Different segments in sections#
Slabs and faults may not only vary in depth, but may also vary a lot laterally. To accomplish this in the world builder, we will need to introduce the term “sections”. Sections are a way to overwrite the segments at a specified coordinate.
Note
One way of thinking about segments and sections is that together they form a 2D grid. The segments form one axis (down dip) and the sections form the other axis (along strike).
Sections replace all the segments at that coordinate, and it is required that all sections have the same number of segments.
In this case we are going to change the values for the first coordinate, which is coordinate 0. We keep the length the same as the default first segment (compare lines 48 and 75), but we make the second segment a bit shorter (compare lines 52 and 58). We also do not change the feature composition model in the first segment, but we do change it in the second segment, where we set it equal to composition of the lower part of the oceanic plate for the whole thickness of the segment (line 59).
43 {
44 "model":"subducting plate", "name":"Slab", "dip point":[0,0],
45 "coordinates":[[1500e3,1000e3],[1600e3,350e3],[1500e3,0]],
46 "segments":
47 [
48 {"length":300e3, "thickness":[100e3], "angle":[0,60],
49 "composition models":[
50 {"model":"uniform", "compositions":[3], "max distance slab top":50e3},
51 {"model":"uniform", "compositions":[2], "min distance slab top":50e3}]},
52 {"length":500e3, "thickness":[100e3], "angle":[60,20]}
53 ],
54 "sections":
55 [
56 {"coordinate":0,
57 "segments":[{"length":300e3, "thickness":[100e3], "angle":[0,60]},
58 {"length":400e3, "thickness":[100e3,50e3], "angle":[60]}],
59 "composition models":[{"model":"uniform", "compositions":[1]}]}
60 ],
61 "temperature models":[{"model":"plate model", "density":3300, "plate velocity":0.02}],
62 "composition models":[{"model":"uniform", "compositions":[2]}]
63 }
1{
2 "version": "1.0",
3 "coordinate system":{"model":"cartesian"},
4 "features":
5 [
6 {
7 "model":"mantle layer", "name":"upper mantle", "max depth":660e3,
8 "coordinates":[[-1000e3,0],[-1000e3,1000e3],[3000e3,1000e3],[3000e3,0]],
9 "composition models":[{"model":"uniform", "compositions":[4]}]
10 },
11 {
12 "model":"oceanic plate", "name":"Overriding Plate", "max depth":100e3,
13 "coordinates":[[0,0],[0,1000e3],[1500e3,1000e3],[1600e3,350e3],[1500e3,0]],
14 "temperature models":
15 [
16 {"model":"half space model", "max depth":100e3, "spreading velocity":0.04,
17 "ridge coordinates":[[[400e3,-1],[-100e3,2000e3]]]}
18 ],
19 "composition models":[{"model":"uniform", "compositions":[0], "max depth":50e3}]
20 },
21 {
22 "model":"continental plate", "name":"Passive margin", "max depth":[[200e3]],
23 "coordinates":[[-1000e3,0],[-1000e3,1000e3],[0,1000e3],[0,0]],
24 "temperature models":
25 [
26 {"model":"linear", "max depth":[[100e3],[200e3,[[-250e3,0],[-750e3,1000e3]]]]}
27 ],
28 "composition models":
29 [
30 {"model":"uniform", "compositions":[3],
31 "max depth":[[100e3],[200e3,[[-250e3,0],[-750e3,1000e3]]]]},
32 {"model":"uniform", "compositions":[1],
33 "min depth":[[100e3],[200e3,[[-250e3,0],[-750e3,1000e3]]]]}
34 ]
35 },
36 {
37 "model":"oceanic plate", "name":"Subducting Oceanic plate", "max depth":100e3,
38 "coordinates":[[2000e3,0],[2000e3,1000e3],[1500e3,1000e3],[1600e3,350e3],[1500e3,0]],
39 "temperature models":[{"model":"linear", "max depth":100e3}],
40 "composition models":[{"model":"uniform", "compositions":[3], "max depth":50e3},
41 {"model":"uniform", "compositions":[1], "min depth":50e3}]
42 },
43 {
44 "model":"subducting plate", "name":"Slab", "dip point":[0,0],
45 "coordinates":[[1500e3,1000e3],[1600e3,350e3],[1500e3,0]],
46 "segments":
47 [
48 {"length":300e3, "thickness":[100e3], "angle":[0,60],
49 "composition models":[
50 {"model":"uniform", "compositions":[3], "max distance slab top":50e3},
51 {"model":"uniform", "compositions":[2], "min distance slab top":50e3}]},
52 {"length":500e3, "thickness":[100e3], "angle":[60,20]}
53 ],
54 "sections":
55 [
56 {"coordinate":0,
57 "segments":[{"length":300e3, "thickness":[100e3], "angle":[0,60]},
58 {"length":400e3, "thickness":[100e3,50e3], "angle":[60]}],
59 "composition models":[{"model":"uniform", "compositions":[1]}]}
60 ],
61 "temperature models":[{"model":"plate model", "density":3300, "plate velocity":0.02}],
62 "composition models":[{"model":"uniform", "compositions":[2]}]
63 }
64 ]
65}
Basic Starter Tutorial section 15 high resolution result. This has 8 times the resolution then the grid file above. Note that the part of the slab on the far side now has a different composition and angle.#