Pecos Array in West Texas: The Importance of Local Arrays in Identifying and Monitoring Induced Seismicity in Complex Areas

Session: Mechanisms of Induced Seismicity: Pressure Diffusion, Elastic Stressing and Aseismic Slip
Type: Oral
Date: 4/29/2020
Time: 09:00 AM
Room: 215 + 220
Description: 

Within the last few years, there has been a notable increase in seismicity in the Pecos, TX region of the Delaware Basin. Since the beginning of 2018, the Texas Seismological Network (TexNet) has recorded 3 M3.0+ earthquakes and ~241 M2.0-2.9 earthquakes in the Delaware Basin.

TexNet and the University of Texas at El Paso are collaborating to improve earthquake location accuracy with a network of 25 3-Component Magseis Fairfield Z-land 5-Hz geophones deployed in the Pecos region since November 2018, known as the Pecos Array. We identify a minimum of 200 events per month with magnitudes as low as M-3. However, only events of M0.3 and above, 88% of the total population, can be properly located.

Using a 1D earth model for the Delaware basin (Savvaidis et al., 2019), the hypocenter depth of the events below an area up to 12 km radius from the Town of Pecos City, using the Pecos array, vary from about 1 to 7 km below mean sea level (msl). The average depth is 3 km and 1σ is 1km. The surface elevation of Pecos is ~0.8km.

Lomax and Savvaidis (2019) improved earthquake depth estimates using probabilistic proxy ground truth (PPGT) station corrections for the TexNet catalog around the Town of Pecos City. In a similar manner, using the local array earthquake locations as proxy ground truth and a 3D earth model for the Delaware basin, we calculate station correction for all TexNet stations in the area which we use to relocate the earthquakes from January 1st 2017 onwards. In this way we improve hypocenter depth estimations for the Pecos area for time spans other than the short duration of the Pecos Array deployment. Additionally, with the Pecos Array data, we perform further, detailed location analyses to constrain whether the earthquake depths are closer to water disposal or hydraulic stimulation and in which geologic unit(s) they occur.

The Pecos Array earthquake data enable more accurate location results, improve understanding of the seismicity patterns around the Town of Pecos City and form a rich basis for study of mechanisms of induced seismicity.

Presenting Author: Alexandros Savvaidis

Authors