Geology topics

Kayla A. Kroll

Publications and source records attributed to Kayla A. Kroll.

5 recordsLinked to original sources

USGS2024

Cyclic injection leads to larger and more frequent induced earthquakes under volume-controlled conditions

As carbon storage technologies advance globally, methods to understand and mitigate induced earthquakes become increasingly important. Although the physical processes that relate increased subsurface pore pressure changes to induced earthquakes have long been known, reliable methods to forecast and control induced seismic sequences remain elusive. Suggested reservoir engineering scenarios for mitigating induced earthquakes typically involve modulation of the injection rate. Some operators have implemented periodic shutdowns (i.e., effective cycling of injection rates) to allow reservoir pressures to equilibrate (e.g., Paradox Valley) or shut‐in wells after the occurrence of an event of concern (e.g., Basel, Switzerland). Other proposed scenarios include altering injection rates, actively managing pressures through coproduction of fluids, and preinjection brine extraction. In this work, we use 3D physics‐based earthquake simulations to understand the effects of different injection scenarios on induced earthquake rates, maximum event magnitudes, and postinjection seismicity. For comparability, the modeled injection considers the same cumulative volume over the project’s operational life but varies the schedule and rates of fluid injected. Simulation results show that cyclic injection leads to more frequent and larger events than constant injection. Furthermore, with intermittent injection scenario, a significant number of events are shown to occur during pauses in injection, and the seismicity rate remains elevated for longer into the postinjection phase compared to the constant injection scenario.

Seismological Research Letters↗

USGS2021

Characterizing stress orientations in southern Kansas

Induced seismicity predominantly occurs along faults that are optimally oriented to the local principal compressive stress direction, and the characterization of these stress orientations is an important component of understanding seismic hazards. The seismicity rate in southern Kansas rapidly increased in 2013 primarily due to the disposal of large volumes of wastewater into the Arbuckle Group. Previously, local stress orientations in this area were poorly constrained, which limited our understanding of the complex faulting and diverse earthquake mechanisms in this region. We use shear‐wave splitting and focal mechanism inversion techniques to create multiple, independent estimates of maximum horizontal stress directions ( ⁠ S H max ">

Kansas↗

USGS2017

Delayed seismicity rate changes controlled by static stress transfer

On 15 June 2010, a M w 5.7 earthquake occurred near Ocotillo, California, in the Yuha Desert. This event was the largest aftershock of the 4 April 2010 M w 7.2 El Mayor-Cucapah (EMC) earthquake in this region. The EMC mainshock and subsequent Ocotillo aftershock provide an opportunity to test the Coulomb failure hypothesis (CFS). We explore the spatiotemporal correlation between seismicity rate changes and regions of positive and negative CFS change imparted by the Ocotillo event. Based on simple CFS calculations we divide the Yuha Desert into three subregions, one triggering zone and two stress shadow zones. We find the nominal triggering zone displays immediate triggering, one stress shadowed region experiences immediate quiescence, and the other nominal stress shadow undergoes an immediate rate increase followed by a delayed shutdown. We quantitatively model the spatiotemporal variation of earthquake rates by combining calculations of CFS change with the rate-state earthquake rate formulation of Dieterich (1994), assuming that each subregion contains a mixture of nucleation sources that experienced a CFS change of differing signs. Our modeling reproduces the observations, including the observed delay in the stress shadow effect in the third region following the Ocotillo aftershock. The delayed shadow effect occurs because of intrinsic differences in the amplitude of the rate response to positive and negative stress changes and the time constants for return to background rates for the two populations. We find that rate-state models of time-dependent earthquake rates are in good agreement with the observed rates and thus explain the complex spatiotemporal patterns of seismicity.

California↗

USGS2017

Poroelastic properties of the Arbuckle Group in Oklahoma derived from well fluid level response to the 3 September 2016 M w 5.8 Pawnee and 7 November 2016 M w 5.0 Cushing earthquakes

The Arbuckle Group (Arbuckle) is a basal sedimentary unit that is the primary target for saltwater disposal in Oklahoma. Thus, the reservoir characteristics of the Arbuckle, including how the poroelastic properties change laterally and over time are of significant interest. We report observations of fluid level changes in two monitoring wells in response to the 3 September 2016 M w 5.8 Pawnee and the 7 November 2016 M w 5.0 Cushing earthquakes. We investigate the relationship between static strain resulting from these events and the fluid level changes observed in the wells. We model the fluid level response by estimating static strains from a set of earthquake source parameters and spatiotemporal poroelastic properties of the Arbuckle in the neighborhood of the monitoring wells. Results suggest that both the direction of the observed fluid level step and the amplitude can be predicted from the computed volumetric strain change and a reasonable set of poroelastic parameters. Modeling results indicate that poroelastic parameters differ at the time of the Pawnee and Cushing earthquakes, with a moderately higher Skempton’s coefficient required to fit the response to the Cushing earthquake. This may indicate that dynamic shaking resulted in physical alteration of the Arbuckle at distances up to ∼50 km from the Pawnee earthquake.

Oklahoma↗

USGS2015

Stress- and structure-controlled anisotropy in a region of complex faulting—Yuha Desert, California

We examine shear velocity anisotropy in the Yuha Desert, California using aftershocks of the 2010 M7.2 El Mayor-Cucapah earthquake. The Yuha Desert is underlain by a complex network of right- and left-lateral conjugate faults, some of which experienced triggered slip during the El Mayor-Cucapah earthquake. An automated method that implements multiple measurement windows and a range of bandpass filters is used to estimate the fast direction ( ϕ ) and delay time ( δt ) of the split shear waves. We find an average ϕ oriented approximately north–south suggesting it is primarily controlled by the regional maximum compressive stress direction. However, the spatial variability in ϕ reveals that the fault structures that underlie the Yuha Desert also influence the measured splitting parameters. We infer that the northeast- and northwest-oriented ϕ reflect shear fabric subparallel to the conjugate fault structures. We do not observe a simple correlation between δt and hypocentral distance. Instead, the observed spatial variation in δt suggests that near-source variation in anisotropic strength may be equal to or more important than effects local to the station. No temporal variation in splitting parameters is observed during the 70-day period following the main shock. In this region of complex faulting, we observe a spatially variable pattern of anisotropy that is both stress- and structure-controlled. This study suggests that shear fabric can form even along short, discontinuous fault strands with minimal offset.

California↗