A global record section lines up the seismograms of one earthquake in order of…
PHYSICS · Multi-part · Fermi University Physics · Earth, Climate & Energy Physics · Seismology, tectonics and geodynamics · Seismology, tectonics and geodynamics
The Solid Earth, Ch Rays and travel times: from arrivals to a layered planet
Problem
A global record section lines up the seismograms of one earthquake in order of epicentral distance. Besides direct P and direct S, three later branches are picked:
((a)) a P-type arrival that comes in after direct P at every distance out to about 100∘, its delay behind P shrinking as distance grows;
((b)) an arrival that crosses direct S near 80∘ and comes in ahead of it at larger distances;
((c)) strong P-type arrivals beyond about 142∘, later than a continued direct P curve would put them. Name the phase on each branch, and give in one sentence each the feature of its path that places it there.