Sensitivity Analysis of Fault Simulation Parameters for Induced Seismicity due to CO2 Injection
Abstract
Earthquake simulations are performed to generate seismicity catalogs from a fault under two conditions: hydrostatic and elevated pore pressure due to CO2 injection. We use RSQSim (the rate and state earthQuake Simulator from Richards-Dinger & Dieterich, 2012) to model the seismicity. RSQSim uses a rate-and-state law that describes the evolution of the frictional shear strength of a fault under constant-rate tectonic shear loading. The resulting seismicity will depend on fault properties, most of which are poorly known. Therefore we analyze the sensitivity of the simulation outputs to key fault input parameters. We first carry out a total sensitivity analysis to rank the parameters, and then we follow this with detailed individual sensitivity analyses of the top-ranked parameters. The metric used to assess sensitivity is the Gutenberg-Richter (G-R) b-value. We then compare the G-R b-values for the two cases: hydrostatic and injection. Our results demonstrate that the G-R b-value is most sensitive to the A/B ratio. A and B are dimensionless constants in the rate-and-state law whose ranges are derived from laboratory data. Other key parameters approximate elastodynamic processes that are not accounted for in the rate-and-state law itself. Knowledge of these parameters will help focus fault characterization efforts and an understanding of induced events. This research was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 Sensitivity Analysis Workflow a) Evaluation of Total Sensitivity of Multiple Fault Parameters where all 5 parameters are concurrently varied b) Workflow for varying a single fault parameter at a time.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.S33D2446T
- Keywords:
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- 7200 SEISMOLOGY;
- 1822 HYDROLOGY Geomechanics;
- 7290 SEISMOLOGY Computational seismology;
- 1645 GLOBAL CHANGE Solid Earth