A Systematic Assessment of the Spatiotemporal Evolution of Fault Activation Through Induced Seismicity in Oklahoma and Southern Kansas

Abstract

Much of Oklahoma and southern Kansas has seen widespread seismic activity in the last decade that is attributed to large‐scale wastewater disposal into the Arbuckle group. Using a waveform‐relocated earthquake catalog, we perform a systematic study of the activity on several hundreds of identified faults. We use 93 sequences with at least 30 events for a detailed analysis of their spatiotemporal evolution. For most awakened faults, seismicity tends to initiate at shallower depth and migrates deeper along the faults as the sequence proceeds. No major sequence starts with the largest earthquake, and many sequences initiate months before they rise to peak activity. We study temporal clustering as a means to quantify earthquake interactions. Some sequences show no temporal clustering similar to Poissonian background seismicity but at much higher rate than the natural background. Other sequences exhibit strong temporal clustering akin to main shock‐aftershock sequences. We conclude that once initiated by anthropogenic forcing, portions of the activated faults in the Oklahoma/Kansas area are close enough to failure to continue failing through earthquake interactions. In many sequences, including those with the largest earthquakes, seismicity continues within the previously activated region rather than by growing the activated area. Therefore, monitoring seismicity with a low magnitude threshold and high location precision has the potential to detect minor activity as it initiates failure on specific faults and thus provide time to take actions to mitigate the occurrence of potentially damaging earthquakes.

How faults wake up: The Guthrie-Langston, Oklahoma earthquakes

“…A delay from initiation to the highest rate of activity is observed in many sequences throughout Oklahoma (Schoenball and Ellsworth, 2017a). Preshock activity typically builds over the course of a sequence, but sequences never start with the largest event.…”

“…Furthermore, we notice that the trends of mapped fault structures differ from the trends that are apparent from the earthquake locations. To further study the network of faults, we applied the DBSCAN algorithm (Ester et al, 1996) to objectively identify individual faults in the basement (Schoenball and Ellsworth, 2017a). For each fault, we measure strike and dip using principal component analysis.…”

Hydromechanical Earthquake Nucleation Model Forecasts Onset, Peak, and Falling Rates of Induced Seismicity in Oklahoma and Kansas

“…It may be possible to tune the model parameters in the Gardner and Knopoff (1974) and Reasenberg (1985) methods to recent earthquake catalogs in the study area. Alternatively, in their study of fault activation and earthquake interactions, Schoenball and Ellsworth (2017b) provide insight into novel declustering methods that may be applicable in areas of induced seismicity. Finally, it would be possible to integrate the hydromechanical model as the background rate within an epidemic-type aftershock framework to more appropriately evaluate frequency-magnitude statistics and the impact of large earthquakes (Llenos & Michael, 2013).…”

Accelerated Fill‐Up of the Arbuckle Group Aquifer and Links to U.S. Midcontinent Seismicity

“…Earthquake activity has recently increased in central Kansas, since March 2018, with three M 3+ earthquakes occurring near the city of Hutchinson, in Reno County (USGS, ). Seismicity in these counties has occurred almost exclusively in the Precambrian crystalline basement, below the Arbuckle (Rubinstein et al, ; Schoenball & Ellsworth, ), suggesting that the aquifer is hydraulically connected to the deeper basement, where faults are in critical equilibrium and can slip under small stress changes (0.01–0.1 MPa; Reasenberg & Simpson, ; Stein, ). Pore pressure increases and pressure diffusion are considered the first‐order driving mechanism for unclamping these faults and triggering fault slip (Shapiro, ; Shapiro et al, ; Segall & Lu, ); however, pressure data for the Arbuckle are surprisingly limited, especially given the large number of wells that inject into the zone (Bidgoli et al, ; Kroll et al, ; Nolte et al, ; Schwab et al, ).…”