NGA Attenuation - Abrahamson & Silva

[moe333]

Hi all,

I am trying to estimate the +1 std. deviation of PGA for a M6.9, Vs=800 m/s (estimated), reverse fault (dip=75 degrees) at Rrup=2km (Rjb=0). The site is on the hanging wall of the fault. I am coming up with PGA=1.46g for these parameters using the new NGA attenuation relationship from Abrahamson & Silva, and this is about the same value as I have calculated using their 1997 relationship. These values are significantly higher than other NGA authors predictions.

One reason I am asking is the NGA relationships were supposedly predciting lower ground motion than the 1997 realtionships. If my calculations are correct, I'm wondering if this may be due to larger uncertainty for the +1 std. deviation value than with previous relationships?

If anyone has this relationship programmed I'd be interested to know what value they come up with for these parameters.

Thanks

 

[BigH]

moe333 - don't want you to think that I am ignoring your post - I just don't have the experience in the particular matter you asked. Hoping that David will respond . . .

 

[moe333]

Thanks BigH, I know it's a fairly specific and obscure topic, but was hoping someone had coded these new relations in. The standard deviation equations in particular are pretty involved and easy to make a mistake.

 

[BigH]

Do you have the references? A few years ago, Canada redid their entire seismic stuff . . . email? I can forward some of it to you in case it might prove useful in some manner.

 

[moe333]

Thanks, but I have the reference for the Abrahamson & Silva (2008) relation as well as the Canadian documents. Just trying to get an independent check on my numbers.