 Solution

ID: past-exam-of-the-year-2-of-the-earth-sciences-geology-course-of-the-university-of-oxford/2022/paper-1/6/c/ii/solution

For a converted lower-layer S wave head wave, set the transmitted S angle to

9 0^{\circ}

\frac{s i n i _{c, S}}{V _{P 1}} = \frac{1}{V _{S 2}}, i_{c, S} = arcsin \frac{1500}{2000} = 48.5 9^{\circ} .

This is possible because

V_{S 2} > V_{P 1}

. It is the incident P angle needed for the converted SV branch to become tangential, not an S incident angle in layer 1.

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