Characteristics of Seismogenic Structures and 3D Stress State of the Delaware Basin of West Texas as Constrained by Earthquake Source Mechanisms

Abstract

Seismicity in the Delaware basin is suggested to be associated with oilfield operations. To better characterize the seismogenic structures revealed by the induced seismicity, in this study we determined source mechanisms for the Delaware basin of Texas and leveraged the obtained source mechanisms to perform stress inversion for evaluating the region’s stress state. Based on the seismogenic patterns and seismicity distribution, we identified seven distinctive seismogenic zones. Within each zone, earthquakes form several parallel-trending linear clusters. Most notably, there is an observable change in the seismicity trend on either side of the basin-bisecting Grisham fault zone. In addition, the extent of hypocentral depths vary drastically across the fault zone, with events located below the basin–basement interface north of the fault zone and more shallowly to the south. We also see spatial variations of source mechanism patterns and the direction of the maximum horizontal stress across the Delaware basin. A vast majority of seismic moment release can be attributed to the basement-rooted tectonic faults in the Culberson–Mentone seismogenic zone. A statistic deficit present in the magnitude–frequency distribution suggests that earthquakes with M_w 3.8–4.7 are needed to fulfill this scaling law. It indicates a strong possibility for future occurrence of earthquakes within this magnitude range.