[GPlates-discuss] plotting relative plate velocities

[Christian.Heine at shell.com]

Christoph,

> I used the Zahirovic et al. model to extract plate velocities. I tried to
> create plots with relative plate movements, and followed the instructions
> from the tutorial.

This (https://docs.google.com/document/d/1xUHGu1N-nirc9t2srspdSOsmx0jrRsrBoJgWw5Ge0bI/pub) one?

[snip]

> Here my first plot, it shows convergence of Arabia and Eurasia. (It's
> based on an India-Eurasia-Convergence plot Sabin was kind enough to
> share, and which I could reproduce, too)

Attached my version which looks slightly similar but doesn't have the spikes at 27/16 Ma. This is for a point close to Kuweit.

> Looks great, but has these two excursions at 27 & 16 Ma, which I find
> geologically difficult. Is this an artifact? How would you deal with it?

You haven't mentioned whether you use a single point or the velocity domain points to achieve this. I think in the latter case, what could happen (and lead to the spikes) is if a plate boundary moves across your velocity domain point for a very short amount of time and you hence pick up velocities from a separate plate there. 

Depending on what you're trying to do it might be easier to digitise your points as 'standard' features and then use them for input for a new 'Calculated velocity fields' layer (simply add a new layer in the layer mgr) instead of the velocity domain points.

> Second, I tried to do the same plot for Arabia and India. Unfortunately
> sth went wrong here, and in the .xy export files it shows the wrong plate
> IDs. I tried it several times, but don't get it to work. Any idea is
> appreciated. Thanks and cheers,

Could be the same issue as above. Using the kinematics tool I can happily make vel magnitude vs time plots for ARA-IND. Try digitising a point and export vels from there.

HTH,
Christian


--
  Christian Heine, Ph.D.
  Upstream - Opportunity Identification (UPX/N/OH)
  Shell Intl. Exploration and Production B.V. 
  Carel van Bylandtlaan 5 | C05-01-B33
  2596 HP Den Haag, The Netherlands
 



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