Clarification on Inter-Event vs Intra-Event Variability in Scenario GMF Outputs

[Ömer Faruk Kalaycı]

Hi OpenQuake Support Group,

I am analyzing ground-motion values and their corresponding scatter (ε) for any site. For this purpose, I am generating multiple ground-motion fields using a scenario calculation (single deterministic rupture).

In the output, the "sigma_epsilon.csv" file contains a "sig_inter_SA" column. However, since I am using a single deterministic rupture (only one event), I would expect the inter-event variability to be zero, and the scatter to come only from the intra-event variability (ϕ) component.

Therefore, I would like to confirm whether the reported scatter corresponds to ϕ, and how OpenQuake handles the decomposition into τ and ϕ in this scenario. 

Additionally, could you clarify how the total variability is computed, e.g

                                                            σ=sqrt(τ2+ϕ2)

Thanks,

Ömer Faruk Kalaycı

[Marco Pagani]

Hi OpenQuake Support Group,

I am analyzing ground-motion values and their corresponding scatter (ε) for
any site. For this purpose, I am generating multiple ground-motion fields
using a scenario calculation (single deterministic rupture).

In the output, the "sigma_epsilon.csv" file contains a "sig_inter_SA"
column. However, since I am using a single deterministic rupture (only one
event), I would expect the inter-event variability to be zero, and the
scatter to come only from the intra-event variability (ϕ) component.

It’s unclear why you would expect the engine to use inter-event variability == 0

Therefore, I would like to confirm whether the reported scatter corresponds
to ϕ, and how OpenQuake handles the decomposition into τ and ϕ in this
scenario.
Additionally, could you clarify how the total variability is computed, e.g

σ=sqrt(τ2+ϕ2)

Thanks,
Ömer Faruk Kalaycı

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