Laboratory Earthquakes from the Cornell 3 m apparatus

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https://hdl.handle.net/1813/66670

This data was recorded from a suite of laboratory experiments described in an ongoing set of publications starting with Ke, et al., 2018, Geophysical Research Letters. https://doi.org/10.1029/2018GL080492.

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Data from: Seismicity Migration from Fluid Injection: Laboratory Experiments and Numerical Models Illuminate Volume-Driven versus Pressure-Diffusion-Driven Migrations
Song, Jun Young; Liu, Lingfu; Arson, Chloé; McLaskey, Gregory C. (2025-12-23)
These files contain data supporting all results reported in Song et al. We found: Fluid injection into the subsurface can induce seismicity by reactivating shear rupture, which typically produces larger earthquake magnitudes than tensile rupture. In laboratory shear rupture experiments, pressurization of the entire fault is often limited because large unconfined samples allow fluid to leak at free surfaces. In this study, we investigated shear fault reactivation by directly injecting fluid into a PMMA fault (760 mm long, 76 mm high) formed as the interface between two separate PMMA blocks. To prevent leakage in the 76 mm dimension, we made a low permeability barrier by coating the outer edges of the fault with Teflon tape. Fluid pressure then extended along the 760 mm dimension, resulting in the migration of seismicity away from the injection well. Changes in injection rate and fluid viscosity revealed two mechanisms: (1) slow injection rate or low-viscosity fluid caused seismicity migration governed by pressure diffusion, and (2) fast injection rate or high-viscosity fluid caused seismicity migration proportional to injected volume. Simulations with a 2D poroelastic model showed that seismicity migrated with the fluid pressure front in the volume-driven regime, whereas fluid pressure advanced well ahead of seismicity in the pressurediffusion-driven regime. These results highlight that Teflon tape effectively sealed faults and controlled fluid flow, and that injection rate and fluid viscosity have a strong impact on fault slip and induced seismicity.
Data from: Fully Contained Laboratory Earthquakes: The Effect of Asperity Aspect Ratio and Free Surfaces
Cebry, Sara Beth L.; Song, Jun Young; McLaskey, Gregory C. (2025-12-23)
These files contain data supporting all results reported in Cebry et al. We found: Corner frequency (fc) and seismic moment (M0) are key parameters derived from seismic signals that are used to characterize earthquake stress drop, rupture area, and slip. These parameters are also affected by fault geometry and boundary conditions. However, the systematic study of these effects in laboratory settings has been challenging. This study presents laboratory earthquake experiments that examine how rupture dynamics are influenced by (1) the aspect ratio of rectangular PMMA velocity-weakening (VW) asperities surrounded by the Teflon velocity-strengthening (VS) patches, and (2) whether the sides of a VW asperity are confined with VS patches or are free surfaces. We found that increasing confinement by reducing free surfaces or increasing the VW asperity aspect ratio stabilizes fault slip, so that higher normal stress is required to transition from aseismic to seismic slip. Increased confinement and high aspect ratios also reduced M0 and increased fc, both of which were determined from the radiated seismic waves. M0 and fc were primarily controlled by the shorter dimension of the VW asperity. Analysis of high-frequency acoustic emission signals revealed that ruptures on high-aspect-ratio VW asperities propagated more unidirectionally, whereas ruptures on square VW asperities were more complex. Further, the high-aspect-ratio asperities were more likely to be eroded by surrounding VS regions while lowaspect-ratio asperities were more likely to rupture into the VS surroundings. These results demonstrate that both the confinement from surrounding stable areas and the geometry of the seismogenic patch can affect rupture nucleation, propagation, and seismic source characteristics.
Scripts from: Nonlocal dissipation far from the rupture tip affects both rupture dynamics and arrest
Basu, Dibya Jyoti; Ke, Chun-Yu; Kammer, David S.; McLaskey, Gregory C. (2025-09)
These files are from the numerical simulations conducted in Basu et al., "Nonlocal dissipation far from the rupture tip affects both rupture dynamics and arrest" We found: Linear elastic fracture mechanics is useful for understanding earthquake rupture, but seismological evidence suggests earthquake fracture energy spanning from 1 J/m2 to 10 MJ/m2. Fracture energy is localized to the rupture tip, so high seismological estimates should instead be considered breakdown work Wb, which includes nonlocal energy dissipation, possibly arising from long-tailed secondary weakening (LTSW) that scales with final slip. However, it is unclear if LTSW and associated large Wb causes earthquakes to rupture faster and grow larger or propagate more slowly and arrest easily. We report numerical models of dynamic rupture that illuminate effects of LTSW on rupture propagation and arrest due to heterogeneous initial stress. Our findings indicate that secondary weakening always leads to a higher rupture speed and a larger rupture extent compared to scenarios without it. Additional stress drop associated with secondary weakening does more to “fuel” rupture than larger Wb does to arrest rupture.
Data from: Fault healing and asperity partitioning on a frictionally heterogeneous laboratory fault
Song, Jun Young; Cattania, Camilla; McLaskey, Gregory (2025-06-04)
These data are from Laboratory Earthquake Experiments from the Cornell 0.76 m apparatus in support of the following research: Natural faults likely include both Velocity-Weakening (VW) and Velocity-Strengthening (VS) sections. We developed a laboratory method to replicate this frictional heterogeneity using a 760 mm long Polymethyl methacrylate (PMMA) block with eleven VW patches (bare PMMA) separated by VS barriers (Teflon tape). We compared the behavior of this Multiple Patches (MP) arrangement to those from One single VW Patch (OP) with the same total VW fault area. Seismic events that occurred in clusters with foreshocks and aftershocks were observed only in the MP tests, and total slip, maximum slip rate, seismic moment, and recurrence time of the largest event (termed the mainshock) in a slip cycle, were an order of magnitude smaller in the MP tests compared to the OP tests. Varying the loading rates, we found that the mainshock magnitude in the OP tests increased with recurrence time as expected due to fault healing. In contrast, the mainshock magnitude in the MP tests decreased with increasing recurrence time due to the increased effectiveness of VS barriers at slower loading rates. In some MP tests, foreshock-like events migrated at ~0.7 m/s, followed by faster reverse migration at ~7 m/s, resembling Rapid Tremor Reversal (RTR) in subduction zones. We used a numerical simulation to quantitatively reproduce the RTR-like behavior, help explain its mechanics, and constrain the friction properties of the laboratory system. Overall, our findings highlight how identical structural features on heterogeneous faults can behave differently under different loading conditions due to the velocity dependence of VS barriers.
Data from: Heterogeneous high frequency seismic radiation from complex ruptures
Cebry, Sarah Beth L.; McLaskey, Gregory C. (2024-04-11)
These data are from Laboratory Earthquake Experiments from the Cornell 0.76 m apparatus in support of the following research: To investigate the effect of a normal stress heterogeneity on radiated spectra, we utilized a PMMA laboratory fault with a single, localized bump. By varying the bump prominence (defined here as normal stress on the bump divided by average normal stress across the entire fault), we produced earthquake-like ruptures that ranged from smooth, continuous ruptures to complex ruptures with variable rupture propagation velocity, slip distribution, and stress drop. High prominence bumps produced complex events that radiated more high frequency energy, relative to low frequency energy, than continuous events without a bump. In complex ruptures, the high frequency energy showed significant spatial variation correlated with peak slip rate and maximum local stress drop. Continuous ruptures emitted spatially uniform bursts of high frequency energy. Near-field peak ground acceleration (PGA) measurements of complex ruptures show nearly an order-of-magnitude higher PGA near the bump than elsewhere. We propose that for natural faults, geometric heterogeneities may be a plausible explanation for commonly observed order-of-magnitude variations in near-fault PGA.
Data from: Laboratory earthquake ruptures contained by velocity strengthening fault patches
Song, Jun Young; McLaskey, Gregory C. (2024)
These data are from Laboratory Earthquake Experiments from the Cornell 0.76 m apparatus in support of the following research: To better understand how normal stress heterogeneity affects earthquake rupture, we conducted laboratory experiments on a 760 mm PMMA sample with a 25 mm “bump” of locally higher normal stress. We systematically varied the sample-average normal stress and bump prominence. For bumps with low prominence (bump normal stress over sample average normal stress < 6) the rupture simply propagated through the bump and produced regular sequences of periodic stick-slip events. Bumps with higher prominence (>6) produced complex rupture sequences with variable timing and ruptures sizes, and this complexity persisted for multiple stick-slip supercycles. During some events the bump remained locked and acted as a barrier that completely stopped rupture. In other events, a dynamic rupture front terminated at the locked bump, but rupture reinitiated on the other side of the bump after a brief pause of 0.3-1 ms. Only when stress on the bump was near critical did the bump slip and unload built up strain energy in one large event. Thus, a sufficiently prominent bump acted as a barrier (energy sink) when it was far from critically stressed and as an asperity (energy source) when it was near critically stressed. Similar to an earthquake gate, the bump never acted as a permanent barrier. In the experiments, we resolve the above rupture interactions with a bump as separate rupture phases; however, when observed through the lens of seismology, it may appear as one continuous rupture that speeds up and slows down. The complicated rupture-bump interactions also produced enhanced high frequency seismic waves recorded with piezoelectric sensors.
Data from: Earthquake rupture interactions with a high normal stress bump
Cebry, Sara B. L.; Sorhaindo, Kian; McLaskey, Gergory C. (2023-06-21)
These files contain data supporting all results reported in Cebry et al. Earthquake rupture interactions with a high normal stress bump. In Cebry et al. we found: To better understand how normal stress heterogeneity affects earthquake rupture, we conducted laboratory experiments on a 760 mm PMMA sample with a 25 mm “bump” of locally higher normal stress. We systematically varied the sample-average normal stress and bump prominence. For bumps with low prominence (bump normal stress over sample average normal stress < 6) the rupture simply propagated through the bump and produced regular sequences of periodic stick-slip events. Bumps with higher prominence (>6) produced complex rupture sequences with variable timing and ruptures sizes, and this complexity persisted for multiple stick-slip supercycles. During some events the bump remained locked and acted as a barrier that completely stopped rupture. In other events, a dynamic rupture front terminated at the locked bump, but rupture reinitiated on the other side of the bump after a brief pause of 0.3-1 ms. Only when stress on the bump was near critical did the bump slip and unload built up strain energy in one large event. Thus, a sufficiently prominent bump acted as a barrier (energy sink) when it was far from critically stressed and as an asperity (energy source) when it was near critically stressed. Similar to an earthquake gate, the bump never acted as a permanent barrier. In the experiments, we resolve the above rupture interactions with a bump as separate rupture phases; however, when observed through the lens of seismology, it may appear as one continuous rupture that speeds up and slows down. The complicated rupture-bump interactions also produced enhanced high frequency seismic waves recorded with piezoelectric sensors.
Data from: Creep fronts and complexity in laboratory earthquake sequences illuminate delayed earthquake triggering
Cebry, Sara Beth L.; Ke, Chun-Yu; Shreedharan, Srisharan; Marone, Chris; Kammer, David S.; McLaskey, Gregory C. (2022-09-14)
These data are from Laboratory Earthquake Experiments from the Cornell 0.76 m apparatus in support of the following research: Earthquakes occur in clusters or sequences that arise from complex triggering mechanisms, but direct measurement of the slow subsurface slip responsible for delayed triggering is rarely possible. We investigate the origins of complexity and its relationship to heterogeneity using an experimental fault with two dominant seismic asperities. The fault is composed of quartz powder, a material common to natural faults, sandwiched between 760 mm long polymer blocks that deform the way 10 meters of rock would behave. We observe periodic repeating earthquakes that transition into aperiodic and complex sequences of fast and slow events. Neighboring earthquakes communicate via migrating slow slip, which resembles creep fronts observed in numerical simulations and on tectonic faults. Utilizing both local stress measurements and numerical simulations, we observe that the speed and strength of creep fronts are highly sensitive to fault stress levels left behind by previous earthquakes, and may serve as on-fault stress meters.
Data from: The Role of Background Stress State in Fluid-Induced Aseismic Slip and Dynamic Rupture on a 3-meter Laboratory Fault
Cebry, Sara B. L.; Ke, Chun-Yu; McLaskey, Gregory C. (2022-05)
These files contain data supporting all results reported in: "The Role of Background Stress State in Fluid-Induced Aseismic Slip and Dynamic Rupture on a 3-meter Laboratory Fault" by Cebry et al., where we found: Fluid injection stimulates seismicity far from active tectonic regions, however the details of how fluids modify on-fault stresses and initiate seismic events remains poorly understood. We conducted laboratory experiments using a biaxial loading apparatus with a 3 m saw-cut granite fault and compared events induced at different background shear stress levels. Water was injected at 10 ml/min and normal stress was constant at 4 MPa. In all experiments, aseismic slip initiated on the fault near the location of fluid injection and dynamic rupture eventually initiated from within the aseismic slipping patch. When the fault was near critically stressed, seismic slip initiated only seconds after MP a-level injection pressures were reached and the dynamic rupture propagated beyond the fluid pressure perturbed region. At lower stress levels, dynamic rupture initiated hundreds of seconds later and was limited to regions where aseismic slip had significantly redistributed stress from within the pressurized region to neighboring locked patches. We find that slow slip initiated when local stresses exceeded Coulomb failure criteria, but initiation of dynamic rupture required additional criteria to be met. Even high background stress levels required aseismic slip to modify on-fault stress to meet initiation criteria. We also observed slow slip events prior to dynamic rupture. Overall, our experiments suggest that initial fault stress, relative to fault strength, is a critical factor in determining whether a fluid-induced rupture will "runaway" or whether a fluid induced rupture will remain localized to the fluid pressurized region.
Data from: Seismic swarms produced by rapid fluid injection into a low permeability laboratory fault
Cebry, Sara Beth L.; McLaskey, Gregory C. (2020-12-18)
These data are from Laboratory Earthquake Experiments from the Cornell 0.76 m apparatus in support of the following research: Fluid injection, from activities such wastewater disposal, hydraulic stimulation, or enhanced geothermal systems, decreases effective normal stress on faults and promotes slip. Nucleation models suggest the slip at low effective normal stress will be stable and aseismic—contrary to observed increases in seismicity that are often attributed to fluid injection. We conducted laboratory experiments using a biaxial loading apparatus that demonstrate how an increase in fluid pressure can induce “stick-slip” events along a preexisting saw-cut fault in a poly(methyl methacrylate) (PMMA) sample. We compared slip events generated by externally squeezing the sample (shear-triggered) to those due to direct fluid injection (fluid-triggered) and studied the effects of injection rate and stress levels. Shear-triggered slip events began on a localized nucleation patch and slip smoothly accelerated from slow and aseismic to fast and seismic. Fluid-triggered slip events initiated far more abruptly and were associated with swarms of tiny foreshocks. These foreshocks were able to bypass the nucleation process and jump-start a mainshock resulting in an abrupt initiation. Analysis of these foreshocks indicates that the injection of fluid into a low permeability fault promotes heterogeneous stress and strength which can cause many events to initiate—some of which grow large. We conclude that while a reduction in effective normal stress stabilizes fault slip, rapid fluid injection into a low permeability fault increases multi-scale stress/strength heterogeneities which can initiate small seismic events that have the potential to rapidly grow, even into low stress regions.

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