Onset and Cause of Increased Seismic Activity Near Pecos, West Texas, United States, From Observations at the Lajitas TXAR Seismic Array

Abstract

In recent years, numerous small earthquakes have occurred near the town of Pecos in West Texas; however, when this activity began and whether it was caused by increased petroleum industry activity has been uncertain because prior to 2017 there were few permanent seismograph stations in the region. We identify and locate earthquakes using data recorded since 2000 at TXAR, a sensitive 10-station seismic array situated about 240 km south of Pecos. We thus show that in 2007, one earthquake occurred near Pecos, in 2009 several more occurred, and subsequently, activity has increased considerably, with more than 2000 events identified in 2017. A time-of-day and year-by-year analysis identifies geographic areas in West Texas where events are likely to be natural earthquakes and quarry blasts. However, for the Pecos events, annual seismicity rates increase along with annual volumes of petroleum production and fluid waste disposal, suggesting a causal link. Analysis of seismograms collected by the EarthScope Transportable Array indicates that the 2009 earthquakes had focal depths of 4.0-5.2 km below sea level, within or just below strata where petroleum is produced and/or wastewater is injected. The largest earthquake to date had magnitude M L 3.7, but the recent high activity rates suggest that greater magnitudes may be possible. For the years 2000-2017, we provide a catalog of 10,753 epicenters of seismic events recorded at TXAR.

Induced Seismicity in the Delaware Basin, Texas

“…The seismicity rate increase generally follows the increase in WD volumes. Of the 369 M ≥ 2.0 earthquakes identified by Frohlich et al (2019) in our study region during 2009-2017, the regional template matching catalog was only able to identify 130 of these events (~35%); the Frohlich et al (2019) catalog does a superior job of characterizing of the early onset seismicity in the Delaware Basin than the regional template matched catalog generated using ANSS cataloged events. For seismicity represented in the ANSS catalog, template matching produces a comparable result to Frohlich et al's (2019) catalog ( Figure S2).…”

“…Template matching applied to the TexNet catalog produces identifies a larger number of events than Frohlich et al's (2019) catalog ( Figure S2). However, in the high-activity region near and south of Pecos, the Frohlich et al (2019) catalog reports hundreds of seismic events per year during 2010-2014 that template matching using the regional catalog was unable to detect. While template matching can improve the number of detected earthquakes, this is an example of the approach being unable to detect seismicity with magnitudes < M C that have waveforms that are dissimilar from those of cataloged events.…”

“…However, as the regional ANSS catalog has a relatively high Mc ~2.9 (Figure S1 in the supporting information), the improved regional catalog is only able characterize earthquakes similar in character to those limited number of cataloged earthquakes. Frohlich et al () identified 7,514 earthquakes in our study area during 2000–2017 using a 10 station seismic array and produced a catalog with a M C ~1. They demonstrated that seismicity began in the Reeves County area in ~2009 with seismicity rate beginning to increase in our study region (Figure ) in ~2011.…”

Hydraulic Fracturing‐Induced Seismicity

“…Much of the recent seismicity has been located within the extent of the Delaware Basin (Figure 13a). The seismicity rate in the Delaware Basin has increased orders of magnitude over the past decade, particularly in the southern portion of the Basin (Frohlich et al, 2019; Skoumal et al, 2020). No earthquakes greater than 3.0 M had been detected in this area prior to 2015; during 2015–2020, more than 67 earthquakes ( M > 3) occurred, with the largest event being a 5.0 Mw .…”

InSAR Reveals Complex Surface Deformation Patterns Over an 80,000 km2Oil‐Producing Region in the Permian Basin

“…While petroleum production and wastewater injection volumes have been rising throughout the basin, the recently cataloged earthquakes are spatially clustered (supporting information section S1). One significant cluster is near Pecos, TX, where increased seismic activity began in 2009 and climbed to more than 2,000 earthquakes in 2017 (Frohlich et al, 2019). To better understand the causes of these earthquakes and to assess the likelihood of infrastructure damage and safety concerns, the State of Texas funded the Texas Seismological Network (TexNet) to record earthquakes down to M 2.0 across the state since 2017 (Savvaidis et al, 2019).…”