Microseismicity Observation and Characterization at Cape Modern and Utah FORGE

Abstract

To prepare the new stimulation and exploration of geothermal resources at Cape Modern, Utah, we deploy seismometers, test noise level, and refine velocity models. Shallow boreholes (a few tens of meters) help to improve the signal-to-noise ratio. We numerically simulate seismic wavefields generated by microseismicity using a realistic velocity model and noise level to understand our monitoring capabilities. Background seismicity ratio before stimulation with the new seismometers will be discussed. Also we revisit stimulation data at Utah FORGE to develop a method to better characterize microseismic events. A few deep borehole geophones can detect small events very well, but because of the limited coverage of the aperture, estimation of focal mechanisms is challenging. The surface nodal sensors are useful to compensate the aperture coverage but only for larger events. We will present focal mechanism estimation for smaller events by combining both surface and deep borehole measurements. These methods can be used for stimulation at the Cape Modern site to better characterize small events.