Epicentral distance reached by nearly horizontally starting P waves for a focal depth of 300km and various depth samplings. The right plot is acloseup of the left one, showing that Δ(α) can have a quite complex structure near α=90°
The above plot was produced using the following commands (and a few manual adjustments):
figure(1);
clf;
hold on;
h=300;
dz=0.01;
[dist,depth,rayparm,angles]=mkdepthbydist(iasp91_1km,h,dz,'P');
[angles,sorter]=sort(angles);
dist=dist(sorter);
plot(angles,dist,'k-');
[dist,depth,rayparm,angles]=mkdepthbydist(iasp91_10km,h,dz,'P');
[angles,sorter]=sort(angles);
dist=dist(sorter);
plot(angles,dist,'g-');
[dist,depth,rayparm,angles]=mkdepthbydist(iasp91_50km,h,dz,'P');
[angles,sorter]=sort(angles);
dist=dist(sorter);
plot(angles,dist,'b-');
[dist,depth,rayparm,angles]=mkdepthbydist(iasp91_100km,h,dz,'P');
[angles,sorter]=sort(angles);
dist=dist(sorter);
plot(angles,dist,'m-');
[dist,depth,rayparm,angles]=mkdepthbydist(iasp91_100km_sph,h,dz,'P');
[angles,sorter]=sort(angles);
dist=dist(sorter);
plot(angles,dist,'r-');
hold off;
legend('1km flat','10km flat','50km flat','100km flat','100km spherical');
box on
grid on
xlabel('Take Off Angle [deg]');
ylabel('Epicentral Distance [deg]');
title('Phase: P, Focal Depth: 300km');
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