Procurement Executive - Ministry of Defence

AWRE , Aldermas ton

AWRE REPORT NO. 052/74

Some Seismic Results o f the RIO BLANC0 Explosion in the Colorado River Region, USA

(Shot Report No. 5)

P G Gibbs C Blarney

SBN 85518076 5

FOREWORD

During the course of a speech t o the United Nations on 5 th December 1968, Ambassador William C Foster , United S t a t e s representa t ive on Committee I on disarmament, made the following statement:-

"As demonstrated by a c t i v i t i e s such a s these , the United S t a t e s is continuing t o devote considerable resources t o seismic research s o as t o improve t h e c a p a b i l i t y t o de tec t and i d e n t i f y underground seismic events . However, i t is a f a c t t h a t , with the e x i s t i n g technology, w e a r e unable t o gather a l l avqi lable seismic da ta a t long d is tances . We a r e unable a t such d is tances t o d e t e c t o r loca te accurately a l l seismic events o r t o i d e n t i f y pos i t ive ly whether c e r t a i n seismic s igna l s come from earthquakes o r man-made explosions.

Fortunately, the re is c l e a r l y a widespread d e s i r e - f u l l y shared by t h e United S t a t e s - f o r f u r t h e r advancement i n seismic technology and f o r increased i n t e r n a t i o n a l exchange of information i n t h i s f i e l d .

It is i n keeping with t h i s d e s i r e t h a t I should l i k e t o present today a proposal which the United S ta tes considers could do much t o advance objec t ives i n these areas. The United S ta tes proposes t h a t some underground nuclear explosions be conducted with the c o l l a t e r a l ob jec t ive t h a t these serve as explosions f o r world-wide seismic inves t iga t ion . This inves t iga t ion is one i n which a l l S ta te s with the appropriate seismic instrumentat ion could p a r t i c i p a t e . Indeed, the success of t h i s proposal would depend i n l a r g e measure on the extent of world-wide p a r t i c i p a t i o n i n the c o l l e c t i o n and evaluat ion of the seismic data."

One contr ibut ion by the United Kingdom t o the proposal is the publ ica t ion of the p r i n c i p a l da ta recorded by. four seismometer a r ray s t a t i o n s which supply da ta r egu la r ly t o the AWRE Blacknest Seismological Centre. Three a r ray s t a t i o n s a r e cont ro l led respect ive ly by the Department of Energy, Mines and Resources, Canada, the Bhabha Atomic Research Centre, Trombay, Ind ia and t h e Austral ian National University, Canberra, Aust ra l ia . The four th s t a t i o n , Eskdalemuir ar ray i n Scotland, is contro l led by Blacknest.

The publicat ions w i l l be used t o summarise da ta recorded from explosions of i n t e r e s t f o r which f u l l d e t a i l s of locat ion , depth and y i e l d a r e ava i l ab le . I f t h e opportunity occurs da ta from other seismological s t a t i o n s w i l l a l s o be included.

S D Abercrombie Senior Superintendent Detect ion Systems

Shot Report No. 1: P D Marshall, E W Carpenter, A Douglas and J B Young: "Some Seismic Results of the LONGSHOT Explosion". AWRE Report No. 067166, HMSO

Shot Report No. 2: P D Marshall: "Some Seismic Results of the MEDEO Explosion i n the Alma Ata Region of the USSR". AWRE Report No. 033170, HMSO

Shot Report No. 3: D J Corbishley: "Some Seismic Results of the US GASBUGGY and RULISON Underground Nuclear Explosions". AWRE Report No. 046170, HMSO

Shot'Report No. 4: P G Gibbs and C Blarney: "Same Seismic Results of 12 Underground Nuclear Explosions a t the Nevada Test S i t e , USA". AWRE Report NO. 032172, W O

7

SUMMARY

This repor t provides seismological da ta from the underground t r i p l e nuclear explosion known a s R I O BLANCO recorded by ar rays i n Aust ra l ia , Braz i l , Canada and Scotland, and s i n g l e seismometers i n England and South Africa. The sho t was detonated i n Colorado, USA and the loca t ion , depth, source medium and y ie ld have been published by t h e United S t a t e s Atomic Energy Commission.

1. INTRODUCTION

R I O BLANCO is t h e t h i r d i n a s e r i e s af explosioss detonated i n t h e Colorado Plateaux by the United S ta tes Atomic Energy Commission as follows : - GAS BUGGY 10December1967 2 6 k t o n ) Shot

) Report RULISON 10 September 1969 40 kton) No, 3

RIO BLANC0 17 May 1973 90 kton [ l ] (3 of 30 kton each - i n a v e r t i c a l l i n e ) .

These en te rp r i ses were ca r r i ed out j o i n t l y with commercial o i l companies t o inves t iga te the f e a s i b i l i t y of r e l eas ing n a t u r a l gas from comparatively impervious ("tight") s t r a t a . Figure 4 shows the r e l a t i v e pos i t ions of these explosions a s we l l a s a number of o the r ' exp los ions i n and around Colorado, which include the CLIMAX experimental explosion [2] , t he ROCKVILLE DAM explosion [3] and severa l mining sho t s .

Figure 5 is an equidis tant azimuthal grea t c i r c l e projec t ion of t h e world, centred on RIO BLANCO, showing the r e l a t i v e pos i t ions of the various recording s t a t i o n s used i n t h i s repor t and the explosion. Four of the recording s t a t i o n s , EKA, YKA, WRA and BDF, a r e l i n e a r ar rays [4] and a r e i l l u s t r a t e d i n f igure 6. The o ther two-tations, WOL and SWD, have recording vau l t s a t a sing-le locat ion.

Table 1 l is ts t h e i n t e r s e c t i o n poin ts of t h e two arms of the l i n e a r a r r a y s , and t h e o the r recording site pos i t ions .

TABLE 1

Yellowknif e , Canada l (YKA) 62' 29' 35.62" N 114' 36' 19.08" W

Eskdalemuir, Scotland (EKA) 55' 19' 59.48" N 3' 9 ' 31.52" W

Tennant Creek, Aus t ra l i a (WRA) 19' 56' 52.08" S 134' 21' 02.88" E

B r a z i l i a , B r a z i l (BDF) 15' 39' 49.8" S 47' 54' 12.0" W

Wolverton, England (WOL) 51' 18' 45-77'' N 1' 13' 22.1.0" W

Swaziland, South Afr ica (SWD) 26' 24' 00" S 31' 46' 00" E

The d i s t ance , azimuth and back bearing between R I O BLANC0 and each of these recording s t a t i o n s , a s computed with t h e GEDESS computer program [5] , a r e given i n t a b l e 2.

TABLE 2

De ta i l s of Recording S i t e s

S t a t i o n Distance, / 1 Degrees

YKA EKA WRA BDF WOL SWD

Back Bearing, Degrees

Code name

Date

Origin time - S i t e Lat i tude

Longitude

Depth, Rela t ive t o Ground Zero

Geological Medium

Yield

Azimuth, Degrees

TABLE 3

Shot De ta i l s

RIO BLANC0 [6]

17 May 1973

16 00 00 .O GMT

Shale and Sandstone

3 each 30 kton (= 90 kton)

The a r r ays a r e s i t e d p r i n c i p a l l y t o record s i g n a l s from Europe and Cent ra l Asia, w i th in d i s t ances of 90". The Aus t r a l i an a r r a y (WRA) and t h e Swaziland S t a t i o n (SWD) a r e more than 117' from R I O BLANCO, s o the f i r s t a r r i v a l s a t t hese s t a t i o n s a r e branches of t h e P s i g n a l [7] which have t r ave r sed t h e e a r t h ' s core (PKP). I n computing magnitude m,, f o r t he recordings a t t hese two s t a t i o n s , t h e d i s t ance co r r ec t ions f o r magnitude B ( A ) published by Sweeter and Blandford [81 were used. The time d i f f e rences observed minus computed (0-C) ( see t a b l e 4(a) ) given f o r these s i g n a l s r e f e r t o t h e main (D) branch of PKP. J e f f r e y s and Bullen t r a v e l t imes were used [7 I .

The delayed and summed records of t he explosion s i g n a l from each a r r a y a r e shown i n f i g u r e 1. Figure 2 shows t h e s i g n a l s from s i n g l e seismometers a t Wolverton and Swaziland and response curves f o r t hese systems are given i n f i g u r e s 7 and 8. (The s i g n a l was n o t de t ec t ed by t h e Indian a r r a y (GBA) which is i n the core shadow, A = 128O.)

The WOL LPSP and SWD records i l l u s t r a t e d i n t r a c e s (a) and (c ) of f i g u r e 2 a r e t i g h t l y f i l t e r e d vers ions of t h e d i r e c t output of a long per iod v e r t i c a l component seismometer a t each s t a t i o n , whi le f i g u r e 2(b) shows t h e output from a s i n g l e v e r t i c a l s h o r t per iod seismometer a t WOL having a n a t u r a l per iod of 1.67 Hz.

Figure 3 shows the long period su r f ace waves recorded a t Yellowknife long period a r r ay . The su r f ace wave magnitude % ( s e e t a b l e 4(b) ) has been ca l cu la t ed using t h e method recommended by Marshall. and Basham [g]. Figure 9 shows t h e response curve f o r t h i s system.

I n f i g u r e s 1 t o 3 guide l i n e s ( a s shown above) have been added t o i n d i c a t e t h e $ cyc le measured f o r amplitude determinat ion.

T = Period of 8 cycle used.

A = Deflec t ion from which amplitude was ca l cu la t ed .

ACKNOWLEDGMENTS

The recordings a t t h e overseas s t a t i o n s were made poss ib l e by t h e co-operation of t h e Earth Physics Branch, Department of Energy, Mines and Resources, Ottawa, Canada; t h e Aus t r a l i an National Universi ty , Canberra, Aus t r a l i a ; and t h e Department of Geosciences, Univers i ty of B r a s i l i a , B r a z i l ( v i a t h e good o f f i c e s of the I n s t i t u t e of Geological Sciences, Edinburgh).

TABLE 4

(a) Short Period ~esults (Body Waves)

P P --p-

0 = observed, C = computed.

(b) Long Period Results (Surface Waves) Yellowknife (YKA)

Note: The value of magnitude % = 5.48 given for YKA is derived from a single seismometer signal, as the summed signal illustrated in figure 1 includes some slightly overloaded.charanela.

Recording Site

Local

Mile 12

N of Blue 10

Period, S

17.5

17.5

15.5

Amplitude, mlJ

1393

1598

1384

Magnitude,

4.25

4.31

4.25

REFERENCES

Earthquake Data Report. United States Department of Commerce, NOAA, EDR No. 37-73 (6 July 1973)

UED Seismic Data Laboratory Report No. 106, "CLIMAX". 23 May 1964: Long Range Seismic Measurements (22 July 1964)

UED Seismic Data Laboratory Report No. 158, "ROCKVILLE DAM". 3 April 1966: Long Range Seismic Measurements (19 August 1966)

C G Keen, J Montgomery, W H H Mowat, J E Mullard and D Platt: "British Seismometer Array Recording Systems". C Radio and Electronic Engineer, 30, 5 (November 1965)

J B Young and P G Gibbs: "GEDESS: A Series of Computer Programs for Deriving Information at Selected Recording Sites for Signals £rom Known ~ypocentres". AWRE Report No. 054168, HMSO

R Hunter: "Seismic Data for Rio Blanco". NOAA Technical Report ERL 294-ELS 32 ( M y 1973)

H Jeffreys and K E Bullen: "Seismological Tables 1970". British Association for the Advancement of Science, Gray Milne Trust, London Office of the British Association, Burlington House, London W. 1

E J Sweeter and R R Blandford: "Seismic Distance - Amplitude Relations for Short Period P, Pdiff, PP and Compressional Core Phases for A > 99°1'. SDAC-TR-73'=V'(November 1973)

P D Marshall and P W Basham: "Discrimination between Earthquakes and Underground Explosions Employing an Improved M S scalei'. Geophys J Roy Astr Soc, 28, 431-458 (1972)

I .

Seismic Arrays

YKA - J 1

WRA ~

BDF

PIGURE 1, SUMMED SIGNUS (UNFILTERED) OF R10 BLANC0 AT THE ARRAY STATIONS ~

Single Seismagraphs

LPSP I 10 a

WOL - A ' !: A

I'

t Y

FIGURE 2. SINGLE SEISMOMETER RECORDINGS FROM STATIONS WOL AWD SWD

FIGURE 4. LOCATION OF THE RIO BLANC0 EXPLOSION ~ (REFERENCE L61 W A S USED IN THE PREPARATION OF THIS FIGURE)

11 .

FlGUR E 7. MAGNIFICATION SHORT PERIOD ARRAYS

10-q

l

RESPONSE AT T = 1sec:-

1.0

z E! l- a 0 - U z C3 a I W > - l-

4 W a

0 -1

0.01 0 -1 l ro

I 10

PERIOD, S

I

\

\

FIGURE 8. MAGNIFICATION OTHER SHORT PERIOD SYSTEMS

FIGURE 9 . THE RESPONSE OF THE YELLOWKNIFE LONG PERIOD ARRAY SElSHOMETERS

IOK

h

gu \ >

t 0 Irl

k J a W P U

z 0 - t C) - L - z C3

f

1 K

PERIOD, S

I I I I I I I I I I I 1

- - IOK -

- - - - - - -. -

-

-

-

0 10 2 0 3 0 40 5 0 6 0

Unclassified Overall secur i ty c lass i f ica t ion of sheet .-................*.................................................... (h f a r as possible t h i s sheet should contain only unclaasified Inforaatioh. I f it is necessary t o enter c lare i f iad information, the box concerned muat be w r h d t o indicate the c lare i f ica t ion eg (R), (C) or (S)).

1. DRIC b f e r e n c e ( i f b c m )

-

5. Originator's Code ( i f known)

5a. Sponsoring Agency's Code ( i f known)

-

2. Originator's Raf erance

A W Report No. 052/74

7,. T i t l e Some Seismic Results of the R I O BLANC0 Explosion i n the Colorado River Region, USA. Shot Report No. 5

7a. T i t l e i n Foreign Language ( in the crse of Tramlation)

- 7b. Presented a t (for Conference Papers). T i t l e , Place and Date of Conference

-

6. Originator (Corporate Author) U- and ~ o c a t i o n

Atomic Weapons Research Establishment, Aldermaston, Berkshire

6.. Sponsoriag bency (Contract Authority) N.pra and Location

3. -cy Reference

- 4. Report Security

Classification On Sale

10. Date PP ref

January 1975 17 9

14. Other References

-

S. Author l.Surname, I n i t i a l s

Gibbs P G

il. contract Number

-

15. Distribution Statement

No r e s t r i c t i o n

16. h r c r i p t o r a (or Kegworde) (TggT)

Seismic Detection Seismic Arrays Ground Based Detectors Nuclear Explosion Detection

Abetract

This repor t provides seismological da ta from the underground t r i p l e nuclear explosion known as R I O BLANC0 recorded by arrays i n Austral ia , Brazi l , Canada and Scotland, and s i n g l e seismometers i n England and South Africa. The shot was detonated i n colorado, USA and the location, depth, source medium and y ie ld have been published by the United S ta t e s Atomic Energy Commission.

90. Author 2

Blamey C

12. Period

9b. Authora 3, 4 .... -

13. Project

-