A New QUACK Controlet: Sesimic Noise Probability Density ...

A New QUACK Controlet: Sesimic Noise Probability Density Functions

Developers:

Dan McNamara, Ray Buland, Harold Bolton, Jerry Mayer @ USGS

Richard Boaz @ Boaz Consultancy (formerly IRIS PASSCAL)

Tim Ahern , Bruce Weertman @ IRIS DMC

IRIS-USGS Collaborative QC Development EffortUSGS noise PDF algorithm - Summer 2001

USGS informal QC PDF - Fall 2001

IRIS DMC Quack RFP - Fall 2002

Proposal funded - Spring 2003

Programmer hired - Fall 2003

DMC QUACK PDF operational - June 2004

BSSA Paper published - Aug. 2004

USGS Formal QC PDF - Sept. 2004

Stand Alone PDF - Oct. 2004

PDFs at IRIS DMC QUACK interfacehttp://www.iris.washington.edu/servlet/quackquery/

USarray datahttp://www.iris.washington.edu/servlet/quackquery_us/

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

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

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

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

Method: Power Spectral Density Probability Density Functions

Raw 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 Histograms

PSDs 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.-some periods (1s) have strong peak and a narrow range of powers.-others have double peaks (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 and combined into one color plot.

Probability Density Function for ISCO BHZ

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Establish noise baselines using mode.

ANSS Seismic Noise Monitoring• Establish ANSS station noise baselines• Select ANSS backbone instrumentation• ANSS backbone site criteria• Network detection thresholds• Station maintenance issues

– System transients– Prioritize repairs– Automate problem notification

• Cultural noise source modeling• Microseism modeling

MotivationHailey, ID 08/2001-05/2002

All data is included, no pre-screening for quakes, data gaps, glitches, high noise data.

2370 individual PSDs, binned in 1/8 octave intervals, are used to construct a Seismic Noise Probability Density Function for HLID BHZ.

McNamara and Buland (2004) BSSA

Cars Local QuakesTeleseismsApproach

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



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 monitoringInstrument responseDead station

Detection ModelingStation Quality

Current stationsfuture backboneANSS Rankings

Noise Researchsourceshurricanesambient noise model

Lightning strike hours after field crew left site


Network monitoringStation QualityInstrument responseDead station




Brune minimum Mw, 80% noise threshold 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.

Hughes states.“There will be a seamless transition to a new satellite…”




Network monitoringInstrument responseDead station






3km from train 20km from train

Plans for future developmentDatabase 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 sourcesauto ID of problem artifacts

Operationsvault designtelemetry performanceautomated problem reporting and notification



Hurricanes



sts2 automatic mass re-centers





Operationsvault designtelemetry performanceautomated problem reporting and notification



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.

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.

School begins





Operationsvault design and station sitingtelemetry performanceautomated problem reporting/notification

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

http://geohazards.cr.usgs.gov/staffweb/mcnamara/Share/ANSS_rankings.doc

PDFs at IRIS DMC QUACK interfacehttp://www.iris.washington.edu/servlet/quackquery/

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

A New QUACK Controlet: Sesimic Noise Probability Density ...

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