Infrasound Technology Workshop Tokyo, Japan November 2007

Infrasound Technology WorkshopTokyo, JapanNovember 2007

Smooth Introduction of Infrasound Data into the IDC Reviewed Event BulletinPart I: Procedure and Recent Developments

Nicolas Brachet1, Abdou Salam Ndiath2, Misrak Fisseha2, Ali Kasmi2, Mehves Feyza Ocal2, Kirill Sitnikov2, Gadi Turyomurugyendo2 and John Coyne1

International Data Centre 1Software Applications Section2Monitoring and Data Analysis Section

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

Infrasound Technology Workshop in Tokyo, Japan November 2007 Page 2

Outline

Smooth introduction of infrasound into IDC operations- Development of new interactive tools for infrasound data

- Preliminary Procedure & Guidelines for saving infrasound events

- Increase the visibility of IDC infra results inside and outside the PTS

Enhancement of the Automatic Processing- Modify the detection code (low frequency)

- Refine the categorization and phase association criteria

- Challenging R&D in atmospheric modeling


Current Use of Infrasound Data in Operations

SEL3 events (SHI)

Testbed

Detection &Categorization

Phase associationTT tables 318m/s

1 Operations

LEB Events (SH)

2

Phase associationTT tables 318m/s

SEL3 events (SH)


RoutineLead Analyst

Review

REB events (SHI)

RoutineAnalyst Review

RequestedAnalyst Review

LEB Events (SHI)

External sourcesNews, volcano/meteorite alertsPersonal comm.

Infrasound prediction

Infraref database

GoogleEarth

Wiki Report

Testing

/ validation

Atmosph. modeling

(G2S-ECMWF)

Phase associationTT tables 300m/s+ Freq attenuation

Development Area3

+ Low frequency

SEL3 events (SHI)


Infrasound Analyst Review


Preliminary Procedure for saving infra events

• No infrasound specific procedure and guidelines in PIDC/IDC documentation

• Preliminary procedure proposed in 2007 in collaboration with the group of

infrasound specialized analysts

General rules for building REB events

1. Event Definition Criteria (EDC): Confirmation is based on a weighted-count of defining observations (arrival time, azimuth, and slowness). The minimum sum of the weights of the defining phase observations must be 4.6 for REB events.

2. REB event must include defining observations on at least 3 primary stations.


Event Definition Criteria

Station Type Phase Type Time

weight

Azimuth weight

Slowness weight

EDC weight

Seismic Array P, Pn, Pg, PKP, PKPab, PKPbc, PKiKP 1 0.4 0.4 1.8

Seismic Array pP, sP, pPKP, pPKPbc, PcP, ScP, SKP, SKPbc PP 0.4 0 0 0.4

Seismic Array Sn, Lg 0.7 0.4 0.4 1.5

Seismic Array S 0.7 0 0 0.7

Seismic 3C stations P, Pn, Pg, PKP, PKPab, PKPbc, PKiKP 1 0.2 0.2 1.4

Seismic 3C stations pP, sP, pPKP, pPKPbc, PcP, ScP, SKP, SKPbc PP 0.4 0 0 0.4

Seismic 3C stations Sn, Lg, S 0.7 0 0 0.7

Hydroacoustic H 1.54 0 0 1.54

Infrasound Array I 0.8 1 0 1.8




Collocated seismic and infrasound stationsExample: I46RU collocated with ZALV

1. Events built with two collocated (primary seismic station + infrasound array) and one primary seismic station will not be published as REB. Example1: I46RU (I), ZALV (Pg,Pn,Lg,Sn), MKAR (Pn) -> not REB event Example2: I46RU (I), ZALV (Pg,Pn,Lg,Sn), MKAR (Pn), SONM (Pn) -> REB event

2. Events with two collocated (primary seismic station + infrasound array) and one infrasound array should be published as REB events. Example: I46RU (I), ZALV (Pn,Sn), I31KZ (I) -> REB event

3 The same types of phases should not be picked at collocated seismic and infrasound stations Example: “ZALV(I) and I46RU(I)” or “ZALV(Pn) and I46RU(Pn)” are redundant

4. At collocated stations, seismic phases should preferentially be picked at seismic stations, and infrasound phases preferentially picked at infrasound arrays.



Defining attributes

1. Slowness must be non-defining for infrasound arrivals.

2. The infrasound back azimuth is defining if the residual is less than 10°.

3. Infrasound time is defining if the residual is less than 15 minutes.

4. Infrasound back azimuth must be defining when time is defining

5. Purely infrasound events can be saved only if time is defining for at least one infrasound arrival (so that the event can have an origin time).

6. For a multi-technology events, infrasound time should be made defining only when the time attribute is reliable and helps to meet the EDC.



Picking arrivals on infrasound data1. When the signal is impulsive, add or retime the phase based on the

waveforms at the beginning of the peak energy on the beam channel

2. When the signal is emergent, add or retime the phase based on cross-correlation results (PMCC detection pixels).

Impulsive signal from mine near Zalesovo Emergent signal from H-2A rocket launch



Labeling phases

1. The IDC currently makes no distinction for tropospheric, stratospheric and thermospheric phases. All infrasound phases are named 'I'.

2. An event cannot include more than one infrasound 'I' phase per station. 'Ix' is used for additional infrasound phases associated to the event.

3. Seismic arrivals are frequently observed and detected at infrasound arrays. They should be identified and associated when they significantly improve the hypocentre solution.

4. Infrasound phases may be observed and detected (as Noise) on seismic stations. These acoustic phases may be identified as 'I' and associated to events.



Labeling phases (cont.)

5. Single source: The fastest infrasound arrival is labeled 'I‘. Other infrasound phases are labeled 'Ix'.

6. Secondary sources: For large earthquakes (IDC mb magnitude typically greater than 4.5) or moving sources (bolides, rockets): the block of correlated waveforms which better fits with the expected azimuth and time should be picked and labeled 'I'; Any other associated group(s) of infrasound detections should be labeled 'Ix'. Note that these Ix phases often arrive before the I phase.

Example: H-2A Rocket launch from Tanegashima Space Centre, Japan where Ix comes before I phase (next slides)



Photo credit: MHI

H-2A rocket launch from Tanegashima Space Centre, Japan14 Sep 2007 01:31:01GMT

IIx

I

Ix

Tanegashima

IS30

IIx

I53US

I30JP



2 large signalsTraces

Weak signal

2 large signals

No data at the IDC

(Expected)

H-2A rocket launch (Cont.)

Source: http://h2a.mhi.co.jp


Increased Visibility of Infrasound Results

Results of the application of the infrasound procedure- Analyst review of infrasound data is performed when resources are available

- Better recognition of infrasound among the IDC staff

- Results of this collective effort are expected to lead to an operational document

- Visibility of the infrasound results outside the IDC (REB for NDCs)


Increased Visibility of Infrasound Results

- Infrasound detection features accessible on the PTS external database (request for PMCC_FEATURES submitted, implementation depends on DBA resources)

- The PTS is working on a new web infrastructure and services

- Reference event database now includes more than 300 events (IDC analysis + external PTS contracts)

- IDC is in a test phase for infrasound, any suggestions/criticisms are welcome…

Weekly detection bulletin


Software Developments

Interactive Processing• Interactive software for the analyst review of infra signals (ARS-Geotool-PMCC) was implemented in IDC Operations in July 2007

• Visualize - Waveforms - Detections - PMCC pixels• Re-time detections and send back to ARS

• Active PTS contract for enhancement of Geotool-PMCC



Automatic Processing

0 20 40 60 80 100 120 140 160

1

2

3

4

5

6

7

8

9

10

11

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15

Fre

qu

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ban

d #

Duration of the processing window (s)

- Migration of enhanced DFX-PMCC to Testbed and Operations pending hardware upgrade (i.e. Linux OS, not planned before 2008)

- Enhance DFX-PMCC source code for processing low frequencies [0.04-4Hz]

- Establish a baseline configuration for new DFX-PMCC recipes

- Adapt the parameter configuration for the detection categorization module

- Implement DFX-PMCC in the runtime system of the (Linux) development area (September 2007)

- IDC baseline portable source code (iBase) in Operations since November 2006



Impact of the low frequency infra detections on SEL3 events

Detection Processing 0.04 – 4HzSEl3 Events for 15-22 October 2007

Detection Processing 0.1 – 4HzSEl3 Events for 11-17 September 2006

38 infra arrays contributing to 28% of the SHI events(avg. 47 events with infra arrivals / day)

35 infra arrays contributing to 20% of the SHI events(avg. 28 events with infra arrivals / day)

To be done … • More analysts' review of the automatic events and tuning of the existing association criteria• Identify additional criteria to reduce the number of SEL3 infra events



R&D: Atmospheric modelingUnderstand and improve the propagation models of infrasound waves

for prediction of infrasound travel time, phase name, and azimuth deviation.

Delivery from PTS contract with ISLA and NRL • Software for merging ECMWF and MSISE/HWM atmospheric specifications

• Interactive Taup radarplot tool to display G2S-ECMWF predictions

• Linux command line interface of G2Smodel: TauPc suite

Testing and Validation

• Use infrasound reference event database to test radarplot (so far not conclusive)

• Test/validate TauPc command line interface

• Define/test a strategy for real-time operational environment at the IDC (see next slide)



Interactive ReviewRadarplot

1’45’’

(for testing purpose only)

Option 2 (x ndet.)Option 1

26’’1’20’’

G2S-ECMWF (27Mb) All sta., every 3 hours

Atmospheric specifications

Database

TauPc

ECMWF (62Mb)Every 3 hours

NOAASolar flux & Geomag. indices

(F10.7, F10.7a, Ap)

2’00’’

merge

ExtractProp. Characteristics

(for 1 sta.,1az, 1 speed)

(x ndet.)Taupall (3Mb)

2-D Taup prop. characteristicstt,azdev,turn.height

for 1 sta., all azim., all speeds

Taupdir (27Kb)

1-D Taup prop. characteristicstt,azdev,turn.height

for 1 sta., 1 az., all speeds

Automatic/Interactive processing

Example of possible use of real-time atm. specifications in IDC Operations

Station ProcessingDFX-PMCC



Expected back azimuth: 337.7 deg (REB)Measured back azimuth: 348.8 deg

Projection ofpixels on the map

Example: Chile earthquake 21 April 2007, detected at I02AR (1100km)



G2S-ECMWF prediction: Is with -9.3 deg azimuth deviation

PMCC pixels projected on the map after applying -9.3deg azimuth correction

Chile earthquake 21 April 2007 (Cont.)



Chile earthquake 21 April 2007 (Cont.)

The new solution predicted by G2S-ECMWF fits very well with the topography of the Andean Cordillera


Summary

Larger contribution of infrasound data to the REB in 2007• Initial infrasound procedures and guidelines were proposed for analyst review

• An infrasound working environment has been temporally set up (on devLAN) in such way that it does not interfere with analysts’ routine operations

• New interactive tools have been developed to facilitate the infrasound event analysis, including ARS-Geotool-PMCC implemented in IDC Operations

Automatic processing• PMCC processing has been extended to low frequencies (0.04Hz-4Hz) in the runtime system of devLAN and detection categorization configured to work with it

• Many valid automatic events are built with infrasound data, but work remains to reduce the number of bogus events

• Current limitations:

• Limited human resources to review events

• New developments pending hardware upgrade (Linux)

• R&D continues in infrasound propagation in a near real-time operational system

Documents

Infrasound Technology Workshop Tokyo, Japan November 2007