[Shake-dev] [Fwd: Re: Solution: regression distances and plotregr?]

[Peggy Hellweg]

Hi Bruce, Pete

your suggestion for fixing it sounds good to me.

Pete, may this help plotregr?

Peggy

-------- Original Message --------
Subject: Re: Solution: regression distances and plotregr?
Date: Wed, 7 Mar 2007 13:05:41 -0700
From: Jack Boatwright <boat at usgs.gov>
To: peggy at seismo.berkeley.edu, Peter Lombard <lombard at seismo.berkeley.edu>

Fine.  NB- it works now.


At 12:03 PM -0800 3/7/07, Peggy Hellweg wrote:
>Hi Jack,
>
>is this an OK way to deal with the "regression distance problem" for
>Small_Seg?
>
>Peggy
>
>-------- Original Message --------
>Subject: Re: regression distances and plotregr
>Date: Wed, 7 Mar 2007 10:47:58 -0800
>From: Bruce Worden <bruce at gps.caltech.edu>
>To: Pete Lombard <lombard at seismo.berkeley.edu>,        Howard G Bundock
><bundock at usgs.gov>
>CC: shake_dev at seismo.berkeley.edu, Peggy Hellweg <peggy at seismo.berkeley.edu>
>References: <17898.2102.936430.691029 at gargle.gargle.HOWL>
>
>Pete/Howard,
>
>I think I can fix Small_Seg to work for PGA and PGV (which means MMI,
>too) without much trouble.  The PSAs are the issue, but since this is
>a regression for small events, you probably don't need those.  For
>any event you wanted to run with -psa, you could use HazusPGV.
>
>Would that work for you?
>
>Bruce
>
>On Mar 3, 2007, at 3:43 PM, Peter Lombard wrote:
>
>> Bruce,
>>
>> I have found a problem in plotregr that I really don't know how to
>> solve. It
>> may also be a problem in grind; you will have to evaluate that!
>>
>> When I wrote plotregr, I intended it to plot the data values so
>> that they
>> could be directly compared with the regression for the event
>> magnitude. That
>> means that the event data should be plotted at the distance that the
>> regression module uses when it computes the regression values.
>>
>> Actual event data shows I have not achieved my goal. In NC, we use the
>> Small_Seg regression, which uses hypocentral distance for PGA and
>> PGV. A
>> recent event here had a hypocentral depth of 16.6 Km. A regression
>> plot
>> (attached) shows one station plotted at less than 4 km distance.
>> That's not
>> what I want.
>>
>> <pga_regr.gif>
>>
>> In plotregr, I try to use the distance function used by the
>> regression, using
>> the following code (borrowed from grind):
>>
>> #---------------------------------------------------------------------
>> --
>>     # Determine which regression to use, load it and create an object
>>     # Get functions for $DIST and $CUSTOM_SITECORR (custom distance
>> and
>>     # site correction functions)
>>
>> #---------------------------------------------------------------------
>> --
>>     my $regress = get_regression($src,$faultcoords);
>>     %amp_sd = $regress->sd();
>>
>>     $DIST = \&dist_rjb;
>>     $CUSTOM_SITECORR = undef;
>>
>>     if (defined $regress->{dist}) {
>> 	print "Using custom distance formula\n";
>> 	$DIST = $regress->{dist};
>>     }
>>
>> The problem is that most regressions don't provide access to the
>> function that
>> is used by the regression to compute distance. Some regression
>> modules use
>> different distance measures for the different PGA, PGV, PSA values.
>> Thus the
>> regressions' distance function needs an argument to specify for which
>> regression variable the distance is to be calculated.
>>
>> For the plotregr program, this leads to misleading plots at near
>> distances.
>>
>> Is this a problem for grind? Does it mean that the "wrong" distance
>> is being
>> used when comparing station data against the regression for the bias
>> computation?
>>
>> Or is am I mistaken in my understanding of how ShakeMap works?
>>
>> Pete
>
>
>--
>
>------------------------------------------------------------------
>Dr. Peggy Hellweg		University of California, Berkeley
>peggy at seismo.berkeley.edu 	Berkeley Seismological Laboratory
>Phone: 510-643-9449		213 McCone Hall # 4760
>Fax:   510-643-5811		Berkeley, CA  94720-4760
>
>There is no problem so great or grave that it cannot be much
>        diminished by a nice cup of tea. -- Bernard-Paul Heroux




-- 

------------------------------------------------------------------
Dr. Peggy Hellweg		University of California, Berkeley
peggy at seismo.berkeley.edu 	Berkeley Seismological Laboratory
Phone: 510-643-9449		213 McCone Hall # 4760
Fax:   510-643-5811		Berkeley, CA  94720-4760

There is no problem so great or grave that it cannot be much
        diminished by a nice cup of tea. -- Bernard-Paul Heroux