Doctor of Philosophy
Atkinson, Gail M.
This thesis characterizes ground motions from induced seismic events in Alberta and Oklahoma, following an overall methodology that uses ground-motion recordings to calibrate the parameters of a seismological model. This body of work is carried out in three related studies.
In the first study, we perform a preliminary evaluation of ground motions in Alberta using thousands of observations of natural, induced and blast events of magnitude 1 to 4, recorded on a newly-deployed regional seismograph array. We evaluate the applicability of a moment magnitude (M) estimation algorithm for the events and compare the observed ground motions with expectations based on regional ground motion prediction equations (GMPEs). Ground motions for earthquakes are similar to those predicted by the small-M GMPE of Atkinson (2015), if one assumes that the predominant site condition in Alberta is a generic soft soil (Vs30 < 400 m/s).
In the second study, ground motion observations from induced seismic events in Oklahoma are used to perform a generalized inversion to solve for regional source, attenuation and station site responses within the context of an equivalent point-source model following the method of Atkinson et al. (2015) and Yenier and Atkinson (2015b). The resolved parameters fully specify a regionally calibrated GMPE that can be used to describe median amplitudes from induced earthquakes in the central United States. Overall, the ground motions for soft rock (B/C) site conditions for induced events in Oklahoma are of similar amplitude to those predicted by the GMPEs of Yenier and Atkinson (2015b) and Atkinson et al. (2015) at close distances, for events of M 4 to 5. For larger events the Oklahoma motions are larger, especially at high frequencies. The Oklahoma motions follow a pronounced trilinear amplitude decay function at regional distances.
In the third study, we follow a similar procedure to develop a GMPE that fully specifies regional source, attenuation and station site responses for induced seismic events in Alberta. Ground motions in Alberta follow a pronounced trilinear amplitude decay function at regional distances. We account for observations of lower amplitude ground motions at high frequencies in Alberta when compared to those observed in Oklahoma by adapting the near surface attenuation kappa effect (κ) model from Hassani and Atkinson (2018). Overall ground motions in Alberta are consistent with those expected for very shallow (depth < 10 km) natural events in central and eastern North America.
Novakovic, Mark, "Empirical Characterization of Induced Seismicity in Alberta and Oklahoma" (2018). Electronic Thesis and Dissertation Repository. 5961.