Source Complexity of the 2015 Mw 4.0 Guthrie, Oklahoma Earthquake

Qimin Wu, Xiaowei Chen, & Rachel E. Abercrombie

Under Review April 8, 2019, SCEC Contribution #9038

We demonstrate the complex source process of a potentially induced Mw 4.0 earthquake near Guthrie, Oklahoma. Relative source time functions (RSTFs), retrieved using a time-domain empirical Green’s function (EGF) deconvolution method, show clear evidence of rupture complexity with the presence of multiple pulses and systematic azimuthal variations. Directivity analysis reveals a well-defined rupture propagation at ~120º toward the southeast. Detailed modeling of the RSTFs results in a four-subevent model spanning ~1 s in time and ~1.5 km in space, in which the earthquake ruptured four successive slip episodes unilaterally to the southeast. Multiple-EGF spectral ratio analysis also shows significant complexity as evidenced by azimuth-dependent deviations from the omega-square (Brune) model. The observations of the concentration of early aftershocks at the periphery of the inferred rupture model along the rupture direction and amplified ground motions at stations to the southeast can both be well explained by the directivity effect.

Wu, Q., Chen, X., & Abercrombie, R. E. (2019). Source Complexity of the 2015 Mw 4.0 Guthrie, Oklahoma Earthquake. Geophysical Research Letters, (under review).