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Session: Earthquake Source Parameters: Theory, Observations and Interpretations [Poster]

Type: Poster

Date: 4/25/2019

Time: 06:00 PM

Room: Fifth Avenue

There has been elevated earthquake activity in the Permian Basin since 2008. Previous studies had suggested a link between hydrocarbon extraction, waste-water disposal, and increased seismicity for parts of West Texas. In 2015, a statewide seismic network known as TexNet has been established to monitor the earthquake activities. To date, there has been over seven thousand small earthquakes (ML<3) reported by TexNet across the state of Texas. In the Permian Basin, these earthquakes are unevenly distributed throughout the basin, often occurring in clusters. One of the main tasks of TexNet is to determine earthquakes' source mechanisms on a daily basis. In general, there is no uniform focal mechanism pattern for the Permian Basin as a whole. However, the source mechanism patterns shift from normal faulting in the Midland Basin to a mixed strike-slip and vertical-dip-slip faulting in the Delaware Basin. In the Delaware Basin, these clusters are interpreted to delineate well-oriented basement-rooting faults, which have formed as a result of the accumulation of several extensional and compressional deformation events since the Proterozoic. A vast majority of events that have been located are shown to occur below the sediment interface, corroborating the interpretation of modern reactivation along preexisting basement-rooting faults. Further integration of seismicity, source mechanisms and available geologic data, have resulted in the generation of a new 3D structural framework of the Delaware Basin. This framework has enabled basin-scale fault characterization to better understand potential controlling fabrics that affect local stress-states. First-order observations from this model highlight areas where heterogeneities in source mechanisms may be due to preexisting, basement-rooting fault patterns while the primary structural is a NW-SE oriented high-angle thrust fault. Secondary features include fault-propagation folds and smaller scaled oblique-slip sub-vertical fault zones that trend WNW-ESE. They are likely to accommodate normal and transtensional reactivation.

Presenting Author: Dino Huang