Chun-Yu Ke

Publication: Earthquake energy dissipation in a fracture mechanics framework

2024-06-18T00:00:00+08:00

Authors: David S. Kammer, Gregory C. McLaskey, Rachel E. Abercrombie, Jean-Paul Ampuero, Camilla Cattania, Massimo Cocco, Luca Dal Zilio, Georg Dresen, Alice-Agnes Gabriel, Chun-Yu Ke, Chris Marone, Paul Antony Selvadurai, Elisa Tinti

Earthquakes are rupture-like processes that propagate along tectonic faults and cause seismic waves. The propagation speed and final area of the rupture, which determine an earthquake’s potential impact, are directly related to the nature and quantity of the energy dissipation involved in the rupture process. Here, we present the challenges associated with defining and measuring the energy dissipation in laboratory and natural earthquakes across many scales. We discuss the importance and implications of distinguishing between energy dissipation that occurs close to and far behind the rupture tip, and we identify open scientific questions related to a consistent modeling framework for earthquake physics that extends beyond classical Linear Elastic Fracture Mechanics.

Kammer, D. S., McLaskey, G. C., Abercrombie, R. E., Ampuero, J.-P., Cattania, A., Cocco, M., Dal Zillo, L., Dresen, G., G., Gabriel, A.-A., Ke, C.-Y,, Marone, C., Selvadurai, P. A., Tinti, E. (2024) Earthquake energy dissipation in a fracture mechanics framework. Nature Communications, 15, 4736. doi: 10.1038/s41467-024-47970-6.

Publication: The influence of AGEs and enzymatic cross-links on the mechanical properties of collagen fibrils

2023-04-29T00:00:00+08:00

Authors: Julia Kamml, Chun-Yu Ke, Claire Acevedo, David S. Kammer

Collagen, one of the main building blocks for various tissues, derives its mechanical properties directly from its structure of cross-linked tropocollagen molecules. The cross-links are considered to be a key component of collagen fibrils as they can change the fibrillar behavior in various ways. For instance, enzymatic cross-links (ECLs), one particular type of cross-links, are known for stabilizing the structure of the fibril and improving material properties, while cross-linking AGEs (Advanced-Glycation Endproducts) have been shown to accumulate and impair the mechanical properties of collageneous tissues. However, the reasons for whether and how a given type of cross-link improves or impairs the material properties remain unknown, and the exact relationship between the cross-link properties and density, and the fibrillar behavior is still not well understood. Here, we use coarse-grained steered molecular models to evaluate the effect of AGEs and ECLs cross-links content on the deformation and failure properties of collagen fibrils. Our simulations show that the collagen fibrils stiffen at high strain levels when the AGEs content exceeds a critical value. In addition, the strength of the fibril increases with AGEs accumulation. By analyzing the forces within the different types of cross-links (AGEs and ECLs) as well as their failure, we demonstrate that a change of deformation mechanism is at the origin of these observations. A high AGEs content reinforces force transfer through AGEs cross-links rather than through friction between sliding tropocollagen molecules, which leads to failure by breaking of bonds within the tropocollagen molecules. We show that this failure mechanism, which is associated with lower energy dissipation, results in more abrupt failure of the collagen fibril. Our results provide a direct and causal link between increased AGEs content, inhibited intra-fibrillar sliding, increased stiffness, and abrupt fibril fracture. Therefore, they explain the mechanical origin of bone brittleness as commonly observed in elderly and diabetic populations. Our findings contribute to a better understanding of the mechanisms underlying impaired tissue behavior due to elevated AGEs content and could enable targeted measures regarding the reduction of specific collagen cross-linking levels.

Kamml, J., Ke, C.-Y., Acevedo, C. & Kammer, D. S. (2023) The Influence of AGEs and Enzymatic Cross-Links on the Mechanical Properties of Collagen Fibrils. Journal of the Mechanical Behavior of Biomedical Materials, 143, 105870. doi: 10.1016/j.jmbbm.2023.105870.

Featured in Cornell Chronicle

2022-12-01T00:00:00+08:00

Our latest paper is featured in Cornell Chronicle.

Cebry, S. B. L.*, Ke, C.-Y.*, Shreedharan, S., Marone, C., Kammer, D. S. & McLaskey, G. C. (2022) Creep fronts and complexity in laboratory earthquake sequences illuminate delayed earthquake triggering. Nature Communications, 13:6839. doi: 10.1038/s41467-022-34397-0. *co-first authors

The Cornell Chronicle, Cornell’s source of official news since 1969, is part of University Relations. The site publishes daily news about research, outreach, events and the Cornell community.

Featured in Nature Communications

2022-11-13T00:00:00+08:00

Our latest paper is featured in Nature Communications Editors’ Highlights - Earth science.

Cebry, S. B. L.*, Ke, C.-Y.*, Shreedharan, S., Marone, C., Kammer, D. S. & McLaskey, G. C. (2022) Creep fronts and complexity in laboratory earthquake sequences illuminate delayed earthquake triggering. Nature Communications, 13:6839. doi: 10.1038/s41467-022-34397-0. *co-first authors

The Editors’ Highlights pages aim to showcase the 50 best papers recently published in an area, and we routinely replace papers as more great research is published at Nature Communications.

Publication: Creep fronts and complexity in laboratory earthquake sequences illuminate delayed earthquake triggering

2022-11-12T00:00:00+08:00

Authors: Sara Beth L. Cebry*, Chun-Yu Ke*, Srisharan Shreedharan, Chris Marone, David S. Kammer, Gregory C. McLaskey
*co-first authors

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.

Cebry, S. B. L.*, Ke, C.-Y.*, Shreedharan, S., Marone, C., Kammer, D. S. & McLaskey, G. C. (2022) Creep fronts and complexity in laboratory earthquake sequences illuminate delayed earthquake triggering. Nature Communications, 13:6839. doi: 10.1038/s41467-022-34397-0. *co-first authors

Featured in Yale Scientific Magazine

2022-09-04T00:00:00+08:00

Our recent work is featured in Yale Scientific Magazine.

Ke, C.-Y., McLaskey, G. C. & Kammer, D. S. (2022) Earthquake breakdown energy scaling despite constant fracture energy. Nature Communications, 13, 1005. doi: 10.1038/s41467-022-28647-4

The Yale Scientific Magazine, established in 1894, is the nation’s oldest college science publication and the premier science publication at Yale.

Publication: The Role of Background Stress State in Fluid-Induced Aseismic Slip and Dynamic Rupture on a 3-m Laboratory Fault

2022-08-17T00:00:00+08:00

Authors: Sara Beth Leach Cebry, Chun-Yu Ke, Gregory C. McLaskey

Fluid injection stimulates seismicity far from active tectonic regions. However, the details of how fluids modify on-fault stresses and initiate seismic events remain 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 levels of background shear stress. 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 MPa-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 found that the initiation of slow slip was broadly consistent with a Coulomb failure stress, but that 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.

Cebry, S. B. L., Ke, C.-Y & McLaskey, G. C. (2022) The Role of Background Stress State in Fluid-Induced Aseismic Slip and Dynamic Rupture on a 3-meter Laboratory Fault Journal of Geophysical Research: Solid Earth, 127, e2022JB024371. doi: 10.1029/2022JB024371

Invited talk at ERC TECTONIC/FEAR Seminar

2022-06-13T22:30:00+08:00

I gave a talk at the ERC TECTONIC/FEAR Seminar about our recent work on earthquake breakdown/fracture energy, following the ERC FEAR-TECTONIC Workshop on Earthquake Dynamics: Mechanical Work and Fracture Energy. Watch it on YouTube.

Ke, C.-Y., McLaskey, G. C. & Kammer, D. S. (2022) Earthquake breakdown energy scaling despite constant fracture energy. Nature Communications, 13, 1005. doi: 10.1038/s41467-022-28647-4

Ke, C.-Y., McLaskey, G. C. & Kammer, D. S. (2021) The Earthquake Arrest Zone. Geophysical Journal International, 224(1), 581-589. doi: 10.1093/gji/ggaa386

The ERC TECTONIC/FEAR Seminars on Earthquake Physics: Learning from lab earthquake prediction and underground fault stimulation to improve forecasts of tectonic fault activation

Featured in Cornell Chronicle

2022-03-08T00:00:00+08:00

Our latest paper is featured in Cornell Chronicle.

Ke, C.-Y., McLaskey, G. C. & Kammer, D. S. (2022) Earthquake breakdown energy scaling despite constant fracture energy. Nature Communications, 13, 1005. doi: 10.1038/s41467-022-28647-4

The Cornell Chronicle, Cornell’s source of official news since 1969, is part of University Relations. The site publishes daily news about research, outreach, events and the Cornell community.

Featured in Nature Communications

2022-02-24T00:00:00+08:00

Our latest paper is featured in Nature Communications Editors’ Highlights - Earth science.

Ke, C.-Y., McLaskey, G. C. & Kammer, D. S. (2022) Earthquake breakdown energy scaling despite constant fracture energy. Nature Communications, 13, 1005. doi: 10.1038/s41467-022-28647-4

The Editors’ Highlights pages aim to showcase the 50 best papers recently published in an area, and we routinely replace papers as more great research is published at Nature Communications.