Mapping Temporal Stress Evolution in Pawnee and Cushing Oklahoma Using Ambient Noise

Date: 4/26/2019

Time: 06:00 PM

Room: Fifth Avenue

Subsurface injection of saltwater into the Arbuckle group in Oklahoma has produced stress changes which have resulted in increased seismicity in the region. We investigate the temporal evolution of stress using seismic interferometry with ambient noise by exploring the temporal evolution of velocity leading up to the 2016 Mw 5.8 Pawnee and Mw 5.0 Cushing earthquakes. We implement a combination of cross-station and single-station autocorrelation ambient noise cross-correlations to provide a robust analysis of the velocity. We analyze continuous seismic data recorded between 2013-2017 on four stations to document the period leading to the largest earthquakes in the study area by computing noise cross-correlation functions using MSNoise software. Waveform analysis is implemented on the 3 components of each station by performing instrument correction and spectral whitening of one-hour long waveforms in the frequency ranges of 0.01–1.0 Hz, 0.5–1.0 Hz, 1.0–2.0 Hz, and 2.0–4.0 Hz then 1-bit normalized. The temporal variability of seismic velocity is evaluated by measuring the time delay between the 5 and 10-day stack of noise correlation functions and a reference defined by the mean velocity of the hourly noise correlation functions for the period analyzed. Preliminary results indicate a velocity increase in 2013-2014 before the beginning of seismic activity leading to the largest events in the area. The temporal velocity variations correlate positively with the seismicity rate in the area in the 2014-2016 period. Both the velocity increase and seismicity rate may be modulated by increased pore pressure in the area.

Presenting Author: Paul O. Ogwari

Authors