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Cross-Examining Methods for Determining Source Mechanisms for Induced Earthquakes in the Permian Basin

Description: 

Establishing the causal link between induced earthquakes and oil and gas operations in the Permian Basin depends on accurately assessing the 3-D distribution of seismic sources and their mechanism. The local recordings of the Texas Seismological Network (TexNet), established in 2017, provide a unique opportunity to determine the source characteristics of induced earthquakes in Texas. As one of the main initiatives of the TexNet, the overarching goal of this study is to identify an optimal approach for the regular and automated determination of source mechanisms using TexNet real-time seismic data. In this study, we implemented waveform moment tensor inversion (MTI) using Gisola to analyze over 150 earthquakes in the Delaware and Midland sub-basins. Gisola utilizes an automated algorithm and conducts a 4-D spatiotemporal MT grid search to determine a preferred solution for the source. We then performed a comparative analysis among reported solutions from various sources (e.g., SLU, rCMT, scmtv, NEIC) to cross-examine the consistency in results. Despite general uniformity among different solutions for the source mechanism, the centroid depths derived from Gisola and scmtv consistently appear shallower than that of other solutions. Differences in solutions may be associated with the choice of frequency range used in the modeling, the resolution of centroid locations, the effect of the velocity model, and/or varying station geometry. We also derived focal mechanisms from the P-wave first-motion polarities using HASH for earthquakes that have sufficient azimuthal coverage. Among the 70 earthquakes examined for initial polarities, 58 yielded solutions with HASH, and 26 of those solutions were non-unique. This study underscores the robustness of Gisola in providing high-quality seismic solutions for a wide range of magnitudes (> 2.2) using TexNet data, offering a valuable contribution to the ongoing efforts to comprehend and address induced seismicity in the Permian Basin.

Session: Induced Earthquakes: Source Characteristics, Mechanisms, Stress Field Modeling and Hazards - I

Type: Oral

Date: 5/1/2024

Presentation Time: 09:00 AM (local time)

Presenting Author: Farzaneh

Student Presenter: No

Invited Presentation: 

Authors