Injection-induced seismicity in the Raton Basin from 2016-2020

Margaret E. Glasgow, Ruijia Wang, Brandon Schmandt, & Eric Kiser

Submitted August 15, 2020, SCEC Contribution #10661, 2020 SCEC Annual Meeting Poster #053

Wastewater injection-induced seismicity has been active in the Raton Basin for the past two decades, including several M>4.0 normal-faulting earthquakes. To characterize regional fault structures, we systematically analyzed two datasets: 1) an 8-station broadband array recording since mid 2016 with an average station spacing of ~30 km and 2) a 96-node short period array recording for one month (Summer 2018) with <3 km station spacing. A machine learning phase picker (PhaseNet) was adopted to detect phase arrivals followed by an automated method for event association and preliminary hypocenter estimation (REAL). We obtain catalogs with ~36,000 events down to M0 using the broadband stations for the 4-year period and ~10,000 events down to M-2 during the one-month nodal deployment. The earthquake locations are refined based on waveform similarity and differential travel times (GrowClust). The fault structures are also characterized through full moment tensor inversions and first motion analyses.
Previous seismic studies of the Raton Basin using significantly less dense arrays (>70 km station spacing) revealed three dominant N-S striking faults extending ~10–25 km in length located in the central part of the basin. Our integrated node and broadband catalog locations and focal mechanism solutions reveal dozens of short (<3 km) fault segments with a range of strikes from ~NE-SW to NW-SE, mostly located within the basement at depths between 2–6 km. Limited seismicity occurs in the final previously identified region which hosted the largest recent earthquake (Mw 5.3 in 2011), while a new cluster with oblique dip-slip regime is revealed toward the southern side of CO and NM boundary. In addition, new earthquake clusters with increasing seismicity since 2016 near the northeastern edge of the basin may suggest the seismic footprint of wastewater injection is expanding. Despite the induced nature of all clusters, statistical analyses based on space, time, and magnitudes of the seismicity show similar behavior to tectonic sequences. We hypothesize increased injection rates lead to reduced clustering but low injection rates in the Raton Basin, compared to other areas, has led to the observed tectonic earthquake interactions. Overall, detailed fault structures and earthquake cycle statistics inferred from a high-resolution earthquake catalog can serve as an observational base for physics-based mechanical modeling and hazard mitigation in the Raton Basin.

Key Words
induced seismicity, machine learning, wastewater injection

Glasgow, M. E., Wang, R., Schmandt, B., & Kiser, E. (2020, 08). Injection-induced seismicity in the Raton Basin from 2016-2020. Poster Presentation at 2020 SCEC Annual Meeting.

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