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Development of Automated Signal and Meta-dataQuality Assessment at the USGS

Advanced National Seismic System (ANSS)National Earthquake Information Center (NEIC)

D.E. McNamara, R. Buland, R. Boaz, H. Benz, L. Gee, W. Leith

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Broadband Stations Used by the NEIC~4,000 real-time channels~4,000 real-time channels

~450 stations~450 stationsANSS

IW

IMS

CDSN

GTSN

SLU

GSN

SNL

Weston

BILIKIN

LLNL

ATWC

PTWC

AVO

NMT

GEOSCOPE

PRSN

CISNUNR

LDEO

AEIC

CERI

MEDNET

GEOFON

Need auto QC methods for contributedNeed auto QC methods for contributed

stations to improve NEIC productsstations to improve NEIC products

Instrument Responses

IRIS DMC

Currently manual inspection methods are used to assurequality of GSN and ANSS backbone data and meta-data.

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NEIC Auto QC: Continuous Noise MonitoringProbability Density Function

Instrument Response

Gain, poles, zeros

calibration

Telemetry Issues

Gaps, drop-outs, dead channel System Transients

Mass recenters, spikes, clips

Vault performance

Pad tilt

Diurnal/seasonal variations

Cultural Noise Sources

Local machinery

Roads

ships

Network capability modeling

Detection threshold

Detection time

location error

14 day Probability Density Function constructed

with 672 individual PSDs, in 1/8 octave period and

1dB bins.

PDF Advantages:

earthquakes

Telemetry gaps

Canal LPnoise

microseism

Human activity

Barro Colorado, Panama (BCIP BHZ)

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PDF MethodData Prep:

1-hour time segments continuously

extracted from NEIC CWB, overlapping

by 50% (30 min.).

trend and mean removal

10% cos taper applied

No screening for earthquakes, or

transients and instrumental glitches such

as data gaps, clipping, spikes, mass re-

centers or calibration pulses

McNamara, D. E. and R.P. Buland, Ambient Noise Levels in the ContinentalUnited States, Bull. Seism. Soc. Am., 94, 4, 1517-1527, 2004.

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PSD calculatedfor each 1 hoursegmentWith ASLalgorithm for

direct comparisonto LNM.

PSD is smoothedby averagingpowers overfull octaves in1/8 octaveintervals.

Center points ofaverages shown.

LNM and HNM: Peterson (1993)

PDF Method: 1 hour

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PDF Method: 2 hours

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PDF Method: 1 day, 48 hours

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PDF Method: 1 week, 336 hours

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PDF Method: 2 weeks, 672hours

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Count PSD intersections per bin and normalize by total number of PSDs.

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14 day Probability Density Function constructed with 672 individual

PSDs, in 1/8 octave period and 1dB bins.

earthquakes

Telemetry gaps

Canal LPnoise

microseismHuman activity

Barro Colorado, Panama (BCIP BHZ)

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Boaz Consulting

IRIS - Data Management Center, Seattle, WA

IRIS - PASSCAL Instrument Center, Socorro, NM

National Science Foundation, Washington, D.C.United States Geological Survey - Golden, CO

PQLX

compute PDFs

build PSD database

graphically investigatetime series and PDFs

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NEIC Auto-QC: Detects matches and outliers

Reference models

Petersen High and Low Noise Models

- define standard operating range

Station Specific Noise Models- define station noise conditions

Noise Source Models- define station specific transients

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Petersen High and Low Noise ModelsHNM - defined by noisey GSN island stationsLNM - defined by quiet GSN continental stations

Tegucigalpa, Honduras, CU TEIG

Peterson, Observation and modeling of seismic background noise,U.S. Geol. Surv. Tech. Rept., 93-322, 1-95, 1993

P-waves Surface wavesSurface waves

BHZ LHZ

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Station Models - 10th and 90th percentiles of PDF distribution- define station ambient noise conditions

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Station Model Examples

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Bad Units input units

Displacement Instead of Velocity

Missing zero in Response File

Results in CW rotated PSD: High Amps at Low Period Low Amps at High Period

Corrected Response

PDF Instrument Response Sensitivity

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Bad STS2 Gain

Used 20,000 Volts/(m/s)Instead of 1500 Volts/(m/s)

Resulting in low correctedPower across spectrum.

Corrected Response

PDF Instrument Response Sensitivity

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60 day PDF US LRAL BHZ

STS2 auto re-center

seconds

Time series

Noise Source Modelsuse PQLX software to define station

specific transients and noise conditions

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60 day PDF US MSO BHZ

Calibration pulse

seconds

Time series

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60 day PDF AK MCK BHZ

Short data gaps

seconds

Time series

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Large Gaps

On-stops

Cultural noiseDiurnal Variations

Surface waves

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Detector Example: CU BCIP BHZ

1 hour PSD

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PSD fits within station model and HNM, LNM

match if 75% fit

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1 hour PSD

No match if

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1 hour PSD

calibration

No match if

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1 hour PSD

Large gaps No match if

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1 hour PSD

Small gaps

No match if

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1 hour PSDSTS2 re-center

match if 75% fit

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1 hour PSDSmall gaps

match if 75% fit

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1 hour PSD

Small gaps

No match if

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In Summary

Auto-QC semi-operational at USGS NEIC- building DB of continuous hourly PSDs- daily inspection of PDFs with PQLX- daily computation of total station models- hand defined many noise models with

PQLX - daily stats on PSD matches and outliers

Further Development- additional noise sources from outliers- fine tune sensitivity parameters- PQLX enhancements- publish PDFs and stats to WWW

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Multi-Platform: Linux, MAC OS, Solaris

Source code for PQLX is freely available for download via WWW from:(source code managed using SVN)

http://wush net/svn/PQLX/tars

username = PQLXtars

password = getPQLX

Publicly Available, and Fully Searchable, Website for BugReporting and Enhancement Requests:

http://wush net/bugzilla/PQLX

PQLX Software

McNamara S32A 06

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