Central Japan Triple Junction revisited

We show that the two‐dimensional kinematic discussion of McKenzie and Morgan's TTT‐type triple junction is not sufficient, as it ignores the interaction of the sinking plates. We derive a relation for the three‐dimensional existence of TTT triple junctions and show that it is satisfied at the unstable central Japan triple junction. We then use the geometry of the subducting Pacific plate beneath the Philippine Sea and Eurasian plates to show that the present situation did not hold before about 3 Ma. Before that time, the triple junction was probably located north of the present one and very close to the pole of relative motion. Finally, we discuss the geological implications of this model.