earthquakes, the proportion of Google search episodes focused on anxiety increased by 5.8% (95% confidence interval = 2.3%, 9.3%). In a sub-analysis, Google search episodes for anxiety peaked about 3 weeks after ≥ magnitude 4 quakes.

Conclusions: These findings suggest that the recent increase in Oklahoma earthquakes has elicited a psychological response that may have implications for public health and regulatory policy.

Figure 1.

Location of instrumentally recorded earthquakes from January 2010 to May 2017 in Oklahoma. Larger circles denote higher magnitude earthquakes. Data from the U.S. Geological Survey’s Advanced National Seismic System Comprehensive Earthquake Catalog (ComCat; https://earthquake.usgs.gov/earthquakes/search/).

Figure 2.

Distribution of earthquakes and monthly Google searches from January 2010 to May 2017 in Oklahoma. A, Monthly total of ≥M 4 earthquakes. B, Natural log of monthly trend for all Google anxiety-related search episodes in Oklahoma with fitted values from the time series model. Thirteen months of fitted values were lost to modeling. Search probabilities were multiplied by 10 million prior to log transformation for readability.

Figure 3.

Monthly proportion of health-related Google search episodes from January 2010 to May 2017. The green line represents anxiety-focused queries in the United States. The orange line represents similar queries originating in Oklahoma, and the purple line represents Oklahoma search episodes related to toothache. Search proportions were multiplied by 10 million for readability. Both nationwide and Oklahoma-specific anxiety queries trended upwards over time. Beginning in September of 2015, we identified a statistically significant divergence between United States and Oklahoma queries (P < 0.005, single-tailed test), with Oklahoma queries increasing more rapidly.