[Shake-dev] intensity bias in ShakeMap v3.5

[Georgia Cua]

Hi Bruce,

Thanks for your quick response. We'll do an update and let you know how it goes.

Thanks again,
Georgia

On Jan 18, 2011, at 10:41 PM, Bruce Worden wrote:

> Hi Georgia,
> 
> There was a bug in Wald99 (and AK07) where the intensities returned were allowed to exceed the 1 to 10 range. Oddly, the limiting code was in there, but commented out -- no doubt an error on my part. Fixing these bugs (and a minor unrelated bug in grind) now produces the expected result: if all of your intensities are 1, your bias will be zero.
> 
> It is important to use converted PGM in the intensity bias because not all maps have observed intensity, and without some data we can't do the bias. Doing the bias results in a significant reduction in the error of the map. I've tested this extensively both with and without observed intensities. In cases where you do have observed intensities, those are weighted higher than the converted PGMs in the bias calculation.
> 
> You can get the updated code with 'svn update' and 'make'. Let me know how it goes.
> 
> Bruce
> 
> 
> On Jan 18, 2011, at 3:19 AM, Georgia Cua wrote:
> 
>> Dear Bruce, shake-dev,
>> 
>> I have been working on our ShakeMap v3.5 installation in Switzerland.
>> 
>> I noticed something peculiar with the behaviour of the intensity bias.
>> 
>> I have the observed PGA and PGV from a M3.3 in Switzerland. (To be safe, I used Small as the GMPE and Wald99 as the GMICE. The behaviour is similar when I use our Swiss-specific GMPE and GMICE.)
>> 
>> When I run this event with the observed PGM as input, there are large bias values for PGA and PGV, -1.5 and -0.7. (Those are expected, as PGA and PGV in Switzerland tend to be lower for a given magnitude than predicted by California relationships.) What troubles me is that the intensity magnitude bias turns out positive (1.43).
>> 
>> If I run a shakemap for this event without the PGM as input (just providing the event.xml file), the maximum intensity is 3.64. When I run it with the PGM as input, the maximum intensity is 5.1, even though the PGA and PGV biases are both negative.
>> 
>> I've run this same event on our v3.2 installation, and there, it seems to behave as I expect, where if the PGA and PGV biases are negative, the maximum intensity using the PGM observations will be lower than when running it without the observations.
>> 
>> I am attaching the message logs from running shake, grind.conf, the info.xml file, as well as the regression plots.
>> 
>> I am not sure where I am going wrong. Thanks in advance for your help.
>> 
>> Georgia
>> 
>> PS. When there is no native intensity data provided as input, and no IPE is specified, should the intensity bias still calculated?
>> 
>> <test33.with_pgm.shake.log><ATT00001.html><grind.conf><ATT00002.html><with_pgm.info.xml><ATT00003.html><with_pgm.pga_regr.png><ATT00004.html><with_pgm.pgv_regr.png><ATT00005.html><with_pgm.mi_regr.png><ATT00006.html>
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> 



-----------------------------
Dr. Georgia Cua
Swiss Seismological Service
Institute of Geophysics
ETH Zurich, NO H61
Sonneggstr 5
CH-8092 Zurich
Switzerland

Tel:  +41-44-633-7574   
Fax: +41-44-633-1065   

georgia.cua at sed.ethz.ch
-----------------------------



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