CAREER: Mantle seismic structure beneath North America and evolving seismicity in the Raton Basin

This project will support two lines of research. The first takes advantage of recent and ongoing community-driven collection of broadband seismic data systematically covering more than half of North America. The second focuses on earthquake activity in the Raton Basin, which is on the New Mexico-Colorado border and an area of natural gas production and wastewater injection. Both lines of research include educational opportunities for undergraduate and graduate students as well as outreach activities to improve the representation of Earth science and particularly geophysics in middle schools around Albuquerque. The goals of the first line of research will be achieved by seismic investigation of mantle structure and its implications for thermal and chemical convection processes beneath North America, with particular consideration of potential evidence for or against a substantial geochemical reservoir of water in an unusual layer about 400-700 km deep referred to as the mantle transition zone. The properties of this layer could provide new insights into limits on the evolution of surface water over Earth's history and occurrence of partial melting as a result of ongoing convection. The second line of research will involve collection and analysis of seismic data in the Raton Basin over the duration of this project in order to test how spatial and temporal patterns and mechanisms of earthquakes respond to varying wastewater injection rates, increasing cumulative injected volume, and small natural transient stresses.

This project's two main research goals are: 1) to test the hypothesis that the mantle transition zone beneath North America is a major geochemical reservoir of water and 2) constrain the time dependent response of Raton Basin seismicity to wastewater injection. Both lines of research are integrated with the educational goal of increasing participation in geoscience research among the diverse population of New Mexico students at levels ranging from middle school to graduate school. The first line of research will use a suite of interdependent analyses of EarthScope seismic data including mapping of continuous and laterally sporadic interfaces, mapping variations in the sharpness and amplitude of interfaces, and constraining the influence of 3-D velocity structure on interface imaging. Quantitative assessment of the hydrated transition hypothesis will be conducted through collaborations with mineral physicists and geodynamicists. The second line of research involves extended observation and analysis of seismicity in the Raton Basin, which has hosted an increase in seismicity correlated with increased wastewater injection. This component will enable higher resolution and longer-term observations of feedbacks between seismogenic deformation and wastewater injection. Annual class research projects and undergraduate interns will primarily conduct data collection and analysis to constrain temporal variations in the distribution of active faults, source mechanisms, magnitude distribution, and susceptibility to external triggering. Place-based education efforts at the middle school level, where many students first encounter the geosciences, will use Raton Basin and EarthScope data to enhance exposure to geoscience research and awareness of geoscience career opportunities among underrepresented populations.