SES-04. Statistical understanding of injection-induced earthquakes in Raton Basin, Colorado & New Mexico

Abstract
Recent research has linked wastewater disposal injection wells to human induced seismicity (Nakai et al., 2017). In the Midwestern United States from 2010 to 2015 an increase in earthquakes shook the nation in places that previously had low temporal and spatial earthquake occurrences. For over a decade, the Raton Basin, which borders Colorado and New Mexico, has had large volumes of fluid pumped from and injected into the subsurface as well as increased earthquake occurrences (Rubinstein et al., 2014). A location such as this provides a long history of well-documented earthquakes allowing for a better understanding of induced earthquake occurrence through statistical analysis methods (Wang et al., 2020). These earthquakes pose a hazard to local residents and create challenges for energy production. This research aims to understand how the regional seismicity is changing due to subsurface processes and stress changes and how these mechanisms drive induced seismicity. We apply the Gutenberg-Richter (GR) Law to describe the relationship between the frequency of occurrence and magnitude of earthquakes by calculating a b-value to help predict how often earthquakes occur (Gutenberg and Richter, 1944). In order to confidently estimate the b-value for a catalog we employ the Thirumalai-Mountain (TM) metric to identify the equilibrium property of ergodicity in order to know if the earthquakes’ spatial or temporal average have been changing with time (Tiampo et al., 2007). Here we show that by employing the TM metric we are able to use the associated effective ergodicity to explain the variations in the catalog data and increase our confidence in other statistical calculations such as the GR b-value. We anticipate our findings will be integrated into hydromechanical modelling and provide a scientific basis for guiding injection operation in a way that reduces earthquake occurrence, so that local residents, energy producers, and policy makers are aware of the impact and can therefore adjust their future actions.