To heal or not to heal?: The moment-recurrence time behavior of repeating earthquakes in the 2011 Prague, Oklahoma aftershock sequence is consistent with laboratory healing rates

Kristina K. Okamoto, Heather M. Savage, Emily E. Brodsky, Elizabeth S. Cochran, Rachel E. Abercrombie, & Brett M. Carpenter

Published September 10, 2023, SCEC Contribution #13110, 2023 SCEC Annual Meeting Poster #132

The competition between fault healing (i.e., re-strengthening) and fault loading determine the seismic cycle. Therefore, understanding how faults strengthen (or weaken) in between slip events is crucial in determining where and when faults experience earthquakes both in tectonic and induced settings. In the lab, frictional healing can depend on factors such as lithology, sliding velocity, stiffness, normal stress, pore fluid pressure, and pore fluid chemistry. At the seismic scale, repeating earthquakes can give observational estimates of fault healing rates; however, linking this healing to lab experiments is difficult because lithology at depth is not well known. Here, we study the 2011 Prague, Oklahoma earthquake sequence which includes repeating earthquakes located in the Arbuckle formation and the granitic basement. We find three spatially distinct groups of repeating earthquakes that suggest different healing behaviors. We interpret these groups as representing 1) stagnant healing in the Arbuckle formation, 2) chaotic healing/loading at the intersection of the foreshock-mainshock fault, and 3) typical log time dependent healing behavior outside of the foreshock-mainshock fault intersection.

We performed friction experiments on the two main earthquake-bearing lithologies at confining pressures representative of the observed earthquake depths, and pore pressures ranging from 0 to 80% of the confining pressure. We measured frictional healing by executing slide-hold-slide tests with hold times ranging from 3 s to 3000 s. The experiments on the basement granite show typical log time healing except at the highest pore pressures where healing behavior was more chaotic, possibly due to anelastic behavior during the hold as shown by in situ displacement data. The Arbuckle dolomite exhibits decreased healing at high pore pressures, with a negative healing rate (weakening) at the highest pore pressure. We suggest that this may be due to an increase in dissolution of dolomite at high pore pressures due to a greater availability of pore fluid. We find that this laboratory understanding of healing behavior at different pore pressures is able to explain the moment-recurrence time behavior of the repeating earthquake families in the Prague earthquake sequence.

Citation
Okamoto, K. K., Savage, H. M., Brodsky, E. E., Cochran, E. S., Abercrombie, R. E., & Carpenter, B. M. (2023, 09). To heal or not to heal?: The moment-recurrence time behavior of repeating earthquakes in the 2011 Prague, Oklahoma aftershock sequence is consistent with laboratory healing rates. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)