Preserve H1/H2 ratio

[a06183]

Hi.

I am working on spectral matching through QuakeManager.

Currently, we are matching horizontal two-direction components.
I have a question regarding the “H1/H2 ratio”.

I plan to match H1 and H2 components to the same target spectrum.
At this time, I would like to select the Preserve H1/H2 ratio option.

I read the manual and found the following:

<GeoMean matching works by setting the same target for components H1 and H2 such that the resultant GeoMean is matched. With the "Preserve H1/H2 ratio" option selected, this is not true anymore." >

So, when matching, will the target spectrum for H1 and the target spectrum for H2 be different?

If it changes, what process will it change?

Thanks. Regards!

[mahmoud_hachem]

Yes, when you select the “Preserve H1/H2 ratio”, the H1 and H2 components' target spectra will be different, but the geomean will still be perfectly matched.
You can verify that the H1 & H2 targets are different by plotting the targets through the appropriate buttons on toolbar (e.g. using the "Comp Targets" button on the toolbar).

At each period, the target spectra for the two horizontal components H1 and H2 (Sa_H1_target and Sa_H2_target) are calculated such that the following equations are satisfied:
1. Sqrt(Sa_H1_target * Sa_H2_target) = Sa_geomean_target
2. Sa_H1_target/Sa_H2_target = Sa1_orig/Sa2_orig, where Sa1_orig and Sa2_orig are the component spectral accelerations for the original (unmatched) record components.

The two equations above are then solved for Sa_H1_target and Sa_H2_target