Seismological and geodetic constraints on the 2011M_w5.3 Trinidad, Colorado earthquake and induced deformation in the Raton Basin

Abstract

The Raton Basin of southern Colorado and northern New Mexico is an actively produced hydrocarbon basin that has experienced increased seismicity since 2001, including the August 2011 M w 5.3 Trinidad normal faulting event. Following the 2011 earthquake, regional seismic observations were used to relocate 21 events, including the 2011 main shock, two foreshocks, and 13 aftershocks. Additionally, interferometric synthetic aperture radar (InSAR) observations of both the 2011 event and preevent basin deformation place constraint on the spatial kinematics of the 2011 event and localized basin subsidence due to ground water or gas withdrawal. We find that the 2011 earthquake ruptured an 8-10 km long segment of a normal fault at depths of 1.5-6.0 km within the crystalline Precambrian basement underlying the Raton Basin sedimentary rocks. The earthquake also nucleated within the crystalline basement in the vicinity of an active wastewater disposal site. The ensuing aftershock sequence demonstrated statistical properties expected for intraplate earthquakes, though the length of the 2011 earthquake is unexpectedly long for an M w 5.3 event, suggesting that wastewater disposal may have triggered a low stress drop, otherwise natural earthquake. Additionally, preevent and postevent seismicity in the Raton Basin spatially correlates to regions of subsidence observed in InSAR time series analysis. While these observations cannot discern a causal link between hydrocarbon production and seismicity, they constrain spatial relationships between active basin deformation and geological and anthropogenic features. Furthermore, the InSAR observations highlight the utility of space-based geodetic observations for monitoring and assessing anthropogenically induced and triggered deformation.

An Incomplete Inventory of Suspected Human-Induced Surface Deformation in North America Detected by Satellite Interferometric Synthetic-Aperture Radar

“…Further research is needed to determine the reason for the lack of detection. The relatively short ALOS-1 data archive may simply be not sensitive enough to detect the ground deformation-we estimate the precision of our measurements in this active agricultural area to be 3-4 cm/yr, which is in line with estimates of ALOS-1 time series precision in other areas (0.5-0.8 cm/yr in New Zealand [65], 0.5 cm/yr in Colorado [66], 2.4 cm/yr in Central America [47], 2 cm/yr in Mexico and Indonesia [67] and ∼2.5 cm/yr in Java [46]. The low level of ground deformation could be due to characteristics of the groundwater pumping or subsurface geology in Oklahoma (e.g., deep injection in very porous rock overlain by very rigid layers).…”

“…Robust null results for deformation associated with human activities can also provide useful constraints on porosity and rock mechanical structure (e.g., Brady Hot Springs and Desert Peak, for example [69,70]), although the significance of the lack of deformation associated with wastewater injection in Oklahoma and the Raton Basin is still to be determined (e.g., [66]). Unfortunately, InSAR data are not routinely collected in all areas of North America.…”

Myths and Facts on Wastewater Injection, Hydraulic Fracturing, Enhanced Oil Recovery, and Induced Seismicity

“…Correction: Wells injecting under gravity feed (i.e., wells where you can pour fluid down the well without added pressure) increase the fluid pressure within the injection formation and thus can induce earthquakes. For example, the vast majority of wells in the Raton Basin are injecting under gravity feed and have induced an earthquake sequence that is ongoing since 2001 and includes an M 5.3 earthquake and an M 5.0 earthquake (Barnhart et al, 2014;Rubinstein et al, 2014).…”

Temporal variation in the magnitude‐frequency distribution during the Guy‐Greenbrier earthquake sequence

“…Since the first clear observation of induced earthquakes in Rocky Mountain Arsenal, during 1960s [Healy et al, 1968] the occurrence of earthquakes has been linked to fluid injection and particularly an increase in pore fluid pressure [Raleigh et al, 1976]. Since 2010, moderate-sized earthquakes were reported to be associated with fluid injection resulting from recent energy development technologies in the oil and gas industry [Horton, 2012;Gan and Frohlich, 2013;Frohlich and Brunt, 2013;Barnhart et al, 2014]. As a result, there has been a significant increase in the seismicity rate in the central U.S. [Ellsworth, 2013].…”