Hi, I am in Year 12 and I am studying earthquake engineering for an extended project qualification and have a couple of questions I need answering if possible.
Is there more friction at a oceanic/continental convergent plate boundary ( as one is moving up due to obduction, and one is moving down due to subduction) because the plates have a greater relative velocity ( they are moving in opposite directions) than at a continental/continental plate boundary where both plates are moving upwards due to obduction?
If there is a significant difference in friction, would this cause the oceanic/continental convergent plate boundary to generate more powerful earthquakes than a continental/continental convergent plate boundary.
And can this principle be applied to transform fault boundaries, ( ie because the plates are moving in opposite directions friction is greater than if the plates moved in the same direction or if only one plate moved?)
Basically to what extent is my theory correct?
Is there more friction at a oceanic/continental convergent plate boundary ( as one is moving up due to obduction, and one is moving down due to subduction) because the plates have a greater relative velocity ( they are moving in opposite directions) than at a continental/continental plate boundary where both plates are moving upwards due to obduction?
If there is a significant difference in friction, would this cause the oceanic/continental convergent plate boundary to generate more powerful earthquakes than a continental/continental convergent plate boundary.
And can this principle be applied to transform fault boundaries, ( ie because the plates are moving in opposite directions friction is greater than if the plates moved in the same direction or if only one plate moved?)
Basically to what extent is my theory correct?
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I would say that a transform fault boundary has the greatest amount of friction, as convergent plate boundaries have subduction which will help reduce the friction. The best evidence for that is the Franciscan Terrane blueschist in California.
You should be careful with the word "obduction" as normally that does not happen at convergent boundaries. It has happened in the past (eg, Newfoundland, Cyprus, and Oman), but is not occurring now. Subduction means one plate slides below the other, and obduction means one plate slides above the other. Normally a continental-oceanic boundary has subduction with the denser oceanic plate sliding below the lighter continental plate, and a continental-continental boundary simply has collision, where neither plate gives way due to equivalent specific gravities, eg Himalayas.
It doesn't matter if the plates "moved in the same direction or if only one plate moved" - it is relative movement that determines the type of plate margin and the associated stress and friction.
You should be careful with the word "obduction" as normally that does not happen at convergent boundaries. It has happened in the past (eg, Newfoundland, Cyprus, and Oman), but is not occurring now. Subduction means one plate slides below the other, and obduction means one plate slides above the other. Normally a continental-oceanic boundary has subduction with the denser oceanic plate sliding below the lighter continental plate, and a continental-continental boundary simply has collision, where neither plate gives way due to equivalent specific gravities, eg Himalayas.
It doesn't matter if the plates "moved in the same direction or if only one plate moved" - it is relative movement that determines the type of plate margin and the associated stress and friction.