Structure and Stress-Induced Anisotropy in the Central USA Spatial Variations of Shear Wave Splitting Measurements From Nine Years of Data

Session: Crustal Stress and Strain and Implications for Fault Interaction and Slip [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The state of Oklahoma has experienced significant seismicity rate fluctuations over the last decade, mostly due to anthropological activities like wastewater disposal and hydraulic fracturing. We use the shear wave splitting (SWS) technique to measure SWS parameters (fast direction [φ] and delay time [dt]) to execute a spatiotemporal analysis of the fast direction of polarization (φ) in the central U.S.A (Oklahoma and Southern Kansas). We used 33,367 local earthquakes recorded from 2010 to 2019 by 247 seismic stations from the Oklahoma Seismic Network (OK), the Oklahoma Consolidated Temporary Seismic Network (O2) and the US Geological Survey Network (GS). We used the automated SWS software MFAST (Multiple Filter Analysis Splitting Technique) to calculate the SWS parameters. We successfully calculated 524,395 SWS parameters of which 409,834 parameters are high-quality. The resulting high-quality measurements provide a complete regional dataset of SWS measurements for the Central U.S.A. All stations in the study area show a preferred direction of fast polarization (φ); however, many stations show the presence of a second preferred direction of polarization. The presence of these secondary directions of fast polarization are potentially caused by small local stress perturbations. Additionally, at most stations, either the primary or secondary directions of fast polarization (φ) are consistent with the maximum stress orientation (SHmax) in the study area. However, many regions show a clear deviation between the fast directions of polarization (φ) and SHmax directions. These discrepancies are potentially caused by local structures or pore pressure changes caused by hydraulic fracturing operations.

Presenting Author: Angie D. Ortega Romo

Authors