4.6. Practicality — Modified Cloud Analysis

imselection.compute_practicality_mca(cloud_dict)[source]

Practicality measure from a Modified Cloud Analysis result.

Practicality = slope b from the log-linear regression log(EDP) = b₀ + b · log(IM). A higher slope indicates a stronger IM–EDP correlation and therefore a more practical intensity measure.

Parameters:

cloud_dict (dict) – Output of postprocessor.process_mca_results.

Returns:

dict with keys
* 'b_slope' — regression slope b (higher is better)
* 'method' — 'MCA'

Theoretical Background

Practicality measures how strongly the structural demand responds to the intensity measure (Luco and Cornell, 2007): the steeper the IM–EDP relation, the more a change in IM is reflected in the demand, and the more practical the IM.

Definition

For MCA it is the slope \(b\) of the log-linear cloud regression:

\[\ln(\text{EDP}) = b_0 + b\,\ln(\text{IM})\]

A higher \(b\) indicates a stronger IM–EDP correlation.

Example

from openquake.vmtk.imselection import imselection

ims = imselection()
# cloud_dict is the output of postprocessor.process_mca_results()
result = ims.compute_practicality_mca(cloud_dict)
print(f"Practicality (slope b) = {result['b_slope']:.4f}")