Stress drop estimates of potentially induced earthquakes in the Guy-Greenbrier sequence

摘要

We calculate corner frequencies and stress drops for 25 potentially induced earthquakes (M(w)2.17-2.57) in the Guy-Greenbrier sequence in the central Arkansas. We use the spectral ratio method, employing highly similar earthquakes as empirical Green's functions (eGfs). We show that multiple eGfs give consistent corner frequency estimates for the same earthquake and find a range of stress drops of 1.02MPa to 42.50MPa with a median of 10.57MPa by using the Brune spectral model and the source parameters given by Sato and Hirasawa []. We also analyze stress drop dependence on the assumed spectral models and source parameters and use a bootstrapping analysis to calculate the uncertainty in corner frequency and stress drop estimates. The Boatwright spectral model leads to lower stress drop estimates than the Brune spectral model due to the limited bandwidth and fixed fall-off rates. We find that the uncertainty in the stress drop of each earthquake is generally much smaller than the range of stress drop estimates. The value and range of these stress drops of the potentially induced earthquakes are similar to tectonic earthquakes in California reported by other spectral ratio studies. Our results highlight the value of spectral ratio analyses of earthquakes in the central United States.