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Determination of the Present Day Relative Motion on the Peru-Chile Trench


For this, we construct a spherical triangle (a triangle drawn on the surface of a sphere). The triangle has three vertices, at the Geographical North Pole (N), the Euler Pole (P) for the motion we are interested in, and at the point (X) for which we want to calculate that motion. Here is an example triangle:

All measurements in this triangle are made in degrees and each of the triangle’s sides is a great circle. The vector, v, is the velocity at point X.


Calculate the present day relative motion at 28°S, 71°W on the Peru-Chile Trench using the Nazca-South America rotation pole (56°N, 94°W, =7.6x10-7 degrees/yr). Remember the sign convention: latitude N is positive, S negative, longitude E is positive, W negative.


This question belongs to geophysics and discusses about construction of spherical triangle and to determine the present day relative motion on the Peru-Chile Trench.

Total word count: 130


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