# The spatial and time distribution of the change in tractions
**URL:** https://community.geodynamics.org/t/the-spatial-and-time-distribution-of-the-change-in-tractions/1759
**Category:** PyLith
**Created:** [March 26, 2021, 8:15am UTC](https://community.geodynamics.org/t/the-spatial-and-time-distribution-of-the-change-in-tractions/1759 "2021-03-26T08:15:25Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@WangPu-171](https://community.geodynamics.org/u/WangPu-171)
#### Post date: [March 26, 2021, 8:15am UTC](https://community.geodynamics.org/t/the-spatial-and-time-distribution-of-the-change-in-tractions/1759/1 "2021-03-26T08:15:25Z")
Dear,
I run the example of dynamic fault with slip-Weakening friction in 2D Bar, and notice we can add a change of tractions in different time on the fault. If my fault is very long, how can i add the spatial and time distribution of the change in tractions on the fault interfaces.
Very thanks!
---
### Author:  [@baagaard](https://community.geodynamics.org/u/baagaard)
#### Post date: [March 26, 2021, 6:37pm UTC](https://community.geodynamics.org/t/the-spatial-and-time-distribution-of-the-change-in-tractions/1759/2 "2021-03-26T18:37:23Z")
See section 6.4.5.2 of the PyLith v2.2.1 or v2.2.2 manual, including Table 6.11.
---
### Author:  [@WangPu-171](https://community.geodynamics.org/u/WangPu-171)
#### Post date: [March 28, 2021, 4:09am UTC](https://community.geodynamics.org/t/the-spatial-and-time-distribution-of-the-change-in-tractions/1759/3 "2021-03-28T04:09:56Z")
Very thanks, i see the Table 6.11 and run the example of step19 - Time-Dependent Surface Load, but i still puzzle that the second parameter of “th\_change.filename” is a ratio of db\_change, it maybe not the change of tractions in different spatial and time, how can i make different tractions in every part of fault and in every time step?
---
### Author:  [@baagaard](https://community.geodynamics.org/u/baagaard)
#### Post date: [March 28, 2021, 8:37pm UTC](https://community.geodynamics.org/t/the-spatial-and-time-distribution-of-the-change-in-tractions/1759/4 "2021-03-28T20:37:12Z")
The expression for the time dependence is the same as that used for the other boundary conditions (equation 6.1 in section 6.2). The shape of the temporal variation is uniform, but the amplitude and starting times can vary spatially. It you want something more complicated, you would have to implement it yourself.
---
### Author:  [@WangPu-171](https://community.geodynamics.org/u/WangPu-171)
#### Post date: [March 29, 2021, 2:22am UTC](https://community.geodynamics.org/t/the-spatial-and-time-distribution-of-the-change-in-tractions/1759/5 "2021-03-29T02:22:38Z")
Oh, I think that “TimeHistory” need to be optimized if i don’t want to use uniform shape of the temporal variation. Very thanks for your help.