Structural characteristics of shallow faults in the Delaware Basin

Horne, E. A., P. H. Hennings, K. M. Smye, S. Staniewicz, A. Chen, and A. Savvaidis (2022), Structural characteristics of shallow faults in the Delaware Basin, Interpretation, doi:10.1190/INT-2022-0005.1.
Abstract: 

The Delaware Basin of Texas and New Mexico is experiencing elevated levels of seismicity. There have been more than 130 earthquakes with local magnitudes of at least 3.0 recorded between 2017 and 2021, with earth- quakes occurring in spatiotemporally isolated and diffuse clusters. Many of these events have been linked to oilfield operations such as hydraulic fracturing and wastewater disposal at multiple subsurface levels; however, the identification and characterization of earthquake-hosting faults have remained elusive. There are two distinct levels of faulting in the central region of the basin where most earthquakes have been measured. These fault systems include a contractional basement-rooted fault system and a shallow extensional fault system. Shallow faults trend parallel to and rotate along with, the azimuth of SHMAX, are vertically decoupled from the basement-rooted faults, accommodate dominantly dip-slip motion, and are the product of more recent processes including regional exhumation and anthropogenic influences. The shallow fault system is composed of northwest–southeast-striking, high angle, and parallel trending faults which delineate a series of elongate, narrow, and extensional graben. Although most apparent in 3D seismic reflection data, these narrow elongate graben features also are observed from interferometric synthetic aperture radar (InSAR) surface deformation measurements and can be delineated using well-located earthquakes. In contrast to the basin-compartmentalizing basement-rooted fault system, shallow faults do not display any shear movement indicators, and they have small throw displacement given their mapped length, producing an anomalous mean throw-to-length ratio of 1:1000. These characteristics indicate that these features are more segmented than can be mapped with conventional subsurface data. Much of the recent seismicity in the south-central Delaware Basin is associated with these faults and InSAR surface deformation observations find that these faults also may be slipping aseismically.

PDF of Publication: 
Download from publisher's website.
Research Program: 
Earth Surface & Interior Program (ESI)
Funding Sources: 
This work was supported by the State of Texas through The University of Texas Bureau of Economic Geology (BEG) TexNet Seismic Monitoring and Research Project and the industrial associates of the Center for Integrated Seismicity Research (CISR). J. Chen and S. Staniewicz were supported by the NASA Earth Surface and Interior Program, grant 80NSSC18K0467.