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The effect of solid-earth tides on earthquake rate in Oklahoma and Kansas

Margaret E. Glasgow, & Justin L. Rubinstein

Submitted September 10, 2023, SCEC Contribution #13052, 2023 SCEC Annual Meeting Poster #024

Natural stress oscillations from Earth’s tides provide short-timescale (e.g., daily and bi-weekly), semi-repeatable tests of fault strength. Given that induced earthquakes are likely occurring in areas that are critically stressed due to high fluid pressures, which may be particularly sensitive to tidal forcing, it is possible that there would be a correlation between Earth tides and induced earthquake rates. We investigate this using a machine-learning-built earthquake catalog from 2010-2020 (Park et al., 2022) that contains ~300,000 events in Oklahoma and Kansas, together with numerical modeling of the solid-earth tides. We use the Schuster’s p-value to test whether there is a statistically significant correlation between the tidal phase and the earthquake rate. Initial analysis reveals a significant correlation (p-value<0.001) between the earthquake rate above the minimum magnitude of completeness and the fortnightly (~two-week) tidal phase. The earthquake rate is lowest at 30-60° following the tidal maximum and highest at 150-180° and -120 to -90° (Figure 1a). In contrast, the correlation between the earthquake rate and the semi-diurnal signal is insignificant (p-value>0.5). We will test multiple declustering methods to determine whether the background seismicity correlates with tidal phase. The amplitude of stress changes due to the solid-earth tides will be compared to those suggested to induce seismicity from hydrologic modeling.

Key Words
tides, induced earthquakes, triggering

Glasgow, M. E., & Rubinstein, J. L. (2023, 09). The effect of solid-earth tides on earthquake rate in Oklahoma and Kansas. Poster Presentation at 2023 SCEC Annual Meeting.

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