Number of ground motion fields

[Cellule Verte]

Hello.

Is there anyone who could explain how  the two parameters truncated_level and  number_of_ground_motion_fields   are used in the calculation of ground motion for a single fault rupture  ? 

Thanks in advance,

Philippe Rosset

McGill University.

[Marco Pagani]

I suppose you are working with scenario analysis (e.g. https://github.com/gem/oq-engine/blob/master/demos/hazard/ScenarioCase2/job.ini#L27).

The truncation_level variable controls the normal distribution of the logarithm of ground motion. For example, if you set it to 3, OQ will assume that the ground-motion follows a double truncated gaussian comprised between -3*standard devs and +3*standard devs.

The number_of_ground_motion_fields variable controls the number of fields (that is the spatial distribution of the shaking around the rupture you are modelling). Each field represents a possible (spatial) distribution of the shaking obtained by taking account the variability of ground-motion as just described.

See also section 3.4.4 in the OQ manual. https://docs.openquake.org/manuals/OpenQuake%20Manual%20%28latest%29.pdf

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