[CIG-SEISMO] [Specfem3D Cartesian]- Using a CMTSOLUTION source to trigger a critically-stressed fault

Tue Apr 10 00:01:41 PDT 2018

Dear Ge,

Currently, the implementation is such that all the fault in a particular
simulation should be either Kinematic or Dynamic.
Nevertheless, you can run a kinematic simulation, observe the stress
changes on the other fault and setup a dynamic rupture simulation based on
the updated stresses.

Btw, what is the magnitude of the point source (CMTSOLUTION) you have put
in your simulation?

Best,
Surendra

___________
*Surendra Nadh Somala*
Assistant Professor
Department of Civil Engineering (Block-E, 208)
Indian Institute of Technology (IIT) Hyderabad
Kandi, Sangareddy
Telangana, India - 502285
Phone : +91 (0)40 2301-8457
http://civil.iith.ac.in/surendra/

On Tue, Apr 10, 2018 at 1:08 AM, Ge Li <ge.li2 at mail.mcgill.ca> wrote:

> Hi Kangchen and Dimitri,
>
> Thanks for your reply!
>
> Kangchen, can you give me more explanations on ‘fault-node splitting’?
>
> Do you mean the split-node technique used during the mesh process? I
> followed the
>
> instructions provided in the specfem3d manual to create a Cubit mesh file.
> The
>
> mesh works well for a ‘step-over’ scenario and I did observe the  dynamic
> stress transfer.
>
> Back to the test mentioned in my previous email, where I put a point
> source
>
> (Mw~6 Right-lateral strike slip) about only 1km away from the fault
> surface. I also observed
>
> stress changes, but with a magnitude of ~  0.0682Pa. Considering the
> initial stress level of
>
> 82.1MPa, I suspected these stress changes are numerical?
>
>
>
> Also is it possible to implement both dynamic and kinematic fault in a
> model, i.e. one fault is
>
> Kinematic and the other one is dynamic.
>
>
>
> Thanks !
>
> Best regards,
>
> Ge
>
>
>
>
>
> *From: *Kangchen Bai <kbai at caltech.edu>
> *Date: *Monday, April 9, 2018 at 1:12 PM
> *To: *Dimitri Komatitsch <komatitsch at lma.cnrs-mrs.fr>
> *Cc: *<cig-seismo at geodynamics.org>, Ge Li <ge.li2 at mail.mcgill.ca>,
> Surendra Nadh Somala <surendra at iith.ac.in>, <ampuero at geoazur.unice.fr>
> *Subject: *Re: [CIG-SEISMO] [Specfem3D Cartesian]- Using a CMTSOLUTION
> source to trigger a critically-stressed fault
>
>
>
> Hi Ge,
>
>
>
> Triggering a dynamic rupture with a point source is do-able with the code.
> You should see dynamic stress changes as the wave goes across the fault.
>
>  I actually did similar things before by mistake --- I forgot to turn off
> the point source when doing a dynamic rupture simulation and see the
> circular stress pattern on the fault.
>
>
>
> We also did the work of one fault rupture triggering another using the
> code (See Bai & Ampuero 2017
>
> https://doi.org/10.1002/2017JB014848
> <https://doi.org/10.1002/2017JB014848%20>
>
>  ), the stress transfer is not a problem as is shown in Fig 6 & 7.
>
>
>
> If you do not see stress changes, there must be something wrong with the
> settings.
>
> I suspect the most plausible scenario is that the fault node is not split
> in which case the stress remain constant anyhow.
>
> Let me know if you have more questions.
>
>
>
> Best,
>
> Kangchen
>
>
>
> On Mon, Apr 9, 2018 at 7:21 AM, Dimitri Komatitsch <
> komatitsch at lma.cnrs-mrs.fr> wrote:
>
>
> Dear Ge Li,
>
> Thank you very much for your email and for your interest in the work of
> the community around the package.
>
> Yes, if you want to mimic an extended source using a kinematic source
> model, you can use many CMTSOLUTION sources that are triggered at different
> times and at slightly different locations (see e.g. the discussion about
> extended sources around equation (A12) of http://komatitsch.free.fr/
> preprints/GJI_1999_figure16_error_fixed_equation3_typo_fixed.pdf, and the
> way we mimic a Hamming quasi-plane wave using 1000 such sources in
> http://komatitsch.free.fr/preprints/Ultrasonics_Moysan_2016.pdf figure 5).
>
> If you want a dynamic rupture source model, i.e. something more
> sophisticated, the package can do that based on the great work of Jean-Paul
> Ampuero, Surendra Nadh Somala, Kangchen Bai and other people in the
> community, they can give you more details (they will know much more about
> this than I do :-)
> Let me thus cc them.
>
> Best regards,
> Dimitri.
>
> On 04/05/2018 03:00 AM, Ge Li wrote:
>
> To Whom It May Concern:
>
> I’m a PhD Candidate in geophysics at McGill University. Currently I’m using
>
> Specfem3D Cartesian for my research.
>
> I’m wondering is it possible to trigger an earthquake on a fault using a
> CMTSOLUTION source?
>
> I tried several simulations by setting a critically stressed fault and a
> CMTSOLUTION point source.
>
> The source (Mw~6 Right-lateral strike slip) was located about only 1km
> away from the fault surface.
>
> But it turned out the stresses on the fault surface(dynamic
> slip-weakening) remain unchanged.
>
> Based on these tests, I supposed that a CMTSOLUTION won’t change the
> stress level on a fault surface. Is it correct?
>
> Or did I miss something here?
>
> Thanks! I’m looking forward to your reply!
>
> --
>
> *Ge Li*
>
> /Ph.D. Candidate/
>
> /Department of Earth & Planetary Science, /
>
> /McGill University/
> <https://maps.google.com/?q=University/+/3450+University+Street/+/Montreal,+QC,+Canada+/+/H3A&entry=gmail&source=g>
>
> /3450 University Street/
> <https://maps.google.com/?q=University/+/3450+University+Street/+/Montreal,+QC,+Canada+/+/H3A&entry=gmail&source=g>
>
> /Montreal, QC, Canada /
> <https://maps.google.com/?q=University/+/3450+University+Street/+/Montreal,+QC,+Canada+/+/H3A&entry=gmail&source=g>
>
> /H3A
> <https://maps.google.com/?q=University/+/3450+University+Street/+/Montreal,+QC,+Canada+/+/H3A&entry=gmail&source=g>
> 0E8/
>
> /ge.li2 at mail.mcgill.ca <mailto:ge.li2 at mail.mcgill.ca>/
>
>
>
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>
>
> --
> Dimitri Komatitsch, CNRS Research Director (DR CNRS)
> Laboratory of Mechanics and Acoustics, Marseille, France
> http://komatitsch.free.fr
>
>
>
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