Site Specific Ground Motion Hazard Analysis-Eastern US

[moe333]

Hi All,

I'm trying to perform a Site Specific Ground Motion Hazard Analysis in West Virginia. I have done these previously in California where there are many discrete faults but that isn't the case in West Virginia.

Is this analysis typically performed in this part of the country to attempt to reduce the seismic design category as is the case in California?

My problem is: what fault would I use for the deterministic part of the analysis? The discrete faults are 100's of km's away where attenuation relationships are not considered valid. The only one valid for the Eastern US I have access to is Toro (97). Is this a commonly used relationship in this part of the country? Most of the probabilistic seismicity based on the 2008 USGS deaggregation is from gridded sources. Is it customary to use the gridded source with the R and M as shown in the 2008 USGS deaggregation as a discrete fault in the deterministic analysis?

The other smaller problem is that I'm using the 2008 USGS Deaggregation for the probaibilistic part of the analysis. It will only provide values for Vs-30 of Site Class A and B/C, whereas I need it for Site Class C. I'm assuming I can just apply Fa and Fv coefficients to get to a Site Class C?

Thanks, any suggestions are appreciated.

 

[moe333]

One approach I am considering is to use the Deterministic Lower Limit as the Deterministic MCE as specified in ASCE 7-05. However, this may be unconservative and I'm not sure how the reviewers would perceive it.

 

[dgillette]

I know it's frowned upon, but consider cross posting at Seismology Engineering, since that may draw a mostly different audience.

I've got to ask, what are you building in West By God Virginia that requires site-specific hazard analysis?

DRG

 

[moe333]

It's a 2 story fire station. The site is right on the border of a Seismic Design Category so if I can get a very small reduction in the IBC parameters (through the site specific hazard analysis)the Seismic Design Category drops to the lower category resulting in much lower costs.

 

[moe333]

I figured out that the attenuation relationships used for the Eastern US are typically applicable to 1000 km. However, the the lower limit on the deterministic response spectrum is high enough that the probabilistic response spectrum will govern when you are far from seismic sources.....mystery solved.