PRECISION OF SMALL NUCLEAR EXPLOSIONS PARAMETERS CONDUCTED AT SEMIPALATINSK TEST SITE BASED ON HISTORICAL

SEISMOGRAMS STUDY

Sokolova I.N. Institute of Geophysical Research, Kazakhstan

(T2-P57)

Many researchers in the field of monitoring for nuclear tests encounter the problem of lacking in technical literature such information about

nuclear explosions parameters as origin time, coordinates and magnitude. For example, official Russian sources contain information about 340

underground nuclear explosions conducted at the STS in the east of Kazakhstan in 1961 – 1989. However, origin time, coordinates and magnitudes are

indicated for 271 UNE only [1, 2]. As a rule, for air and surface explosions the catalogues have only date, yield and very approximate coordinates

(Figure 1).

Huge work on recovering the parameters of low yield underground nuclear explosions conducted at Semipalatinsk Test Site was implemented in

work (V. Khalturin, T. Rayutian, P. Richards, 2001) [2]. They used records of analogue seismic stations of the USSR located at regional distances.

However, even for UNE there is a set of explosions that do not have some parameters.

The situation is more complicated with air and surface nuclear explosions at the STS; the explosions were quite small and had not been recorded

by standard permanent seismic stations. Many of its characteristics remained unknown until recently. The task of the present work was to close the gap

using available data.

Figure 1. A fragment of the catalogue for air and contact nuclear explosions conducted

at the STS.

In 1961-1962 maximal number of air and contact explosions was conducted at Opytnoye Polye site of the STS (Figure 2). At this period IPE AS

USSR installed a profile of high-sensitive seismic stations to investigate the structure of earth crust and upper mantle [3]. The epicentral distance from

some stations of the profile to Opytnoye Polye site was 300 – 400 km. In addition, the records from Semipalatinsk stations (SEM) located at ~ 175 km

away from Opytnoye Polye site became available recently. The present work investigates the parameters of air and contact explosions at the STS by data

of historical seismograms from the profile stations and SEM station.

Figure 2. The map of the test sites location at the STS.

Observation system and used materials.

The total length of high-sensitive seismic stations Pamir – Lena river profile was about 3500 km. Total number of the profile stations was 54, average

distance between the stations was 70 – 120 km [3]. The profile crossed Central Asia, Kazakhstan, Altay, Sayan and near Baykal territory. In addition to the

profile information, data from Semipalatinsk (SEM) station located 175 km away from Opytnoye Polye site were also used. Figure 3 shows the observation

system.

All events at the profile stations were recorded by analogue instruments with direct galvanometric recording with seismic receivers USF, SVK-M, SGK-M

[4]. All stations seismometers were three-component (N-S, E-W, Z) with magnification from 25000 – 120000, however magnification at the most stations

was V=50000. The seismometers USF and SKD with magnification 1000 were installed at Semipalatinsk station. Table 1 shows the main types of

instruments used at analogue stations of the profile and Semipalatinsk station. SKM and USF seismometers had natural period 1.5 or 2 s, D1 attenuation

was 0.4, GB-IV with natural frequency 5-8 Gz with attenuation D2 = 3-3.5 were used as galvanometers [4, 5]. Figure 4 shows an example of analogue

seismogram of air explosion recorded by Mikhailovka station on October 20, 1962, epicentral distance was 333 km.

Figure 3. Observation system in 1961-1962; Pamir –

Lena river profile (CSE IPE RAS) and SEM station

(triangles – seismic stations, star – Opytnoye Polye site).

Figure 4. Analogue seismogram of air explosion recorded by

Mikhailovka station on October 20, 1962, epicentral distance is 333 km.

seismomet

er

Natural

period T0 , s

magnification Scanning rate,

mm/min

Recording

type

Number of

channels

SKD 20 1.0К-1.5К 60, 30 or 15 photopaper 3

SKM 1.5, 2 25К-125К 120 or 60 photopaper 3

USF 1.5 50K-80K 240 or 120 photopaper

3

Table 1. Characteristics of analogue instruments.

Analogue seismograms of explosions conducted at the STS territory were selected from different seismological archives of Kazakhstan and

Kyrgyzstan, scanned and digitized. “NXSCAN” [6] software complex that allows to digitize in semi-automated mode earlier scanned seismograms is used.

The seismograms were digitized with 40 Hz frequency. The fragments of analogue seismograms digitized by NXSCAN software are saved in SAC format

(Seismic Analysis Code) [7], after that these are converted into CSS3.0 format (Center for Seismic Studies v.3.0) [8]. The database is created using digitized

materials.

According to the test results the digitized seismograms conform well visually and by kinematic and dynamic parameters to the original. Figure 5

shows the diagram of source type distribution of digitized records of explosions conducted at the STS.

The database of digitized seismograms of air and surface nuclear explosions contains 309 records from 24 seismic stations at distances 175-1480 km.

Figure 6 shows seismograms of air explosion of November 14, 1962 conducted at 660 m height of 12 kT yield. The explosion parameters were

restored by digitized records t0=11-32-15.6, =50.4227, =77.7231, mpva=2.8, energy class K=8.7. The records of air and contact explosions at Opytnoye

Polye site of the STS have all signatures of air explosions, high-amplitude surface waves, weak P arrival, S/P ratio more than 1, many seismograms have a

record of acoustic wave (Figure 7).

263

46

2923

132

air nuclear explosions

surface nuclear explosions

underground nuclear explosions

chemical explosions

Figure 5. Distribution of digitized seismograms from

the STS territory by the source type (1961 – 1989).

Figure 6. Seismograms of air explosion of

November 14, 1962, t0=11-32-15.6, =50.4227,

=77.7231, mpva=2.8. Z-component.

Figure 7 а Seismograms of air explosion of

October 20, 1962, t0=09-21-45.6, =50.4227,

=77.7231, by station NCE (328 km).

Figure 7 b A seismogram of air wave

from atmosphere explosion of October

20, 1962, t0=09-21-45.6, =50.4227,

=77.7231, by station NCE (328 km).

The air wave was recorded along the profile by the following stations: Nikolayevka (NCE), Mikhaylovka (MIKH), Karakum (KKUM), Chingyuzha

(CHNG), Leninogorsk (LNGR) at epicentral distances 322-442 km (Figure 8).

42 records of acoustic wave were found and processed. The acoustic wave records (Figure 7b) are clearly seen on horizontal and vertical components

representing oscillations train with periods 1-3 s. Propagation velocity is V~(0.323 ± 0.013) km/s.

Researchers are very interested in dependence of acoustic waves on explosion yield, the amplitudes were measured for MIKH station as this station has

the largest number of records (Figure 9). During analysis, weather conditions and atmosphere model were not considered as it is impossible to restore that

data for years 1961-1962. The height of the explosions was not considered too, it was in the range of 310 – 695 m.

The equation of linear regression for this dependence is:

lg(A)=0.802+0.061*Y at R= 0.68, (2)

where А – amplitude of air wave (nm), Y – air explosion yield (kt), R – correlation coefficient. Air wave amplitude increase depending on explosion yield

is observed.

Figure 8. The map of Opytnoye Polye site

location (star) and seismic stations which records

have an acoustic wave (triangles).

2 4 6 8 10 12 14 16 18 20

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

2,0

2,2

Y,kt

lg(A/T)

Figure 9. Dependence of amplitudes of air wave

record on air explosions yield, MIKH station.

Figure 10 shows the seismograms of explosions conducted in different mediums at the STS and recorded by one station Kzyl-Agach KAC, SKM

seismometer. The upper seismogram is air nuclear explosion of 9.2 Kt conducted at Opytnoye Polye site on October 10, 1962, the distance was 565 km; the

second seismogram is surface nuclear explosion of 9.9 Kt of August 7, 1962 conducted at Opytnoye Polye site, epicentral distance was 565 km; third

seismogram is underground nuclear explosion of October 18, 1984 with yield less than 20 Kt conducted in a tunnel at Degelen site at epicentral distance

494 km; lower trace is chemical explosion at the STS, epicentral distance is 506 km.

The Figure shows that despite the explosions location almost at the same place, the seismograms view differs significantly depending on a source type.

Air and surface explosions have a range of similar features such as domineering surface waves, unclear Pn arrivals, however the seismogram of contact

explosion has higher frequencies comparing to atmosphere explosion. Absolutely different view has underground nuclear explosion: Lg wave dominates,

Pn arrival is clear, the record has high frequencies, surface waves level is very low. The chemical explosion record also has domineering Lg waves, low Pn

level, unclear arrival, Pg dominates among longitudinal waves, and the record has high frequencies.

Figure 11 shows seismograms of explosions conducted in different mediums at the STS and recorded by Semipalatinsk SEM station located in the

east of Kazakhstan. The upper seismogram is air nuclear explosion of 13 Kt conducted at Opytnoye Polye site on October 4, 1961, the distance was 166

km; the second seismogram is underground nuclear explosion of December 14, 1980 of 20-150 Kt yield conducted in a tunnel at Balapan site at epicentral

distance of 166 km from the station; the third seismogram is underground nuclear explosion of June 25, 1980 of yield less than 20 Kt, the explosion was

conducted in a tunnel of Degelen site at epicentral distance 166 km from the station; the lower trace is calibration chemical explosion at the STS of August

22, 1998, the yield was 100 t, epicentral distance – 176 km.

The Figure shows that the seismograms of nuclear and chemical explosions have a range of similar features such as domineering S-wave, clear P-

wave arrivals for nuclear underground and chemical explosions, S/P ration exceeds 1, for air explosion the level of P-wave amplitudes is significantly lower

than for underground one, and the level of surface waves amplitudes is higher than of UNE and chemical explosion.

Figure 10. The different type of records by KAC station from

explosions conducted at Semipalatinsk Test Site (∆~ 500 km). The

upper seismogram is air nuclear explosion, the second seismogram

is surface nuclear explosion, the third seismogram is underground

nuclear explosion conducted in a tunnel of Degelen site, the lower –

chemical explosion at the STS. Channel Z.

Figure 11. The records of different type explosions conducted at

Semipalatinsk Test Site and recorded by SEM station (∆~170 km). Up

down: the seismogram of air explosion, underground nuclear explosion

conducted in a tunnel of Balapan site, underground nuclear explosion in

a tunnel of Degelen site, chemical explosion at the STS. SKM filter, Z -

channel.

mpv was calculated following the formula:

mpv = lg(Ap/Tp) + reg(),

where reg()- is regional calibration function; - epicentral distance, km; А –amplitude of P-wave shift by Z-component; Т – period.

Calculation of energy class by the formula:

K= 1.8 lg (Ap + As) + σ1 (Δ), where 1()-calibration function for energy class calculating; Ap and As – maximum amplitudes in phases of P- and

S-waves by SKM channel. Calculation is by following formula:

MLV=lg(Az(Rg)/T) + σ2 (Δ), where 2()- calibration function for vertical component of maximal phase of surface waves; Az(Rg) – amplitude of

shifts on Z-component. Т – period, corresponding to Az(Rg), in seconds.

Some explosions were recorded by one Semipalatinsk station only by SKD instrument; for these explosions the accuracy of focal time

determination is much lower than for those recorded by the network of high-sensitive stations. In addition, Semipalatinsk station has low scanning

rate (Table 1), amplitude-frequency characteristic of SKD instrument does not allow to measure amplitude for calculating mpv magnitude and K.

Figure 13 shows energy class dependences on explosion yield, mpv on explosion yield, and MLV on mpv for air explosions.

Figure 12. The précised locations of air (P3) and surface (P5

and P7) nuclear explosions within Opytnoye Polye site.

N latitude longitude date origin time N mpv MLV К Y, Кт min Y max Y HOB 1 50.4227 77.7231 9/01/1961 07:01:53.0 6 3.2 2.7 7.9 16 660 2 50.4227 77.7231 9/13/1961 05:01:55.8 8 3 2.7 8.1 0.001 20 710 3 50.4227 77.7231 9/17/1961 07:00:46.6 8 3.2 2.8 8.5 20 150 695 4 50.3782 77.8373 9/19/1961 18:32:01.4 8 3.1 2.6 8.2 0.03 0 5 50.4227 77.7231 9/21/1961 14:01:00.0 5 3 2.2 7.7 0.8 110 6 50.4227 77.7231 9/26/1961 7:00:22.7 3 2.8 2.4 7.4 1.2 665 7 50.4227 77.7231 10/04/1961 7:01:20.8 8 3 2.7 8.4 13 605 8 50.4227 77.7231 11/01/1961 9:59:54.6 4 2.8 2.3 7.7 2.7 475 9 50.4123 77.7755 11/03/1961 9:00:37.5 1 1.9 0.9 635 10 50.4227 77.7231 8/03/1962 6:01:24.5 5 2.4 2.5 7.5 1.6 180 11 50.4227 77.7231 8/04/1962 3:00:57.0 7 2.7 2.5 7.9 3.8 390 12 50.4578 77.7655 8/07/1962 13:03:08.7 13 3.6 2.8 9.1 9.9 0 13 50.4227 77.7231 8/18/1962 5:00:24.9 5 2.9 2.8 8.2 5.8 310 14 50.4227 77.7231 8/18/1962 14:00:52.0 8 3 2.7 8.3 7.4 710 15 50.4227 77.7231 8/21/1962 12:01:09.1 13 3.3 2.8 8.9 20 150 590 16 50.4227 77.7231 8/22/1962 10:59:43.5 3 2.8 2.4 7.4 3 740

17 50.4227 77.7231 8/23/1962 11:00:28.1 5 2.6 2.5 7.6 2.5 680 18 50.4227 77.7231 8/25/1962 5:00:22.4 5 2.7 2.7 8.1 0.001 20 715 19 50.4227 77.7231 8/27/1962 13:01:34.6 11 3.4 2.8 8.8 11 245 20 50.4227 77.7231 8/31/1962 9:00:31.8 7 2.8 2.6 7.8 2.7 700 21 50.4502 77.7568 9/25/1962 3:30:50.8 11 3.6 3 8.9 0.001 20 0 22 50.4227 77.7231 9/28/1962 6:00:37.7 2 2.8 7.6 1.3 695 23 50.4227 77.7231 10/09/1962 6:00:43.0 10 3 2.7 8.2 8 645 24 50.4227 77.7231 10/10/1962 6:00:35.9 10 3.1 2.7 8.4 9.2 665 25 50.4227 77.7231 10/13/1962 9:00:17.5 1 2.8 4.9 720 26 50.4227 77.7231 10/14/1962 7:00:57.9 1 2.8 0.001 20 725 27 50.4227 77.7231 10/20/1962 9:21:45.6 6 3 2.6 8.1 6.7 635 28 50.4227 77.7231 10/28/1962 6:22:58 6 2.7 2.7 8.0 7.8 670 29 50.4227 77.7231 10/28/1962 16:59:33.3 9 3.0 2.6 8.4 7.8 645 30 50.4227 77.7231 10/30/1962 05:59:56.7 6 3.0 2.1 7.9 1.2 0 31 50.4227 77.7231 10/31/1962 05:00:07.2 7 2.8 2.8 8.5 10 690 32 50.4227 77.7231 11/01/1962 03:00:28 7 2.6 2.4 8.0 3 700 33 50.4227 77.7231 11/03/1962 09:00:11.8 10 2.9 2.5 8.2 4.7 710 34 50.4227 77.7231 11/04/1962 9:00:41.0 1 2.6 8.4 600 35 50.4227 77.7231 11/14/1962 11:32:15.6 12 2.8 8.7 12 660

36 50.4227 77.7231 11/17/1962 9:30:36.8 8 3.2 2.9 8.9 18 715

Table 2. The catalogue of air and surface explosions at the STS restored by historical seismograms.

1 10

7,2

7,4

7,6

7,8

8,0

8,2

8,4

8,6

8,8

9,0

Y, kt

K

Figure 13 а. Dependence of energy class K on

explosion yield for ANE.

1 10

2,4

2,6

2,8

3,0

3,2

3,4

Y, kt

mpv

Figure 13 b Dependence of mpv

magnitude on explosion yield for ANE

2,4 2,6 2,8 3,0 3,2 3,4

2,2

2,4

2,6

2,8

3,0

mpv

MLV

Figure 13 с. Dependence of MLV

magnitude on mpv for ANE.

Conclusion

Seismograms of air and surface nuclear explosions conducted at the STS in 1961 – 1962 were collected and digitized; the database includes 309

records from 24 seismic stations at distances 175-1480 km.

The records of air and surface explosions conducted at Opytnoye Polye of the STS have all signs of air explosions, strong surface waves, and

acoustic waves in some seismograms.

Parameters of 36 explosions (coordinates, t0, mpv, MLV, K) conducted at Opytnoye Polye of the STS in 1961 – 1962 were restored using

seismograms of air and surface explosions. The created catalogue can be used to solve different monitoring task.

References

1. Mikhailov, V.N. (editor) and 14 co-authors, (1996), USSR Nuclear Weapons Tests and Peaceful Nuclear explosions, 1949 through 1990,

RFNC-VNIIEF, Sarov, 96 p.

2. Khalturin, V.I., Rautian, T.G., and Richards, P.G. (2000), A study of small magnitude seismic events during 1961 – 1989 on and near the

Semipalatinsk Test Site, Kazakhstan, paper accepted for publication, Pure and Applied Geophysics, 2000.

3.Nersesov I.L., Rautian T.G. Kinematics and dynamics of seismic waves at distance up to 3500 km from epicenter // Experimental

seismics. Proceedings of IPE AS USSR. Science. Moscow. 1964. P. 63-87.

4. Aranovich Z.I. et al. Main types of seismometric instruments // Instruments and methods of seismometric observations in the USSR.

Moscow. Science, 1974. P. 43 – 117.

6.NXSCAN. Manual. IRIS, 1992.

7.J. Anderson, W.E. Farell [et al.] Center for seismic studies. Version 3 Database: Schema reference manual. // Technical Report C90-01,

Arlington. - 1990.

8.С. William, Tapley and Joseph E. Tull Seismic analysis cod // LLNL. - Livermore - 1993.

9. Mikhailova N.N., Aristova I.L., Germanova T.I. Travel-time curve of seismic waves following the results of signals recording from

chemical blasts // Geophysics and problems of non-proliferation. Vestnik NNC RK. 2002. Vol. 2(10). P. 46-54.

10. Mikhailova N.N., Neverova N.P. Calibration function for magnitude MPVA determination for Northern Tien Shan // Complex

researches in Alma-Ata prognostic site. – Alma-Ata: Nauka, 1983. P.41-47. (in Russian)

Parameters of 36 air and surface explosions were restored and supplemented using digitized historical seismograms. The restored catalogue of

air and contact explosions conducted at the STS is shown in Table 2.

As the stations were installed in the form of profile, there was no azimuthal surrounding of the STS, so it was not possible to determine the

coordinates with high accuracy using standard method. The coordinates of one of the targets of P3 site of Opytnoye Polye were selected as

coordinates of air explosions, and for surface explosions at P5 and P7 sites the coordinates of corresponding craters determined by space images

were selected (Figure 12).

To determine the explosions focal time the regional travel-time curve for Central Kazakhstan constructed using records of calibration chemical

explosions conducted at the STS in 1997 – 2000 and ground-truth underground nuclear explosions was applied [9]. To determine dynamic

parameters the regional mpv magnitude calculated by P-waves amplitudes for distances 10-1000 km was used. The curve of Mikhailova, Neverova

has been used in Kazakhstan since 1983 as regional calibration curve for mpv [10]. In addition, MLV magnitude and energy class K were

determined by surface waves [3].