[CIG-LONG] Faults do not depart away from the axis

[Garrett Apuzen-Ito]

Hi Taichi,

  I haven't followed all of your last few conversations, but here are a couple of suggestions.
(1) You should check the rate that the dike zone is widening.  If it is widening and the fault(s) is on the side of the dike zone then the fault should be moving, except if the rate the dike is opening is about half the spreading rate (i.e., M=0.5, see Buck et al. 2005 or Behn & Ito 2008).  If the dike is NOT opening at half the spreading rate then the fault will be moving but I suppose it is possible that it is lengthening toward the ridge axis and therefore appears to be stationary.  
(2) I originally set vz=0 on the top and bottom of the dike so that all of the imposed divergence is accommodated by the dike widening.  This is the best way to control the rate of dike widening.  But this might prevent the dike from moving up in down naturally with the surrounding material.  Did you try only setting vz=0 on the bottom and not specifying vz (or vx) on the top of the dike?  

Garrett

----- Original Message -----
From: Taichi SATO <taichix at aori.u-tokyo.ac.jp>
Date: Tuesday, June 8, 2010 4:27 pm
Subject: [CIG-LONG] Faults do not depart away from the axis
To: cig-long at geodynamics.org

> Hi,
> 
> I still have problem with the dike hill of 
> mid-ocean ridge modeling.
> But I found another problem. Faults initiated at 
> the axis do not depart away from the axis.
> 
> I think this is the same problem written in the 
> supplemental paper of the Buck et al., 2005, Nature.
> I picked up the sentences from the paper,
> 
> ---------
>   Accumulation of plastic deformation in the dyke 
> tends to lock the location of tectonic faulting at 
> the base of the dyke and does not allow the faults 
> to depart away from the axis as is observed. To 
> solve this problem strain accumulation in the dyke 
> is limited to smaller amount than the initial 
> weakening necessary to form a fault (5 MPa of 
> cohesion reduction). This way a fault forms and 
> can move away from the axis.
> ----------
> 
> I have no idea how to apply this solution to the Gale.
> Would you give me some suggestion?
> 
> Sincerely,
> 
> Taichi
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