`Subsidence rate' allows for either a constant subsidence rate, or the entry of a subsidence file name (filename.sub). If a subsidence file is specified, the user is essentially inputting the subsidence history at specific points (such as well locations).
Along with the subsidence rate, the user also determines which profile(s) should be used by specifying passive, foreland, or cratonic in `profile (name).'
Figures 9.a and 9.b illustrate a foreland and cratonic profile, respectively. The passive profile was illustrated in Figure 6.a, with the file runex.dat. For simplicity, each of these examples has sediment entering the system from the left edge only (right clastic flux is set to zero).
Figure 9.a Foreland basin profile. The library file used for this display is foreland.dat with skip lines set to 2 and a vertical exaggeration of 50.
Figure 9.bCratonic profile. Subsidence is constant along the profile. The library file used for this run is cratonic.dat with skip lines set to 2 and a vertical exaggeration of 50.
The user can specify subsidence that varies spatially and temporally through the use of subsidence files (labelled as filename.sub). Within the subsidence files are a series of `well' locations where the subsidence history is specified through time. the form of these well histories is that of a `backstripping' analysis where the depth to basement (or the base of the basin) is specified through time. Our vision is that the user will apply backstripping to a given basin and use those backstripping results as input into the forward model. Between the wells, linear interpolation is used to determine the subsidence history. In locations to the right or left of the last well (or if there is only one well), the subsidence of the last well is used up to the edge of the basin. Note, only vertical subsidence can be specified. Thus, the closest one can come to simulating a fault is to have two adjacent wells have very different subsidence histories as we have shown below.
Figures 10.a and 10.b show examples of images created using user-defined subsidence files. The subsidence files entered in the `subsidence rate' line to create the profiles in Figures 10.a and 10.b are shown below (subsid_ex1.sub & subsid_ex2.sub)
Example of subsidence file subsid1.sub
Well One:
0e3 0e3
-14e6 0.
0 500
Well Two:
100e3 100e3
-14e6 0.
0 500
Well Three:
101e3 101e3
-14e6 0.
0 1000
Well Four:
200e3 200e3
-14e6 0.
0 500
end: -1
Example of subsidence file subsid2.sub:
Well One:
-14e6 0.
-8e6 300
0 750
Well Two:
-14e6 0.
-8e6 300
0 750
Well Three:
-14e6 0.
-8e6 750
0 1200
Well Four:
-14e6 0.
-8e6 300
0 750
end: -1
Subsidence file notes:
1) The first line for each well is comprised of comments, followed by a colon
2) The second line is the horizontal position of the well
3) The following lines are age/depth pairs with the age in years measured from the present (therefore negative or 0). For example, 10 million years ago is -10e6.
4) Be sure that the first age in each well is equal to the starting time of the simulation
5) If the final age in each well is not zero, the depth at the most recent age will be used until t=0
6) Be sure to have a line space between each well
7) Be sure to end the subsidence file with the end line
Figure 10.a: Example of a subsidence profile generated by a user-defined subsidence file, subsid1.sub. The library file used in this run is subsid_ex1.dat with skip lines set to 3 and a vertical exaggeration of 50. In a crude sense this is meant to simulate a growth fault. Any number of subsidence histories, defined with "wells" at positions along the profile, can be specified.
Figure 10.b: Example of a subsidence profile generated by a user-defined subsidence file, subsid2.sub. (Note that for this example the subsidence rate varies through time.) In a crude sense this is meant to simulate a growth fault that becomes inactive. The library file used for this model run is subsid_ex2.dat with the skip lines set to 3, vertical exaggeration of 50.
