Hydraulic-Fracturing, Induced Seismicity and the Characteristic Earthquake Hypothesis: Observations and Implications

Date: 4/26/2019

Time: 03:45 PM

Room: Cascade I

The characteristic earthquake hypothesis posits that, over a single complete earthquake cycle, fault systems generate an event with a magnitude near the largest possible for the system. According to this hypothesis, episodic characteristic earthquakes occur more frequently than would be expected based on a Gutenberg-Richter relationship derived from the magnitude-frequency distribution during the interseismic period. Over one or more earthquake cycles, characteristic earthquakes are therefore marked by robust occurrence (i.e. exceeding some level of statistical confidence, such as 95%) of large-magnitude event(s) above the expectation of the maximum-likelihood Gutenberg-Richter distribution. Another hypothesis posits that, within a given region, the observed magnitude-frequency relationship for induced seismicity represents a rate-accelerated version of natural background seismicity. According to this model, the seismic moment release over a given time interval corresponds to the expected seismic moment release that would have occurred naturally, over a much longer time window. In the case of a Gutenberg-Richter relationship, log N=a–bM, this would correspond with a shift in the activity parameter, a, with no change in the bvalue. By analyzing a set of local induced seismicity catalogs acquired during hydraulic-fracturing operations in western Canada, we observe evidence in support of the characteristic earthquake model. If validated, this model has important implications for hazard analysis, since it implies that the frequency of large events may be underestimated by the Gutenberg-Richter relationship derived from low-magnitude seismicity. More generally, if the characteristic earthquake model is more widely applicable to induced earthquake sequences in previously quiescent intraplate settings than active fault systems, it may be that this could provide important clues about the nature of fault nucleation and rupture on well healed faults.

Presenting Author: Nadine Igonin

Authors