power spectral density (psd) probability density functions (pdf)

Power Spectral Density (PSD)Probability Density Functions (PDF)

A Seismic Data QC and Network Design Tool

Developers:Dan McNamara, Ray Buland @ ANSS NOCRichard Boaz @ Boaz Consultancy (formerly IRIS PASSCAL)

Others involved:Harold Bolton, Jerry Mayer @ ANSS IDCCTim Ahern , Bruce Weertman @ IRIS DMC

USGS-IRIS Collaborative QC Development Effort

USGS noise PDF algorithm - Summer 2001USGS informal QC PDF - Fall 2001 IRIS DMC Quack RFP - Fall 2002Proposal funded - Spring 2003Programmer hired - Fall 2003DMC QUACK PDF operational - June 2004BSSA Paper published - Aug. 2004USGS Formal QC PDF - Sept. 2004Stand Alone PDF - Oct. 2004

Phase II Development - FY 2005-2006QDAT:database PSDsanalyst GUI

ANSS NOC IDCChttp://gldqc/cgi-bin/pdf (ANSS backbone, internal USGS)IRIS DMC (IU, II, UW, NM most global and US regional networks)http://www.iris.washington.edu/servlet/quackquery/IRIS PASSCAL Earthscope USarray

http://www.iris.washington.edu/servlet/quackquery_us/Berkeley Seismic Lab

http://moho.geo.berkeley.edu/seismo/PDF/University Utah Seismogram NetworkORFEUS Taiwan National Seismograph Network

PDF Methods and Explanation websitehttp://geohazards.cr.usgs.gov/staffweb/mcnamara/PDFweb/Noise_PDFs.html/

PDF Locations

http://gldqc/cgi-bin/pdf



http://www.iris.washington.edu/servlet/quackquery/







http://www.iris.washington.edu/servlet/quackquery_us/

http://moho.geo.berkeley.edu/seismo



http://geohazards.cr.usgs.gov/staffweb/mcnamara/PDFweb/Noise_PDFs.html/

http://geohazards.cr.usgs.gov/staffweb/mcnamara/PDFweb/Noise_PDFs.html/

Method: Power Spectral Density Probability Density FunctionsRaw waveforms continuously extracted from waveserverIn 1 hour segments, overlapping by 50%.PSD pre-processing:

trend and mean removal10% cos taper applied

No screening for earthquakes, or transients and instrumental glitches such as data gaps, clipping, spikes, mass re-centers or calibration pulses

PSD calculated for each 1 hour segmentWith ASL algorithm for direct comparison to NLNM.

PSD is smoothed by averaging powers overfull octaves in 1/8 octave intervals.Points reduced from 16,385 to 93.

Center points of octave averages shown.

Power Frequency Distribution HistogramsPSDs are accumulated in 1dB power bins from -200 to -50dB.

Distributions are generated for each period in 1/8 octave period intervals.

Histograms vary significantly by period.

- 1s has strong peak and a narrow range of powers.

- bimodal distributions at 10, 100s

-All have sharp low-power floor with higher power tails

Next step:Convert histograms to Probability Density Functions

Individual histograms for each period are converted to PDFs by normalizing each power bin by total number of observations.

Total distribution of powers plotted.Not simply minimum powers.

PSD Probability Density Function for ISCO BHZ

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.



HLID - automobile traffic along a dirt road only 20 meters from station HLID creates a 20-30dB increase in power at about 0.1 sec period (10Hz). This type of cultural noise is observable in the PDFs as a region of low probability at high frequencies (1-10Hz, 0.1-1s).

Body waves occur as low probabily signal in the 1sec range while surface waves are generally higher power at longer periods.

Automatic mass re-centering and calibration pulses show up as low probability occurrences in the PDF.

Artifacts in the Noise Field

Current Noise PDF Uses

Network SOH monitoringDead stationDetection ModelingDesign Planning

Station Quality Site quality Current stationsfuture backboneANSS Rankings

Noise Researchsourceshurricanesambient noise model

Hailey, ID 08/2001-05/2002

McNamara and Buland (2004) BSSA

Realistic view of noise conditions at a station. Not simply lowest levels experienced.





GOTO:IRIS DMChttp://www.iris.washington.edu/servlet/quackquery/

Earthscope USarrayhttp://www.iris.washington.edu/servlet/quackquery_us/


http://www.iris.washington.edu/servlet/quackquery_us/

Lightning strike hours after Station began operation









Brune minimum Mw Mw

Regional Network Simulation6 stations from NM regional network with well established noise baselines.

Detection threshold lowered in New Madrid region by 0.1-0.3 unitswith addition of NM network.

Regional Station Limitations:- high noise in Cultural noise band (1-10Hz)- PVMO instrumented with Guralp CMG-3esp seismometer (50Hz) and Quanterra Q-380 digitizer at 20sps. Power rolloff at Nyquist~10Hz.

PVMO

Mw

Backbone Stations on Satellite GR4

Backbone stations on Satellite SM5

Detection Maps Used for Prioritization of Maintenance Issues

Mw

ANSS backbone distributed over 2 satellites to protect against total network outage. Simulations demonstrate detection in the event of a satellite failure.

Maintenance decisions could be made based on real-time changes in detection thresholds.

GR4 expected to die within 3 years.


are needed to see this picture.QuickTime™ and a

TIFF (Uncompressed) decompressorare needed to see this picture.

3km from train 20km from train





Meremonte, M., D. McNamara, A. Leeds, D. Overturf, J. McMillian, and J. Allen, ANSS backbone station installation and site characterization, EOS Trans. AGU, 85(47), 2004.



Station Quality Site quality Current stationfuture backboneANSS Rankings


GSN Standing Committee Report:

An Assessment of Seismic Noise Characteristics for the ANSS Backbone

and Selected Regional Broadband Stations

By D. McNamara, Harley M. Benz and W. Leith

Also

McNamara, D.E., H.M. Benz and W. Leith, USGS Open-File Report, in press, 2005.



Station Quality Site quality Current stationfuture backboneANSS Rankings

Noise Researchsourceshurricanesambient noise models

McNamara, D.E., R.P. Buland, R.I. Boaz, B. Weertman, and T. Ahern, Ambient seismic noise, Seis. Res. Lett., in press, 2005.

Plans for future development: QDATDatabase hourly PSDs to allow:

creative selection of data for PDF generationPlayback as a movie (i.e. graphic equalizer)Additional types of visualizations

Regional noise trends diurnal and seasonal variations

Researchnoise sourcesbaselinesauto ID of problem artifacts

Operationsvault designtelemetry performanceautomated problem reporting and notification



Hurricanes



Seismometer casing differential motion



Regional noise trends diurnal and seasonal variationsspectograms





Regional Noise Characteristics

6am local time

Noise across all periods increases 10-15dB during the working daywith the exception of the microseism band (~7-8s).

Constructed from 90th percentilecomputed from PDFs binned foreach hour of theday.

Data from Sept 2001 toOct 2004

Short period noise increases during the summer months.Microseism band (~7-8s) noise increases during the fall and winter.

Constructed from 90th percentilecomputed from PDFs binned foreach month of the year.

Data from Sept 2001 toOct 2004

School begins

Noise Baselines: Which Statistic?Mode, Average or Median

power spectral density (psd) probability density functions (pdf)

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