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The Minimal Effect of Solid-Earth Tides on Earthquake Rate in Oklahoma and Kansas

Description: 

Natural stress oscillations from Earth’s tides provide short-timescale, semi-repeatable tests of fault strength. Given that induced earthquakes occur along critically stressed faults due to high fluid pressures, it is possible that there would be a correlation between the small stress changes imposed by Earth tides and induced earthquake rates. We investigate this using a machine-learning-built earthquake catalog spanning 2010-2020 (Park et al., 2022) that contains ~300,000 events in northern Oklahoma and southern Kansas and numerical modeling of the solid-earth tides. We use Schuster’s p-value to test whether there is a statistically significant correlation between the semidiurnal tidal phase and the earthquake rate. Schuster’s test assumes that each earthquake is independent; therefore, we declustered the earthquake catalog using three approaches (Reasenberg, nearest-neighbor distance, and phase bin method). For all three declustered catalogs, we found that the ~3 kPa volumetric stress change from solid Earth tides does not significantly (p-value>0.05) affect the earthquake rate when the full study region and ten year time period were considered. We tested the effect of the tides on various space discretization and time windows of the earthquake catalog and generally observed a minimal effect of solid Earth tides on the earthquake rate, often less than that expected by random chance (5 %). Preliminary results for the spatial variations in tidal triggering from 2015-2017 reveal 6 % (3 out of 47) of the 20x20 km cells are significantly correlated to the solid Earth tides. Two of the three cells are in close proximity to regions with high rates of wastewater injection. Of particular interest is the region near Cushing, Oklahoma which has a p-value of 0.002 and an elevated earthquake rate from -120 to 90 phase angle. This area is in close proximity, ~15 km, to the largest total volume of wastewater injection, ~500 M barrels injected by 2017.

Session: Induced Earthquakes: Source Characteristics, Mechanisms, Stress Field Modeling and Hazards [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Margaret

Student Presenter: No

Invited Presentation: 

Authors