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Table 1 Parameters used in this study

From: Subduction initiation from a stagnant lid and global overturn: new insights from numerical models with a free surface

   Regional model Global model  
   Non-dimensional Dimensional Non-dimensional Dimensional  
Parameter Symbol value value value value Units
Mantle depth D 1 600 1 2890 km
Reference viscosity η 0 1 6.92×1027 1 1023 Pa s
Surface Ra number R a H,0 0.1 -    -
Internal Ra number R a T,0    106 - -
Frank-Kamenetskii parameter θ 60 -    -
Stress exponent n 1 -    -
Gravitational acceleration g - 9.81 - 9.81 ms −2
Thermal conductivity k - 3 - 3 Wm −1 K −1
Thermal diffusivity κ 1 10−6 1 10−6 m 2 s −1
Thermal expansivity α - 3×10−5 - 3×10−5 K −1
Temperature gradient Δ T - 2500 - 2500 K
Reference density ρ 0 - 3300 - 3300 kg m −3
Heat capacity C p 0 - 1200 - 1200 Jkg −1 K −1
Internal heating rate H 1 6.31×10−12 20 5.44×10−12 Wkg −1
Constant yield stress σ y,const variable b variable b variable b variable b MPa
Yield stress gradient Δ σ y variable b variable b variable b variable b -
Friction coefficient μ    0.09 a - -
Cohesion C    100 6.34×105 Pa
Activation energy E act    11.55 240 kJmol −1
Activation volume V act    4.0 8.8878×10−7 m 3mol
Upper viscosity cutoff η max 102 η 0 6.92×1029 105 η 0 1028 Pa s
Lower viscosity cutoff η min 10−8 η 0 6.92×1019 10−4 η 0 1019 Pa s
Sticky-air layer: c  
Thickness d st 0.05 30 0.05 145 km
Viscosity η st 10−8 η 0 6.92×1019 10−2 η 0 1021 Pa s
C-condition d C Stokes 1.5×10−7 - 0.175 - -
  1. aIndicated is standard setup; parameter variation is mentioned separately
  2. bFor actual values, see Tables 2 and 3
  3. cIf applied
  4. dIndicates suitable free-surface approximation with sticky-air approach if C Stokes1 (Crameri et al. 2012a)