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