infrasound workshop san diego, usa 27-30 october 2003

Infrasound WorkshopSan Diego, USA27-30 October 2003

Infrasound Processing at the IDC using DFX-PMCC

N. BrachetInternational Data CentreWaveform Development Unit

Preparatory Commission for the ComprehensiveNuclear-Test-Ban Treaty OrganizationProvisional Technical SecretariatVienna International CentreP.O. Box 1200, A-1400 Vienna, AustriaE-mail: [email protected]

Infrasound Workshop in San Diego, USA 27-30 October 2003

Outline of the Talk

• Software design and signal review

Started with the increased amount of infrasound data (# IMS stations processed at the IDC)

Understand the signal characteristics with the up-to-date interactive WinPMCC (DASE)

• Software development

Upgrade the existing DFX-PMCC (as delivered in IDC Release 1) using WinPMCC as a reference

• Establish a baseline configuration

Identify key parameters that impact on the DFX-PMCC detection capability

Propose generic DFX-PMCC parameters for processing IMS arrays

• Software testing and validation

Reprocess the known infrasound events archived in the IDC reference database

Large scale testing in a real-time environment


Milestones of DFX-PMCC at the IDC

A few dates:

• June 1998: Installation of DFX-PMCC at the PIDC, Arlington

• April 2001: First IMS station (I26DE) processed at the IDC

• July 2001: Delivery of WinPMCC V1.0.4

• June 2002: DFX-PMCC run offline, results monitored on IDC infrasound intranet

• Summer 2002: IDC analysts test WinPMCC - Validation of the method

• February 2002: Plans for design of future infrasound processing at the IDC

• 2003: DFX-PMCC/WinPMCC comparison - Bug corrections

Major update of DFX-PMCC source code (3D results)

• September 2003: Baseline configuration of DFX-PMCC - validation on reference events

• November 2003 (Plan): DFX-PMCC on development LAN (real-time testing)


DFX-PMCC Software Development

• Major modifications of the structure of the software

Produce and store 3D pixels containing the derived data (az,sp,f,t) into files

Store the results into IDC database using

• The usual DFX tables: ARRIVAL, DETECTION, WFDISC

• additional tables: PMCC_FEATURES, DERVDISC, PMCC_RECIPE

• Enhancements and corrections of existing modules

Improve the azimuth calculation for PMCC families

Use relative speed instead of absolute speed when grouping the pixels (detection of seismic phases)

handle dead channels or met. data in the processing

Improve the module in charge of closing/merging large families

Increase the maintainability: Clean unused source code (10% of total) and comment source code


DFX-PMCC Software Development

• Synchronize DFX-PMCC and WinPMCC results

Bring DFX-PMCC at the same level of confidence as WinPMCC (the reference)

DFX-PMCC

WinPMCC

Azimuth

Speed

Long March rocket launch detected at I34MN, 15 Oct 2003


Baseline Configuration for DFX-PMCC

Key factors impacting on DFX-PMCC detection capability• Preprocessing: DFX Data Quality Control (QC)

• Frequency resolution: Selection of frequency bands and filters

• Azimuth resolution

• Selection of the best sub-network combination

• Control the number of events per station: “size” of signals to be detected

Accomplishments

Air France British Airways

DFX-PMCCin Sep2003

DFX-PMCCin Jan2003

Baseline config.


• Turn off the extended QC and use only a basic QC for gaps, sequences and larger spikes

Results: Close to 100% of bogus HF detections have disappeared

Baseline Configuration for DFX-PMCCDFX-Quality Control (QC)

Action: Reduce DFX-QC action• DFX-QC generates unstable bogus PMCC detections at high frequency• DFX-QC searches and masks poor quality samples - Waveforms are repaired

(interpolation) when possible• Two levels of Data QC: basic (spikes, gaps, sequences) and extended (complex spikes,

multi-channel analysis)

Objective: Remove the HF bogus detections


Objective: Reduce the sensitivity of DFX-PMCC to microbaroms

Preliminary observation: understand the signal characteristics

Microbaroms produced by marine storms

• Narrow band signals ~0.1 - 0.4 Hz

• Series of signal bursts that can be detected over long time periods (typically several hours)

• More variation in detection azimuths when the source is closer to the station

Baseline Configuration for DFX-PMCCDFX-Quality Control


Action: Use lower weight in the processing of specific freq. bands• Do not use a band-stop filters

• Take advantage of the PMCC method for clustering pixels into detection families

• Detection pixels are those which verify the consistency relation

• Pixels with similar attributes (az,sp,f,t) are grouped into families

• Families are turned into detections if they contain a minimum number of pixels

time

Fre

quen

cy b

and

PMCC Pixel (az,sp,f,t)

time

Fre

quen

cy b

and

PMCC Family avg(az,sp,f,t)

Microbaroms detection

[0.1-0.4]

Baseline Configuration for DFX-PMCCFrequency Bands


Results:• “Trap” the microbaroms detections in a narrow frequency band.

Post-processing can be applied in order to identify these detections and not to use them in subsequent stages of processing (event building)

• Remove the smallest sequences of microbaroms

Baseline Configuration for DFX-PMCCFrequency Bands

• Same logic can be applied to any narrow band signal

3 families of pixels = 3 detections

Isolated pixelswith similar characteristics

(microbaroms)-> No detection

Isolated pixelswith different characteristics

-> No detection[0.1-0.4]

Families, az

Families, sp

Pixels, az

Pixels, sp

I26DE, 12 Jan 2003


Objective: Improve the frequency resolution of the signal detected Signals like microbaroms are detected by DFX-PMCC at frequencies up to 1Hz

Action: Use a band-pass filter that has a steep roll off

Results:• Slightly decreases the detection capability but substantially improves the frequency resolution

• The microbaroms detected by DFX-PMCC are more constrained to lower frequencies <0.5Hz

Baseline Configuration for DFX-PMCCFrequency Resolution

Chebychev [0.1-0.3], order 2 Chebychev [0.1-0.3], order 3


Examples of microbaroms detected at I07AU (6 Sep2003)

Source: FNMOC Wave Watch 3 (WW3)

Baseline Configuration for DFX-PMCCFrequency Resolution

DFX-PMCC, Chebychev order 2

DFX-PMCC, Chebychev order 3 (Steeper roll-off)

I07AU


Objective: Improve the azimuth resolution• Trigger detections on signals with stable characteristics, focus on azimuth stability

• Prepare for a basic event categorization

Action:• Use a low threshold in azimuth when forming the PMCC families (+/- 6 or 10 degrees)

• Find a good compromise between a good azimuth resolution and high number of detections produced (split families). Risk of merging independent families if the azimuth criterion is too loose.

Azimuth threshold

Split families

“Event” categorization

Azimuth accuracyMissed small detections

(Total # of detections)

Unstable detections

Baseline Configuration for DFX-PMCCAzimuth Resolution


Results: Example of microbaroms at I07AU (6 Sep 2003)

Parameter:az = +/- 6 deg

Output:89 detectionsbackaz = 224.7 +/- 5.4

Baseline Configuration for DFX-PMCCAzimuth Resolution

Parameter:az = +/- 10 deg

Output:55 detectionsbackaz = 225.5 +/- 7.7


Objective: • Study how the selection of array geometry impacts on the detection capability

• Results presented at the IMS infrasound meeting in Vienna, March 2003

Action:

For identified signals (Concorde, microbaroms) check the detections when removing one array element from the processing

Results:

• Good detection capability and quality of PMCC even with low number of array elements (4)

• Good detection capability of small aperture arrays well complemented by quality of detection features provided by large aperture arrays

• The central element plays a key role in the PMCC detection processing

• DFX-PMCC shall configuration includes a large number of combinations of sub-networks

Plan: intelligent selection of sub-networks based on data channel QC (Future evolution)

Baseline Configuration for DFX-PMCCArray Geometry


Example: I34MN 18 Jan 2003 microbaroms between 8:00-12:00 GMT

Baseline Configuration for DFX-PMCCArray Geometry

I34H1Az 80

Az 320 Az 80Az

Sp

Az

Sp

Az

Sp

Az

Sp

Az

Sp

-H1

-H2

-H3

-H4

All


Objective: Set the minimum “size of events” to be detected

• DFX-PMCC does not work with amplitudes (no minimum SNR threshold applied)

• The “size” of the signal to be detected depends on the minimum number of pixels per family

• It is the last parameter to be tuned according to the types of events detected at the station

time

Fre

quen

cy b

and

PMCC Pixel (az,sp,f,t)

time

Fre

quen

cy b

and

PMCC Family avg(az,sp,f,t)

Family would not be built if min. number of pixels<5

Baseline Configuration for DFX-PMCCDetection Threshold


• Example: Argyle mine at I07AU, ML2.4 730km (16Apr2002)

Baseline Configuration for DFX-PMCCDetection Threshold

Pixel threshold=15 -> 13 detections

SNR=9.8

Pixel threshold=100 -> 1 detection

Families

Pixels

Families

Pixels


DFX-PMCC testing and validation

Test the baseline configuration of DFX-PMCC on the 30 IDC infra. ref. events 2001 SEL3 DFX-PMCCDay Event description IMS array Seismic Infra Seismic Infra23 Apr North Pacific bolide I10CA

I26DE I59US

23 Jun Peru main earthquake I08BO

23 Jun Peru aftershock I08BO 7 Jul Peru earthquake I08BO 15 July Etna eruption I26DE 21 Sep Toulouse explosion I26DE 14 Oct Canada bolide I10CA (!) 21 Oct Nuremberg explosion I26DE

14 Nov China earthquake I34MN

18 Nov Leonid meteorite I59US

200226 Jan US missile test I59US 9 Mar Central Pacific bolide I10CA (!)

I57US I59US

12 Mar Space Shuttle STS109 I10CA (!) 6 Apr Germany bolide I26DE

Good quality detection

Poor quality detection

No detection

Not available


DFX-PMCC testing and validation

Test the baseline configuration of DFX-PMCC on the 30 IDC infra. ref. events

2002 (Cont.) SEL3 DFX-PMCCDay Event description IMS array Seismic Infra Seismic Infra16 Apr Argyle mine I07AU 6 Jun Mediterranean sea bolide I26DE 8 Sep New Guinea earthquake I07AU

28 Sep Watusi explosion I10CA (cor.) 28 Sep Indonesia earthquake I07AU 23 Oct Alaska earthquake I10CA (cor.) 3 Nov Alaska earthquake I10CA (cor.)

20031 Feb Space Shuttle STS107 I10CA (cor.) 1 Feb Concorde I26DE 27 Mar Explosion Billy-Berclau I26DE 8 Jun Soyuz rocket launch I31KZ 12 Aug Soyuz rocket launch I31KZ 14 Aug Greece earthquake I26DE 27 Aug Hawaii earthquake I59US 29 Aug Soyuz rocket launch I31KZ 15 Oct LongMarch rocket launch I34MN

Good quality detection

Poor quality detection

No detection

Not available


Summary• History of DFX-PMCC connected to

• The amount of infrasound data processed at the IDC (# of IMS stations)

• Large contribution of WinPMCC (new vision for presenting the derived results)

• DFX-PMCC provides a powerful automatic detector for infrasound signals with

• Good detection capability and feature extraction quality

• Large variety of signals detected

• Low level of false alarms

• DFX-PMCC brings reliability into IDC infrasound processing

• Since September 2003, Maturity of the software and high level of confidence

• The baseline configuration has been successfully tested on the IDC reference events

• Plans for the near future

• Large scale testing in a real-time environment is to be initiated (November 2003)

• Limit the impact of long duration signals on the automatic processing

• Develop in parallel the future interactive infrasound software at the IDC

infrasound workshop san diego, usa 27-30 october 2003

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