Probabilistic Seismic Hazard Analysis for Induced Seismicity

• Author / Creator

  Reyes Canales, Mauricio

• In recent times, there has been increased seismicity in geologically stable basins in North America, thought to be associated with hydraulic fracturing and/or waste water disposal activities. Induced events could generate a seismic hazard higher than natural seismicity, particularly in areas with small-to-moderate natural background seismicity, leading to increasing concerns for operators, regulators, and the public in general. Therefore, it has been necessary to quantify the seismic hazard related to anthropogenic activities. In this thesis, we develop a Probabilistic Seismic Hazard Analysis to estimate the seismic hazard related to induced seismicity. Some of the main challenges to adapt Probabilistic Seismic Hazard Analysis to induced seismicity include the non-stationary behavior of the induced events, the prediction of future recurrence rates, and determine when seismicity declustering is appropriated for the hazard analysis.
  First, we developed a methodology to compute synthetic earthquake catalogs for non-stationary seismicity using Monte Carlo simulations. We found that the Poisson model remains relevant for analyzing non-stationary induced seismicity. We define non-stationary Gutenberg-Richter parameters to describe time-dependent seismicity rates and to assess the hazard for this type of seismicity. Then, we apply two methodologies to predict the Gutenberg-Richter parameters related to injection-induced seismicity, in particular, temporal changes in the a-values. Our results show that these short-term predictions are able to describe the changes in the overall seismicity patterns within a reasonable level. However, they make inaccurate predictions for specific magnitude ranges, resulting in an under- or overestimation of the hazard, among other things, due to the assumption of unchanged b-values.
  We also identify the cases when seismicity declustering is recommended. If mainshocks and aftershocks have considerably different b-values, declustering leads to improved hazard assessments, since it allows for better estimations of the magnitude-frequency distribution of the largest events. On the other hand, if mainshocks and aftershocks have similar b-values, declustering is not recommended since it eliminates large magnitude events that significantly contribute to the seismic hazard. We also show that assuming Poissonian distributions in hazard predictions does not lead to inaccurate long-term hazard predictions, even if time-varying aftershock sequences are present in the catalog.
  Finally, I describe a methodology to build seismicity scenarios in areas prone to induced earthquakes. This type of scenario building, based on projected operations in susceptible areas to induced seismicity, can give us insights into future seismicity patterns. Building seismicity scenarios is one of the first steps to fully forecast seismic hazard for induced seismicity. I also recommend the assessment of retrospective annual seismic hazard analysis in areas prone to induced earthquakes, like the province of Alberta. These annual seismic hazard assessments can provide useful insights into the temporal evolution of the seismic hazard related to anthropogenic activity.

• Subjects / Keywords

  • Statistical Seismology
  • Probabilistic Seismic Hazard Analysis
  • Earthquake Hazard
  • Induced Seismicity
  • Seismology

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-scg2-r887

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.