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1 International Data CentrePreparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization

Processing of the new Infrasound Arrays Processing of the new Infrasound Arrays on the IDC Testbed - Initial Experienceon the IDC Testbed - Initial Experience

Nicolas BrachetAcoustic officer, CTBTO/IDC/SM

Preparatory Commission for theComprehensive Nuclear-Test-Ban Treaty OrganizationProvisional Technical SecretariatVienna International CentreP.O.Box 1200A-1400 [email protected]

Presented at the Infrasound workshop in Kona, HawaiiNovember 2001


Outline of the talkOutline of the talk

• Data received and processed at the IDC

• Infrasound processing at the IDC

• Goals and motivations for improvement of the system

• Case studies

• Problems in the processing of infrasound data at the IDC


Incorporation of new IMS stations in IDC processingIncorporation of new IMS stations in IDC processing

• IDC is using two processing pipelines in parallel• Operations: automatic and interactive analysis performed on a daily

basis - generates the IDC products for distribution• Testbed: mirror of Operations used as a testing environment (software

development, software configuration, integration of new stations in the processing)

• In 2001, IDC is processing the data from 6 IMS infra stations• IS07 (Australia): September 2001 (Testbed), October 2001 (Operations)• IS08 (Bolivia): August 2001 (Testbed), November 2001 (approved for

ops)• IS10 (Canada): September 2001 (Testbed), October 2001 (Operations)• IS26 (Germany): April 2001 (Testbed), October 2001 (Operations)• IS34 (Mongolia): August 2001 (Testbed)• IS57 (USA): October 2001 (Testbed)


Goals and motivationsGoals and motivations

• Improvement of the know-how in infrasound processing• Need for a better understanding of the signals

Establishment of a catalog of reference events

A few case studies presented in this talk

• Becoming familiar with the latest methods in infrasound processingAssessment of existing tools used at the IDC

New developments in infrasound signal processing

(in 2001, cooperation with French NDC: PMCC is being tested at the IDC)

• Station tuning• Currently at the IDC: standard configuration used for all stations• Need to include station specifics in the processing

Assessment of the detection capability for each station


Reference events collected in 2001 at the IDCReference events collected in 2001 at the IDC

•Pacific bolide (23 Apr 2001)

•Earthquakes in Peru (23 Jun, 26 Jun, 7 Jul 2001)

•Eruption of the Etna volcano, Italy (Jul 2001)

•Explosion at a chemical factory in Toulouse, France (20 Sep 2001)

•Mining activity in Canada (11 Sep 2001)


Case study: Pacific bolide (23-Apr-2001)Case study: Pacific bolide (23-Apr-2001)

From Whitaker’s presentationin Wyoming, Oct 2001

PMCC interactive (IDC)

Station Distance Time ofmax.

amplitude

Azimuth(deg.)

TraceVelocity

(m/s)

Detectiontime

Azimuth(deg.)

TraceVelocity

(m/s)NVIAR 1753 km 07:56:21 236.1 341 +/- 2 07:52:28 236.9 +/- 1.8 340 +/- 3

SGAR 2039 km 08:12:30 252.0 358 +/- 69 08:10:38truncated

251.2 +/-1.6 298 +/- 10

IS59 2526 km 08:27:56 62.5 340 +/- 15 08:18:03 62.4 +/- 2.8 338 +/- 8

DLIAR 2626 km 08:44:43 259.3 337 +/- 18 08:39:48 259.8 +/- 1.5 340 +/- 8

IS10 3931 km 09:58:47 244.2 - 09:55:29 242.9 +/- 0.8 295 +/- 16

IS24 5350 km - - - no - -

IS08 8600 km - - - no - -

IS25 8900 km NA NA NA NA NA NA

Flers 10315 km 15:45:00 314.6 291 15:46:26 314.8 +/- 2.0 337 +/- 9

IS26 9526 km 16:26:00 327.3 346 +/- 5 16:24:40 324.8 +/- 3.3 342 +/- 13

IS07 11200 km - - - no - -

Validation of PMCC results on a well-studied event


Case study: seismic event in Peru (Jun-Jul 2001)Case study: seismic event in Peru (Jun-Jul 2001)

IS08

Titicaca lake

Ms=8.2

Ms=6.8

BOLIVIA

PERU

Topography data: USGS DEM & Cornell Andes Project

100 km

23-Jun-200126-Jun-200107-Jul-2001

Ms=6.9

Ms=7.5

Event detected at a distance of 500km at IS08 (Bolivia)


Case study: seismic event in Peru - Case study: seismic event in Peru - 23 Jun 200123 Jun 2001

seismic

1 2 4 6

seismic

3 5

Results of PMCC analysis


Case study: seismic event in Peru - Case study: seismic event in Peru - 23 Jun 200123 Jun 2001 (Cont.) (Cont.)

Event#

Ho Lat Lon Depth(km)

mb (Ms) Distance(km)

Az exp.(deg)

Det. Time Phase Az meas.(deg)

App. Vel(km/s)

1 20:33:10 -16.24 -73.43 5.9 (8.2) 532 269.0 20:34:5320:35:0320:39:0820:45:0820:51:2320:56:5821:03:53

Seismic PSeismic LR

I*I*I*I*I

259.4251.1253.4243.3253.6269.9272.1

6.54.5

0.3460.3460.3830.3520.372

2 20:51:40 -17.14 -72.75 4.8 469 256.8 - - - -3 20:54:49 -16.38 -73.53 5.1 542 267.4 21:24:19

21:28:01II

278.1278.3

0.3460.367

4 20:56:06 -17.35 -72.21 19.4 5.3 419 252.1 21:19:5421:24:41

II

276.9280.0

0.3580.374

5 20:59:46 -16.97 -73.46 4.9 540 260.4 - - - -6 21:03:43 -17.72 -72.04 4.7 416 245.9 - - - -7 21:04:18 -16.64 -73.87 4.8 580 264.6 - - - -8 21:05:40 -17.92 -71.50 34.8 4.9 375 239.4 - - - -9 21:10:39 -17.54 -71.42 4.8 348 244.7 - - - -

10 21:14:02 -17.26 -72.80 4.7 477 255.4 - - - -11 21:24:02 -17.30 -71.72 4.5 368 250.5 21:45:35 traces 257.3 0.37112 21:27:37 -17.10 -72.56 27.5 5.2 449 256.8 21:50:45

21:52:35II

252.5263.6

0.3490.347

13 21:38:46 -17.07 -72.29 4.9 420 256.4 - - - -14 22:32:33 -17.56 -72.54 5.2 460 250.6 - - - -15 23:09:57 -16.61 -73.52 5.5 (6.9) 542 264.7 23:13:10

23:34:2023:38:33

Seismic LRI*I

279.0268.6276.1

3.9090.3500.348

• Most seismic events with mb>5 detected at IS08

• Phases detected: Seismic waves (P and Rayleigh) for large events

• Many infrasound phases arrive earlier than expected (I*)

• REB events in Peru detected by PMCC at IS08


Case study: seismic event in Peru - Case study: seismic event in Peru - 07 Jul 200107 Jul 2001

Ho Lat Lon Depth(km)

Mb (Ms) Distance(km)

Az exp.(deg)

Det. Time Phase Az meas.(deg)

App. Vel(km/s)

09:38:40 -17.39 -71.99 5.5 (7.5) 399 250.3 09:40:0009:44:2509:45:5009:47:1009:49:0509:52:3509:55:1009:56:4009:58:0010:01:40

RayleighI*I*I*I*I*I*I*II

240.2252.3233.7256.6287.5225.1259.5208.7266.9268.5

4.6860.3340.3290.3090.3020.3430.3400.3410.3550.351

Det.time Phase Az meas.(deg)

App. Vel(km/s)

SNR cfreq FSTAT FKQual

09:40:5309:41:1009:41:29

NNN

266.0 +/- 35.7256.8 +/- 31.5250.4 +/- 27.1

5.6535.2074.298

4.66.06.2

0.30.30.3

18.751.616.9

121

• PMCC produced the same type of results as for June 23 event

• Libinfra-PIDC detected only the seismic arrivals

Comparison of results for REB event in Peru (07 Jul 2001)

Note: phases identified as Noise by StaPro (cannot be associated to an automatic event)


Case study: seismic event in Peru - Case study: seismic event in Peru - 07 Jul 2001 (Cont.)07 Jul 2001 (Cont.)

1

2

3

3

2

Polar diagram of the infra arrivals

seismic infra1 21’ 3

11’

1’Ms=7.5

IS08

REB Event

The Andean cordillera behaves like multiple infrasound sources activated by the seismic wave front

Azimuth variation reflects the geomorphology of the Andes


Infra-Seismic stations co-located in CanadaInfra-Seismic stations co-located in Canada

Mining activities recorded at the Canadian stations: IS10 + ULM

Lake Winnipeg

Lake Superior

IS10

200km

400km

ULM


PMCC analysis at IS10 PMCC analysis at IS10 (Canada)(Canada)


Identification of the events recorded at IS10Identification of the events recorded at IS10M

ES

AB

I R

AN

GE

(40

0km

SE

)

LO

CA

L M

INE

S

Categorization of station-specific events

200k

m N

E


Infrasound and meteorology: microbaroms at IS26 Infrasound and meteorology: microbaroms at IS26 (Germany)(Germany)

• Detections with similar characteristics over a long time period

• Detections produced by DFX-Libinfra, confirmed by PMCC

• No correlation with any microbaroms at Flers (France)

• Meteorology data: storm in the North Sea the same day


• Possible cause of the problems • Software related: algorithm, configuration• Data related• Case of IS26 (Germany)

Problems with data processing at the IDCProblems with data processing at the IDC

Number of daily detections

0 1-10 11-50 >50 Total

IS07 days(%) days

93%26

7%2

0%0

0%0

100%28

IS08 days(%) days

66%53

30%24

4%3

0%0

100%80

IS10 days(%) days

9%6

29%20

52%35

10%7

100%68

IS26 days(%) days

63%137

19%41

9%21

9%19

100%218

IS34 days(%) days

80%62

18%14

1%1

1%1

100%78

• Low and irregular number of detections observed for all infrasound stations processed at the IDC


Problems with data processing at the IDCProblems with data processing at the IDC (Cont.)(Cont.)

• Asynchronous Testbed and Operations pipelines• Data is forwarded from ops to Testbed in near real time• Data is organized in time intervals of 30min for infra• Intervals are scheduled for processing when they contain a sufficient

amount of data– Problem 1: Intervals are processed in near real time: all data needed may

not be available for use at the time it is processed– Problem 2: Interval generation and execution is asynchronously done on

ops and Testbed

• Consequences for the detection process:• Ops and Testbed may process different data• Ops and Testbed may produce different detections


Problems with data processing at the IDC - ExampleProblems with data processing at the IDC - Example

Testbed : I26DE (processing time interval [16:00 - 16:30] on October 16, 2001)

++ tuxshell 2001-10-16 16:34:10 time=1003248000.000 endtime=1003249800.000 name=I26DE get_infra_processing_interval: Requested processing interval 1003248000.000 to 1003249800.000 get_infra_processing_interval: Computed processing interval 1003247999.983 to 1003249632.033 get_infra_processing_interval: Actual waveform data interval 1003247860.885 to 1003249839.957-- tuxshell 2001-10-16 16:35:01 time=1003248000.000 endtime=1003249800.000 name=I26DE

Operations : I26DE (processing time interval [16:00 - 16:30] on October 16, 2001)

++ tuxshell 2001-10-16 16:34:26 time=1003248000.000 endtime=1003249800.000 name=I26DE get_infra_processing_interval: Requested processing interval 1003248000.000 to 1003249800.000 get_infra_processing_interval: Computed processing interval 1003247999.983 to 1003249712.033 get_infra_processing_interval: Actual waveform data interval 1003247860.885 to 1003249919.957-- tuxshell 2001-10-16 16:35:20 time=1003248000.000 endtime=1003249800.000 name=I26DE

Det.time Phase Azimuth Slowness SNR FSTAT FKQual16:02:38 I 282.63 2.84 2.87 17.95 1

16:12:53 I 292.37 2.83 2.92 12.78 1

16:27:47 I 284.45 2.89 6.7 16.65 4

Det.time Phase Azimuth Slowness SNR FSTAT FKQual16:02:38 I 282.63 2.84 2.84 17.99 1

16:12:53 I 292.37 2.83 2.95 12.78 1

16:24:41 I 279.22 2.90 2.83 27.26 3


Problems with data processing at the IDC (Cont.)Problems with data processing at the IDC (Cont.)

Nominal timestampof the data frame

Start_time of subframe

Irregular Data frames (within 1 sample) 20s shift in wfdisc segments

1 sample (0.05s)

Channel subframe

20 seconds

All channel subframes of a Data Frame will have the same start time and duration to within one sample time unit. […] The nominal time field is set equal to the start time of the earliest channel subframe [...] on an interval multiple of 10 seconds and synchronized to the minute (Format and Protocol for Cont. data CD-1.1).

• Digitizing problems at IS26 causes asynchronous wfdiscs



12345 12345 12345 12345 12345 12345

5 chans 4 chans 3 chansNumber of synchronous channels:

• The number of detections is lower when Wfdisc segments are asynchronous



Presence of multiple peaks on all channels

• origins of the peaks?

• impact on the processing?

Spectral analysis at IS26


SummarySummary

Infrasound signal analysis is a difficult exercise: collection of reference events is necessary • To increase the experience and knowledge in signal processing and

event recognition• Familiarization with the detection capability of IMS stations • First step before starting a comprehensive station tuning

Assessment of the analysis tools:• Existing automatic system (detection/association)• PMCC interactive tool for signal analysis

Problem of low number of detections produced at the IDC• Related to the software• Related to the configuration parameters (tuning)• Related to the data

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