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Re: USGS Ground Motion Tool

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David,

It goes to Site Class B by default; you need to go to "Calculate SM and SD values" and choose Site Class D option on the right.

 
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Steve Gordin SE
Irvine CA



David Merrick, Structural Engineer, Merrick Group wrote:
 The USGS Ground Motion Program gave me a Site Class "B" where my common sense told me that was wrong and found that it is most likely a "D" Site Class.

I understand the program may not be accurate but this is far too much! If I am doing something wrong, please speak up! For now I using Site Class "D" not the recommended "B"

The USGS ground motion tool reports a Site Class of B for an address at: Latitude = 37.87924 and Longitude = -122.29585. This is along SAN PABLO AVE, BERKELEY 94702.

References:

Seismic Hazard Curves and Uniform Hazard Response Spectra using the Earthquake Ground Motion Tool Version 5.0.9a-10/21/2009

I found (Site Class D), Qhaf, Alluvial fan and fluvial deposits (Holocene), Reference: Graymer, R.W., 2000. Geologic map and map data base of the Oakland Metropolitan Area, Alameda, Contra Costa, and San Francisco Counties, California, U.S.  Geological Survey Miscellaneous Field Study Map 2342.

Site Class "D" for this location also is given in: "Mapping NEHRP VS30 Site Classes" figure 1
Thomas L.Holzer, a) M. EERI, Amy C. Padovani, b) Michael J. Bennett, a) Thomas E. Noce, a) and John C. Tinsley, IIIa)

I found a recent soils report on a nearby address that reports a Site Class D.

David Merrick SE




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