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AD-761 813

EXTENDED ARRAY EVALUATION PROGRAM

Terence W. Harley

Texas Instruments, Incorporated

Prepared for:

Advanced Research Projects Agency Air Force Technical Applications Center

15 January 1973

DISTRIBUTED BY: \m National Technical Information Sonrico U. S. DEPARTMENT OF COMMERCE 5285 Port Royrt Road, Springfield Vi. 22I5I

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Extended Array Evaluation Program, Quarterly Report No. 3

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Terence W. Harley

15 Januarv 1973 ••. CONTRACT ON GRANT NO. ^

•• RRO..CT N<i0ntrÄCt No- F33657-72.C-0725

^ AFTAC Project No. VELAT/2705/B/ASD

V. TATAL M P HMI 11

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APPROVED FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED 11.

ARPA Order No. 1714 l>. AMTRACT

»I SRONtORINO MUTSaV ACTIVITY —~~~~''—^~~'~

Advanced Research Projects Agency Nuclear Monitoring Research Office Arlington. Vii-y4nia ?"fl9

This third quarterly report summarizes progress -.-^ r . . r H^n<,

sgays oc

f ^A' ^oiisAR' -- VLPE

P program^ricrm:

1^657-72.0.07«. Work to date in the following area, is summarized:

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ALPA evaluation

NORSAR long period evaluation

NORSAR short per/od evaluation

VLPE evaluation

Network evaluation

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UNCLASSIFIED

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Extended Evaluation of ALP A. NORSAR and VLPE Data '

Quarterly Report No. 3, 1 October 1972 to 31 December 1972

ALPA Evaluation

NORSAR Long Period Evaluation

NORSAR Short Period Evaluation

VLPE Evaluation

Network Evaluation

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APPROVED FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED

AFT AC Project No. VELA T/2705/B/ASD

5? EXTENDED ARRAY EVALUATION PROGRAM

Quarterly Report No. 3

1 October 1972 to 31 December 1972

T. W. Harley, Program Manager Area Code 703, 836-3882 Ext. 300

TEXAS INSTRUMENTS INCORPORATED Services Group

Post Office Box 5621 Dallas, Texas 75222

Contract No. F33657-72-C-0725 Amount of Contract: $417, 000

Beginning 1 April 1972 Ending 31 March 1973

Prepared for

AIR FORCE TECHNICAL APPLICATIONS CENTER Alexandria, Virginia 22314

Sponsored by

ADVANCED RESEARCH PROJECTS AGENCY Nuclear Monitoring Research Office

AR PA Order No. 1714 AR PA Prjgram Code No. 2FI0

IS January 1973

Acknowledgement: This research was supported by the Advanced Research Projects Agency. Nuclear Monitoring Resesrch Office under Project VELA-UNIFORM, and accomplished under the tech- nical direction of the Air Force Technical Applications Center under Contract No. F33657.72-0-0725.

, NATiONAl TECHNJCAl INFORMATION SERVICE

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TABLE OF CONTENTS

TITLE

INTRODUCTION AND SUMMARY

ALPA EVALUATION

A.

B.

CURRENT STATUS

FUTURE PLANS

NORSAR LONG-PERIOD EVALUATION

A. CURRENT STATUS

B, FUTURE PLANS

NURSAR SHORT-PERIOD EVALUATION

A. CURRENT STATUS

B. FUTURE PLANS

VLPE EVALUATION

A. CURRENT STATUS

B. FUTURE PLANS

NETWORK ANALYSIS

A. CURRENT STATUS

B. FUTURE PLANS

PAGE

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Technik ^ MM ? R—.rch ProJ.ct. Af.ncy nor th. Air Forc.

herein which h.. »>•.„ .uppli.d by other - g.ni.Ätion. or contractor, ^d thi. document i. .abject to Uter reviHon Z m.y be nece...rj The v^w. .nd conciu.ion. pre.ented are tho.e of *, author, and .houid'not ^ in eT ?*****-»** '•P'—nting the official poücie.. either e*pre..ed or

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SECTION I

INTRODUCTION AND SUMMARY

This third quarterly report summarizes progress made during

the last quarter, 1 October 1972 to 31 December 1972, on the Extended Eval-

uation of ALP A. NORSAR and VLPE Data Program being conducted by Texas

Instruments Incorporated at the Seismic Array Analysis Center in Alexandria,

Virginia. The program consists of the following five tasks:

Continued evaluation of the Alaskan Long Period Array (ALPA)

Continued evaluation of the long period Norwegian Seismic

Array (NORSAR)

• Continued evaluation of the short period Norwegian Seismic

Array

• Continued evaluation of the stations of the Very Long Period

Experiment (VLPE) network

• Investigation of network processing and analysis techniques.

The software required to perform the evaluation was developed

under a previous contract (Contract F33657.69-C-1063).

ALPA evaluation included the completion of the processing and

analysis of the winter (1 January to 20 March 1972) ensemble and about 130 of

the 380 events from the summer (June-August) ensemble. The total number of

events successfully analysed to date under this contract is approximately 308.

A re-evaluation of S-wave detection threshold for events from the Kuril« Island

Kamchatka region was initiated.

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Evaluation of the long-period NORSAR data continued with

analyi. of the winter event .uite being completed and analy.i. of the summer

suite being started. Approximately 161 events were obtained for the winter

•uite and about 49 events were completed from the summer suite so far.

Group velocity measurements have been obtained for a small group of Italian events.

Major revisions in the subarray beamforming program used in

the NORSAR short-period evaluation task have been completed. Initial results

•how a significant decrease in signal attenuation due to subarray beamforming.

Event processing has resumed with 78 events from the winter ensemble edited and undergoing analysis.

Evaluation of the VLPE stations continued with 239 event, from

June and July having been analyzed. Uaily noise samples for these month, were also analyzed.

Two special reports were generated under the network evalua-

tion task. The first report concern, the amplitude decay of long-period Ray-

leigh wave. a. .een on the VLPE .ei.mogram.. The .econd report de.cribe.

the long-period noi.e at the VLPE locations. Ab.tract. of both report, have

been .uümitted for open publication clearance.

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SECTION II

ALPA EVALUATION

CURRENT STATUS

Through the end of this quarter, 308 out of a total of 686 event,

from the winter and .ummer ensemble, have been procee.ed and analyzed.

The dispo.ltion of the other 378 event, is .hown below.

Total event.

No data available

Bad library tape.

Spiked data

Interference*

Completed event.

Event, in processing

686

5

45

107

308

173

Of the 173 event, remaining to be procee.ed. 26 are from July

•nd 147 from Auguet. Edit, have be.« obtained for 69 event, in Augu.t. Re-

proc.ing of a number of event, from the ISM (2/20/72 - 3/19//2) because of

revl.ion of .ource parameter, re.ulted in an «ncrea.. by 26 i„ the oumb,r of

•vent, lucce..fully proce.ted in that period.

A problem ha. ari.en in the proc...lng of the Augu.t data .et

The low.rat. data library tape, covering the period of about Augu.t 1 to about

Augu.t 19 contain numerous parity error, and timing word error.. The.e

•rror. tend to produce Urg. .plk.. u, lh. dmU thu. pr.cludinf - ^1

—ly.l.. NORSAR data from Ü»... upe. have U.o bee« found to be f.ulty.

Preee«. indica.lnnr are that approaimately one-thlrd of the Aug i.t event, will be rejected becau.e ot this problem.

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I I [ 0 II I B I I I I I I I I I

I A re-evUuation of the S-wave detection capability of ALPA for

event, from the Kurile Island. - Kamchatka area wa. .tarted thi. quarter

There 1. evidence that the detection thre.hold for S-wave. from thi. area may

be .omewhat lower than mb = 5. 0. To date. 58 event« have been reproce..ed for thi. purpo.e.

The inve.tigation of reference waveform matched filtering con-

tinued thi. quarter. Thi. .tudy i. intended to elucidate the relative importance

of v,riou. .ignal parameter, in improving .ignel-to-noi.e ratio, by thi. type of

matched filter. Event, examined .o far have all been from *• Slnkiang region.

B. FUTURE PLANS

Routine proce..ing of ALPA event, will conclude at the com-

pletion of the Augu.t group. Selection and analy.i. of noi.e .ample, will

re.ume u.ing .lightly different procedure, .o that additional information on propagation direction can be obtained.

. . , ^ int«r£«'*ng «vent i. any event which arrive, at the arrav at approximately the .ame time a. the event under analy.i.. and which ^uld ob.cure or alter the waveform of the de.ired event. ^

An interfering event may be detected by noting:

• Ütr??1 "7 ? ALPA- " thlB **** f'om »he e.tlmated K MM *'* eVent Under "^y^- •» ^fr'«ring event ■hould be au.pected.

• the amount of .ignal degradation c.u.ed by the beamforming proce... An off.a«imuth .ignal will be highly attenuated.

• the amplitude and duration of the .ignal. If the.e ..em too

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SECTION III

NORSAR LONG-PERIOD EVALUATION

A. CURRENT STATUS

By the end of this quarter, routine processing of the winter

ensemble of events was completed and processing of the summer ensemble

started. The number of events successfully processed from the winter ensemble

was 161. Processing was almost completed on the June event, with approxi-

mately 85 usable events obtained. Forty-nine of these events have been ana-

lyzed. Editing and beamforming of the July event» ha. been completed with

about 83 events or.t of 113 successfully obtained. Editing of the August events has been started.

The library tape parity error problem discussed in Section II

has also affected editing of August NORSAR data. Since edit processing ha.

just been started, we are unable to say how many events will have to be dis-

carded but is probable that it will be about the same number as for ALPA. or about 50.

Noise analysis was suspended for most of this quarter. This

work has resumed and processing of several potential long-duration noi.e

..mples covering the period through Augu.t has been initiated.

Group velocities of about nine events from Italy have been measured.

B. FUTURE PLANS

Routine processing of NORSAR events will continue. It is

..tlmated that only events through July will be completed by the end of this

quarter however. Noise analysis will continue with analysis of both long-

d-ration and short-duration samples covering the period of January to August.

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SECTION IV

NORSAR SHORT-PERIOD EVALUATION

A. CURRENT STATUS

This quarter, revi.ions in the subarray beamforming program

NORSPECT were completed and normal proce..ing wa. resumed. These re-

visions, which were discussed in the last quarterly report, allow the use of

adjusted time delays rather than plane wave model delays in forming subarray

beams. Preliminary result, from two close events ( < 30°) indicate an average

of 0. 5 dB decrease in subarray beamforming signal attenuation may be obtained.

For two subarrays. signal attenuation was reduced by more than 3 dB by the

elimination of sensors found to have unsuspected polarity reversals.

Seventy-eight events from the winter ensemble have been edit-

ed. These events are ones which have been successfully analyzed using both

ALPA and NORSAR long-period data. Noise samples for three of these events

were edited and subarray beams have been formed for six events.

B. FUTURE PLANS

Twenty-five events remain to be edited from the common ALPA-

NORSAR LP analysis list. Sixteen noise sample, have been selected but not

edited. Processing this quarter will be focused on the analysis of these events and noise samplet.

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SECTION V

VLPE EVALUATION

CURRENT STATUS

One-houi noise aamples for each day and 239 events from the

June-July 1972 ensemble havt been processed and analyzed using the data

from the VLPE stations it Australia. Spain, Israel, Norway, Ogdensburg,

Hawaii, and New Mexico where available. A total of 900 event signals were

examined and 299 were discarded because of bad data or because of interfer-

ence from othör events.

Processing of the August 1972 data is currently in progress.

B. FUTURE PLANS

Routine digital processing will continue for the August 1972

noise samples and ensemble of events. However, the analysis o: these data

will be temporarily halted on January 15, 1973 for the purpose of analyzing,

tabulrting, and reporting results.

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SECTION VI

NETWORK ANALYSIS

CURRENT STATUS

Two special report« concerning VLPE network oper^ti,«« are

in preparation based upon ?naly.l. of .eismograms in preceding rnec^*. The

first special report describes Long-period Rayleigh wave amplitude decay as

observed on the VLPE seismograms: an abstract of the report has been sub-

mitted for clearance for open publication in the Transactions of the American

Geophysical Union. A public presentation of the research results is planned

(once clearance is obtained) at .he Spring meeting of the Americal Geophysical Union in Washington, D. C.

The second special report describes long-term long-period

(13. 5 - 62. 5 second) seismic noise at the VLPE locations. An abstract of

this report has also been submitted for open publication clearance, and public

presentation (upon clearance of text) is planned at the Boulder. Colorado

meeting of th3 Seismological Society of America in May. 1973. Some data

for this report are in the process of being analyzed at present.

An extension to the first report is planned to indicate the poten-

tial for Rayleigh wave interference times in a network of VLPE stations based

upon observed Eurasian seismicity; the second report will be essentially com-

plete with the text submitted for clearance.

B. FUTURE PLANS

Master waveform and chirp filter techniques for improved signal detectability are being initiated.

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