zackspica / iris-hvsr Goto Github PK

Incorporated Research Institutions for Seismology (IRIS)

Data Management Center (DMC)

Data Products Team

horizontal to vertical spectral ratio (HVSR)

2018-07-10

DESCRIPTION:

The horizontal to vertical spectral ratio (HVSR) of ambient noise provides information on the fundamental natural frequency of the local sediments when there is a large acoustic impedance contrast between sediments and underlying rocks.

This IRIS DMC Python script bundle provides tools to compute and plot horizontal to vertical spectral ratio (HVSR) curves using IRIS DMC's MUSTANG PDF-PSD web services. The bundle contains 2 Python scripts:

• computeStationChannelBaseline.py is a Python script that uses IRIS DMC's MUSTANG noise-pdf (http://service.iris.edu/mustang/) web service to compute channel-specific noise-baseline for a given station (McNamara et al., 2009). The resulting baseline represents the long-term PSD PDF characteristics of the station-channel pair in the form of median, lower and higher percentiles of the available PSDs for the station.

• computeHVSR.py - is a Python script that uses IRIS DMC's MUSTANG noise-psd/pdf web services (http://service.iris.edu/mustang/) to compute horizontal-to-vertical spectral ratio (HVSR) for a given station with the following options:

  • Remove PSDs that fall outside the station noise baseline as computed by computeStationChannelBaseline.py above (parameter: removeoutliers=0|1).

  • Compute HVSR using one of the methods below (parameter: method=1|2|3|4|5|6).

  • Output a peak rank report with ranking based on SESAME 2004 (not avaiable for DFA method)

  • The HVSR computational methods supported:

    (1) DFA, Diffuse Field Assumption method (Sánchez-Sesma et al., 2011)

       NOTE: The MUSTANG noise-psd web service Power Spectral Density estimate for seismic channels are computed using the algorithm outlined here 
             (http://service.iris.edu/mustang/noise-psd/docs/1/help/). This algorithm involves averaging and normalization that may result in 
             smoothing of some of the peaks that may otherwise be observed by direct computation of FFT and DFA. With this smoothing, the DFA 
             results tend to be closer to the vector summation method, method (4) below.
    

    (2) arithmetic mean, H ≡ (HN + HE)/2

    (3) geometric mean, H ≡ √HN · HE

    (4) vector summation, H ≡ √H2 N + H2 E

    (5) quadratic mean, H ≡ √(H2 N + H2 E )/2

    (6) maximum horizontal value, H ≡ max {HN, HE}

        NOTE: combining the two horizontal components using one of the above methods is reviewed by Albarello and Lunedei (2013).
    

CHANGES.txt
   - a text file containing the history of changes to this bundle

INSTALL.txt
   - installation notes

README.md
   - this file

bin/
   - scripts directory containing:
        + computeStationChannelBaseline.py (described above)
        + computeHVSR.py (described above)

param/
   - parameters directory containing:
        + getStationChannelBaseline_param.py - the configuration parameter file for the computeStationChannelBaseline.py script above
        + computeHVSR_param.py - the configuration parameter file for the computeHVSR.py script above

lib/
   - bundle library files:
        + fileLib.py - a collection of functions to work with files and directories
        + msgLib.py - a collection of functions to print messages

INSTALLATION:

see the INSTALL.txt file

USAGE:

bin/computeStationChannelBaseline.py

   Call the script and provide the run arguments. By defining a parameter on the command line, user overrides the values defined for that parameter in the parameter file. 
   
   The call should have the form:

         getStationChannelBaseline.py net=netName sta=staName loc=locCode {chan=chanCode} start=2007-03-19 end=2008-10-28 {plot=[0,1] verbose=[0,1] percentlow=[10] percenthigh=[90] xtype=[period,frequency]}
     
         Note: the default values for the parameters between {} may be provided in the parameter file

bin/computeHVSR.py

   Call the script and provide the run arguments. By defining a parameter on the command line, user overrides the values defined for that parameter in the parameter file.
   
   The call should have the form:

computeHVSR.py net=TA sta=TCOL loc= chan=BHZ,BHN,BHE start=2013-01-01 end=2013-01-01 plot=1 plotbad=0 plotpsd=0 plotpdf=1 verbose=1 ymax=5 xtype=frequency n=1 removeoutliers=1 method=4

net=network

sta=station

loc=location code

chan=channel code

start=start date

end=end date

plot=[0,1]

plotbad=plot

rejected PSDs

plotpsd=plot PSDs

plotpdf=plotPDF

verbose=verbose mode

ymax=plot Y-axis maximum

xtype=x-axis type [frequency,period]

n=break Start-end interval Into "n" segments

removeoutliers=remove PSDs that fall outside the station noise baseline

method=HVSR computational method (see below)

         Note: any parameter given on the command line will override the one defined in the parameter file

EXAMPLES:

         bin/getStationChannelBaseline.py net=IU sta=ANMO loc=00 chan=BHZ,BH1,BH2 start=2002-11-19 end=2008-11-13 plot=1 verbose=0 percentlow=10 percenthigh=90
         bin/getStationChannelBaseline.py net=IU sta=ANMO loc=00 start=2002-11-19 end=2008-11-13 plot=1
         bin/getStationChannelBaseline.py net=IU sta=ANMO loc=00 chan=BH1 start=2002-11-19 end=2008-11-13 plot=1

         bin/computeHVSR.py net=IU sta=ANMO loc=00 chan=BHZ,BH1,BH2 start=2007-05-01 end=2007-06-01 plot=1 verbose=1 ylim=5 removeoutliers=1 method=4
         bin/computeHVSR.py net=UW sta=RATT loc= chan=BHZ,BHN,BHE start=2014-01-01 end=2017-01-01 plot=1 plotbad=0 plotpsd=0 plotpdf=1 verbose=0 ylim=5 xtype=frequency n=20 removeoutliers=0 method=4

REFERENCES:

Albarello, Dario & Lunedei, Enrico. (2013). Combining horizontal ambient vibration components for H/V spectral ratio estimates. Geophysical Journal International. 194. 936-951. 10.1093/gji/ggt130.

McNamara D.E., C.R. Hutt, L.S. Gee, H.M. Benz, and R.P. Buland, 2009, A method to establish seismic noise baselines for automated station assessment, Seismological Research Letters Jul 2009, 80 (4) 628-637; DOI: 10.1785/gssrl.80.4.628. http://srl.geoscienceworld.org/content/gssrl/80/4/628.full.pdf

Francisco J Sánchez-Sesma, Francisco & Rodriguez, Miguel & Iturraran-Viveros, Ursula & Luzón, Francisco & Campillo, Michel & Margerin, Ludovic & García-Jerez, Antonio & Suarez, Martha & Santoyo, Miguel & Rodríguez-Castellanos, A. (2011). A theory for microtremor H/V spectral ratio: Application for a layered medium. Geophysical Journal International. 186. 221-225. 10.1111/j.1365-246X.2011.05064.x.

Guidelines for the Implementation of the H/V Spectral Ratio Technique on Ambient Vibrations, December 2004 SESAME European research project WP12 – Deliverable D23.12, European Commission – Research General Directorate Project No. EVG1-CT-2000-00026 SESAME. ftp://ftp.geo.uib.no/pub/seismo/SOFTWARE/SESAME/USER-GUIDELINES/SESAME-HV-User-Guidelines.pdf

HISTORY:

- 2018-07-10: prerelease R.2018191

- 2017-11-28: computeHVSR R.2017332

- 2017-11-16: initial version R.2017320

COMMENTS/QUESTIONS:

Please contact [email protected]