Temporal Correlation Between Seismic Moment and Injection Volume for an Induced Earthquake Sequence in Central Oklahoma

Abstract

The rapidly increased earthquake rate in the central United States has been linked with wastewater injection. While the overall understanding appears clear at large scales, the interaction between injection and faulting at smaller scales within individual sequences is still not clear. For an earthquake sequence in central Oklahoma, we conduct finer‐scale analysis of the spatiotemporal evolution of seismicity and pore pressure modeling. The pore pressure modeling suggests that nearby wells show much stronger correlation with earthquake sequence evolution. Detailed temporal analysis found correlation between earthquake rate, seismic moment, and injection rates from wells in close proximity. However, the observed maximum magnitude (Mmax) is about 1 order of magnitude smaller than expected based on a theoretical relationship between Mmax and cumulative volume. This discrepancy may point toward additional parameters, such as fault size and stress, which influence Mmax. The lower Mmax is consistent with the truncated Gutenberg‐Richter distribution observed from matched filter detected catalog. Overall, the detailed observations suggest that it is possible to resolve relationships between individual disposal wells and induced earthquake sequences.

Source Complexity of the 2015 Mw 4.0 Guthrie, Oklahoma Earthquake

“…Both the RSTFs and the near‐source displacement records suggest the presence of four subevents (Figures and S6). All the subevents are located relative to the hypocenter relocated by Chen et al (). The initial guesses for the subevent locations and times are based on a grid search location method, similar to López‐Comino and Cesca (), using the measured time delays in the directivity analysis (Figures and S9).…”

“…Like other earthquake sequences in Oklahoma, the Guthrie sequence exhibits more swarm‐type behavior than a typical foreshock‐mainshock‐aftershock sequence (Figures c and d). The earthquake sequence shows overall temporal correlation with injection rates from nearby wells (Chen et al, ), but the heterogeneity of the fault zone structure and earthquake focal mechanisms implies possible complex triggering and rupture processes. We download waveform data for all stations within 150 km from the Incorporated Research Institutes of Seismology data management center for the Mw 4.0 (M L 4.3) mainshock and over 20 potential EGF events with M L between 2.3 and 3.3 located within 2 km of the mainshock (Figure ).…”

“…Although it is generally accepted that stress perturbation caused by large‐scale wastewater injection into the Arbuckle Group leads to the reactivation of preexisting faults and stimulates the occurrence of earthquakes, the details of the triggering mechanism that drive individual earthquake sequences are still not well understood. High‐resolution earthquake relocations and focal mechanisms reveal complex basement fault systems that show poor correlation with previously mapped faults (Chen et al, ; McNamara et al, ; Schoenball & Ellsworth, ). In addition to the stress changes from injection, stress interactions between earthquakes, even at small magnitudes (M < 3), contribute to spatiotemporal evolution of seismicity by static and/or dynamic stress triggering (Brown & Ge, ; Pennington & Chen, ; Qin et al, ; Sumy et al, ).…”

“…In this study, we analyze the source process of a Mw 4.0 earthquake that occurred on 8 April 2015, the largest event in a well‐recorded sequence near Guthrie in central Oklahoma (Chen et al, ). We apply the empirical Green's function (EGF) technique in both time and frequency domains to obtain an unusually detailed look at the rupture complexity of this moderate event.…”

Multiscale Analysis of Spatiotemporal Relationship Between Injection and Seismicity in Oklahoma

“…While the large‐scale spatial expansion from areas with high‐rate injection is clear for some cases, individual sequences often exhibit different migration directions, for example, the Woodward sequence in western Oklahoma appears to migrate in the opposite direction relative to the large‐scale pattern (Goebel et al, ). It is likely that such far‐field triggering is indicative of rapid lateral fluid transport from the area of high‐rate injection, while individual sequence spatial migration may not necessarily follow the large‐scale pattern but are reflecting the hydraulic properties and stress transfer along seismogenic faults within the crystalline basement (Chen et al, ). Understanding these differences in observations would require systematic multiscale analyses that consider both large and small scales.…”