# Finn Model - ff\_latency parameter estimation

**URL:** <https://forum.itascainternational.com/t/finn-model-ff-latency-parameter-estimation/1718>\
**Category:** FLAC\
**Created:** [September 27, 2024, 2:37pm UTC](https://forum.itascainternational.com/t/finn-model-ff-latency-parameter-estimation/1718 "2024-09-27T14:37:21Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![MiguelN](https://avatars.discourse-cdn.com/v4/letter/m/6f9a4e/32.png) [@MiguelN](https://forum.itascainternational.com/u/MiguelN)\
**Post date:** [September 27, 2024, 2:37pm UTC](https://forum.itascainternational.com/t/finn-model-ff-latency-parameter-estimation/1718/1 "2024-09-27T14:37:21Z")

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Hi everyone.

Question. For Finn Model, in dynamic analysis, how is the best practice to calculates or defines the ff\_latency parameter in a seismic analysis? Thanks in advance.

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**Author:** ![jwang](https://avatars.discourse-cdn.com/v4/letter/j/b782af/32.png) [@jwang](https://forum.itascainternational.com/u/jwang)\
**Post date:** [September 30, 2024, 5:24pm UTC](https://forum.itascainternational.com/t/finn-model-ff-latency-parameter-estimation/1718/2 "2024-09-30T17:24:37Z")

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The ‘ff\_latency’ is the minimum of timesteps before a reversal is detected and this threshold number of timestep was introduced in the model to circumvent unphysical pore pressure generation introduced by ratcheting. A value of 50 for the property seems reasonable for most cases when potential liquefaction is expected. Latency property can be set to a very high value at static stage to prevent the liquefaction calculation from being activated, when switching materials to the Finn model, to make sure that the model is still at an equilibrium state before commencing the dynamic simulation.