Competition between slow slip and damage on and off faults revealed in 4D synchrotron imaging experiments

Renard, François; McBeck, Jessica; Cordonnier, B.

doi:10.1016/j.tecto.2020.228437

Cited by 8 publications

(6 citation statements)

References 43 publications

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“…Samples were saw‐cut with an orientation of 30° to the vertical axis, creating an artificial fault plane. The fault roughness was imposed by hand using #240 grit sandpaper, generating a smooth fault, optimally oriented for reactivation, avoiding the propagation of new secondary fractures in the surrounding medium (Renard et al., 2020 ). The lack of secondary fracture formation under this configuration has been verified in previous experimental work (e.g., Acosta et al.…”

Section: Experimental Methodsmentioning

confidence: 99%

Origin of the Co‐Seismic Variations of Elastic Properties in the Crust: Insight From the Laboratory

Paglialunga

Passelègue

Acosta

et al. 2021

Geophysical Research Letters

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Seismological observations highlighted that earthquakes are often followed by changes in elastic properties around the fault zone. Here, we studied the origin of these variations using stick‐slip experiments on saw‐cut granite samples presenting different degrees of bulk damage (i.e., microcracks). Stick‐slip events were induced under triaxial compression configuration with continuous active ultrasonic measurements at confining pressures representative of upper crustal conditions (15–120 MPa). Both the P‐wave velocity (VnormalP) and amplitude (AnormalP) showed drops, concurrently with stress drops, and had a non‐monotonic dependence toward the fault's stress state. Our experimental results suggest that co‐seismic changes in VnormalP were mostly controlled by the elastic re‐opening of microcracks in the bulk, rather than by co‐seismic damage or the formation of fault gouge. Co‐seismic changes in AnormalP were controlled by a combination of elastic re‐opening of microcracks in the bulk and inelastic processes (i.e., co‐seismic damage and gouge formation and dilation).

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Section: Experimental Methodsmentioning

confidence: 99%

Origin of the Co‐Seismic Variations of Elastic Properties in the Crust: Insight From the Laboratory

Paglialunga

Passelègue

Acosta

et al. 2021

Geophysical Research Letters

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“…This observation indicates that the fault network locked at the end of the creep burst, and volumetric strain concentrated below this fault network, producing a lower creep rate. In a series of XCT experiments on granite saw‐cut samples where the initial fault surface roughness was varied, our group has observed that rougher faults could lock and produce off‐fault damage (Renard et al, 2020). The interpretation was that asperities along a fault surface with a larger roughness amplitude would lock, allowing larger stress concentrations to propagate in the off‐fault volume and creating damage there.…”

Section: Discussionmentioning

confidence: 99%

Creep Burst Coincident With Faulting in Marble Observed in 4‐D Synchrotron X‐Ray Imaging Triaxial Compression Experiments

et al. 2020

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Faults in carbonate rocks show both seismic and aseismic deformation processes, leading to a wide range of slip velocities. We deformed two centimeter-scale cores of Carrara marble at 25°C and imaged the nucleation and growth of faults using dynamic synchrotron X-ray microtomography. The first sample experienced a constant confinement of 30 MPa and no pore fluid. The second sample experienced confinement in the range 35-23 MPa and water as a pore fluid at 10 MPa pore pressure. We increased the axial stress by steps until creep deformation occurred and imaged deformation in 4-D. The samples deformed with a quasi-constant or increasing strain rate when the differential stress was constant, a process called creep. However, for both samples, we also observed transient events that include the acceleration of creep, that is, creep bursts, phenomena similar to slow slip events that occur in continental active faults. During these transient creep events, strain rates increase and correlate in time with strain localization and the slow development of system-spanning fault networks. In both samples, the acceleration of opening and shearing of microfractures accommodated creep bursts. High-resolution time-lapse X-ray microtomography imaging and digital image correlation during triaxial deformation quantify creep in laboratory faults at subgrain spatial resolution. This work demonstrates that transient creep events, that is, creep bursts or slow slip events, correlate with the nucleation and slow growth of faults and not only with slip on preexisting faults. Plain Language Summary Active faults may slip at velocities close to 1 m/s during earthquakes and may also slip at much slower rates, in creep. Sometimes such creep is continuous in time; sometimes it is transient and occurs as creep bursts, also called slow slip events. Using state-of-the-art synchrotron X-ray imaging of core samples of Carrara marble deformed under constant stress conditions and room temperature, we identified such creep bursts. Our 4-D imaging technique allows seeing through the sample and characterizing the microphysical processes that produce creep bursts. Results show that the acceleration of microfractures nucleation, growth, and coalescence in the sample may lead to the formation of system-spanning faults that coincide in time with the macroscopically observed creep burst. These results demonstrate that creep bursts may not only correspond to slow slip events on active preexisting faults but may also indicate the slow development of new active faults.

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“…On the other hand, slow rupture speed, high aftershock productivity (Liu et al, 2019), and very complex fault geometry (Wang & Zhan, 2020) all indicate an immature fault system, implying rougher and stronger faults in comparison with the neighboring plate boundary type fault (SAF). Recent rock experiments also show that conjugate fault ruptures tend to occur in rock samples with rougher fault friction (Renard et al, 2020). In addition, near-fault plastic deformation and encountering of rupture barriers (Xu & Ben-Zion, 2013) were invoked…”

Section: Geophysical Research Lettersmentioning

confidence: 99%

Highly Heterogeneous Pore Fluid Pressure Enabled Rupture of Orthogonal Faults During the 2019 Ridgecrest Mw7.0 Earthquake

Shi¹,

Wei²

2021

Preprint

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Here, we show that the 2019 Mw7.0 Ridgecrest mainshock as well as its Mw6.5 foreshock ruptured orthogonal conjugate faults. We invert the waveforms recorded by the dense strong motion network at relatively high frequencies (up to 1&#160;Hz for&#160;P; 0.25&#160;Hz for&#160;S) to derive multiple&#8208;point source models for both events, aided by path calibrations from a Mw5.4 and a Mw5.5 earthquake. We demonstrate that the mainshock started from a shallow (3&#160;km) depth with a Mw5.2 event and ruptured the main fault branches oriented in the NW&#8208;SE direction. At ~11&#160;s, two Mw6.2 subevents took place on the SW&#8208;NE oriented fault branches that conjugate to the main fault to the NE and SW. The SW branch rupture partially overlapped with the foreshock rupture. We suggest the coseismic rupture on nearly orthogonal faults was enabled by high pore fluid pressure, which greatly weakened the immature fault system in a heterogeneous way.

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Competition between slow slip and damage on and off faults revealed in 4D synchrotron imaging experiments

Cited by 8 publications

References 43 publications

Origin of the Co‐Seismic Variations of Elastic Properties in the Crust: Insight From the Laboratory

Origin of the Co‐Seismic Variations of Elastic Properties in the Crust: Insight From the Laboratory

Creep Burst Coincident With Faulting in Marble Observed in 4‐D Synchrotron X‐Ray Imaging Triaxial Compression Experiments

Highly Heterogeneous Pore Fluid Pressure Enabled Rupture of Orthogonal Faults During the 2019 Ridgecrest Mw7.0 Earthquake

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