1. Martijn van den Ende Jianye Chen Jean-Paul Ampuero André Niemeijer
Earthquake and slow-slip nucleation investigated with a micro-physics based seismic cycle simulator
Martijn van den Ende Jianye Chen Jean-Paul Ampuero André Niemeijer

2. Problem: extrapolation of rate-and-state
Scholz (2002)
Rate-and-state friction is a convenient description of fault rock friction
Natural faults are more complex than rate-and-state
Empirical nature of rate-and-state limits extrapolation
Example: (𝑎−𝑏) varies with 𝑇, 𝑉, 𝜎 𝑛
𝜇= 𝜇 ∗ +𝑎 ln 𝑉 𝑉 ∗ + 𝑏 ln 𝜃 𝜃 ∗

3. Problem: extrapolation of rate-and-state
Lab
Model
Field
Understanding of friction in terms of mechanisms: micro-physics
In recent years, a number of physics-based models have been proposed (e.g. Ikari et al. 2016; Niemeijer & Spiers, 2007; Putelat et al. 2011)
Micro-physical models are limited in geometry/complexity
Numerical seismic cycle simulators based on rate-and-state friction
Bridge gap between laboratory and nature: combine models
gap

4. Approach
Implementation of CNS micro-physical model into QDYN to simulate seismic cycle
Confirm that the micro-physical model produces rate-and-state characteristics
Aim: investigate the effect of fluid-rock interactions on depth of seismogenic zone

5. Experimental observations
halite-muscovite mixtures, 𝜎 𝑛 = 5 MPa
V-weakening
V-strengthening
V-strengthening
Dynamic
weakening

6. After Shimamoto (1986) Niemeijer & Spiers (2006) Bos et al. (2000)

7. Chen-Niemeijer-Spiers (CNS) Model
Conceptual ideas Niemeijer & Spiers (2007) and Chen & Spiers (2016)

8. Chen-Niemeijer-Spiers (CNS) Model
Conceptual ideas Niemeijer & Spiers (2007) and Chen & Spiers (2016)
Granular flow + Pressure solution
Microstructural state:
Porosity

9. Boundary Conditions & Geometry Gouge material properties
1 𝑘 d𝜏 d𝑡 =ℎ 𝛾 𝑖𝑚𝑝 − 𝛾 𝑝𝑠 + 𝛾 𝑔𝑟
d𝜑 d𝑡 =− 1−𝜑 𝜀 𝑝𝑠 − tan 𝜗 𝛾 𝑔𝑟
𝜀 𝑝𝑠 , 𝛾 𝑝𝑠 , 𝛾 𝑔𝑟 =𝑓(𝜏,𝜑)
Boundary Conditions & Geometry
Normal stress
Load-point velocity
Fault zone thickness
Degree of localisation
Gouge material properties
Nominal grain size
Pressure solution kinetics (T-dep.)
Grain boundary friction coefficient

10. Examples CNS model
Steady-state behaviour CNS
After Shimamoto (1986)

11. Examples CNS model Velocity step test
Forward RSF models with CNS parameters

12. CNS + QDYN CNS model in essence describes behaviour of spring-block
QDYN: Quasi-Dynamic Earthquake Simulator
Features:
Open-source on Github
Spring-block, 2D and 3D (non-planar) faults
Adaptive time-stepping
Custom fault rheology
© Y. Luo

13. Crustal strike-slip model
Similar to Tse & Rice (1986), Lapusta & Rice (2003)
1D fault embedded in 2D medium, shear modulus 𝐺=30 GPa
External loading velocity: 𝑣= 10 −9 m/s≈30 mm/yr
Uniform geothermal gradient of 25 K/km
Quartz pressure solution kinetics (temperature-dependent)

14. Crustal strike-slip model
Similar to Tse & Rice (1986), Lapusta & Rice (2003)
1D fault embedded in 2D medium, shear modulus 𝐺=30 GPa
External loading velocity: 𝑣= 10 −9 m/s≈30 mm/yr
Uniform geothermal gradient of 25 K/km
Quartz pressure solution kinetics (temperature-dependent)
For each fault segment:
Pressure solution kinetics
Grain size
Localisation
Normal stress
Temperature
Each time-step, solve for shear stress and gouge porosity (CNS model)

15. Steady-state behaviour
𝑉 𝑙𝑝 m/s
10 −10
10 −9
10 −8

16. At V= 10 −9 m/s

17. At V= 10 −9 m/s

18. At V= 10 −9 m/s

19. At V= 10 −9 m/s

20. At V= 10 −9 m/s

21. Steady-state behaviour

22. At V= 10 −9 m/s

23. Take-home messages
Lower geothermal gradient extends the seismogenic zone downward, and increases event size
Seismic ruptures may traverse the brittle-ductile transition
CNS can explain natural seismicity from micro-physical perspective
Use CNS/QDYN implementation for studying seismic cycle with good basis for extrapolation
Opportunity for new insights in EQ mechanics

24. More details in…
Chen & Spiers (2016), JGR: Solid Earth, doi: /2016JB poster in this session! (X2.107)
Niemeijer & Spiers (2006), Tectonophysics, doi: /j.tecto
Niemeijer & Spiers (2007), JGR, doi: /2007JB005008
QDYN: