ACOUSTIC WAVES FROM ATMOSPHERIC NUCLEAR EXPLOSIONS RECORDED BY INFRASOUND

AND SEISMIC STATIONS OF KAZAKHSTAN

(T2.3-P3)

Inna Sokolova

Institute of Geophysical Research AEC ME RK, Almaty, Kazakhstan

,

Availability of the acoustic wave on the record of microbarograph is one of discriminate signs of atmospheric nuclear explosions. Nowadays

there is large number of air wave records from chemical explosions recorded by the IMS infrasound stations installed during recent decade.

But there is small number of air wave records from nuclear explosions as air and contact nuclear explosions had been conducted since 1945

to 1962, before the Limited Test Ban Treaty was signed in 1963 (the treaty banning nuclear weapon tests in the atmosphere, in outer space

and under water) by the Great Britain, USSR and USA. First infrasound stations in the USSR appeared in 1954, and by the moment of the

USSR collapse the network consisted of 25 infrasound stations, 3 of which were located on Kazakhstan territory - in Kurchatov (East

Kazakhstan), in Borovoye Observatory (North Kazakhstan) [1] and Talgar Observatory (Northern Tien Shan).

Beginning from 2005 the IGR RK conducts work on scanning and digitizing of nuclear explosions seismograms, records of calibration

chemical explosions and earthquakes from Test Sites areas, and large Central Asia earthquakes (with M>5.5). Works on historical

seismograms digitization were conducted under methodical support of Lamont-Doherty Observatory (LDEO, USA), and under financial

support of Kazakhstan budget, LDEO, Norwegian Seismic Center NORSAR.

“NXSCAN” software which allows in semi-automated mode to digitize previously scanned seismograms was used. Fragments of

analogue seismograms digitized by NXSCAN [2] are saved in SAC format, and then converted into CSS 3.0 format. The testing results

showed that digitized seismograms have good concordance with original visually and by kinematic and dynamic parameters.

At the present time this database is used to solve different investigation tasks of seismology: precise parameters of historical large

earthquake and nuclear explosions; construction of regional travel-time curves of seismic waves; investigation of spatial-temporal variations

of attenuation field of shear waves; for tasks of seismic discrimination of nuclear explosions and earthquakes; for calibration of stations of

the International Monitoring System CTBTO; to study geodynamic processes and consequences of nuclear explosions influence on

environment.

Figure 1 shows an example of original and digitization results of atmospheric nuclear explosion seismogram 10/20/1962, t0=9:21:45.6,

=50.4227, =77.7231, mb=3.0. recorded by Mikhailovka station, epicentral distance was 333 km.

Figure 1.а) Analogue seismogram of air explosion recorded by

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

km.

Figure 1.b) Digitization result of seismogram of air explosion

recorded by Mikhailovka station on October 20, 1962, epicentral

distance is 333 km.

The seismograms from the archives of SEME MES RK in Almaty (Seismological Experience-Methodical Expedition), CSE IPE RAS in

Talgar (Complex Seismological Expedition of the Institute of Physics of the Earth Russian Academy of Science), IGR RK at seismic stations

Kurchatov, Borovoye, Aktyubinsk, Makanchi and IS KR in Bishkek (Institute of Seismology in Kyrgyzstan) have been digitized. Total number

of the digitized seismograms is 6845 seismic records (Fig. 2, 3). The records of atmosphere nuclear explosions recorded by standard

seismometers contain acoustic signals. In addition to seismograms, the archive of Complex Seismological Expedition contains microbarograph

records installed on the territory of Talgar Observatory; these also were scanned and digitized.

Figure 2. The map of nuclear explosions epicenters (stars) on

the territory of Eurasia, seismic stations (triangles), which

seismograms were digitized by the RSE IGR.

3074

717

1074

381

392

79 54 537

32 260 21 224 STS

Novaya Zemlya

PNE

Chemic

Nevada

In-Ekker

Pokharan

LopNor

Chagay

Mururoa

Amchitka

Earthquakes

Figure 3. The diagram of the digitized seismograms

distribution by the Test Sites and source type.

In 1960-s, a standard microbarograph with recording on photopaper that recorded several atmosphere nuclear explosions conducted at

Novaya Zemlya and Semipalatinsk Test Site had been installed on the territory of Talgar seismic observatory (Fig. 4, 5, 6).

Figure 4. Location of TLG station

and Novaya Zemlya and STS Test Sites

Figure 5. Design of

microbarograph sensor

Figure 6. Dependence of microbarograph sensor sensitivity

on oscillation period

The Novaya Zemlya Test Site is located in the Russian Federation on the territory of Novaya Zemlya archipelago being a

part of Archangelsk region. The archipelago consists of two large islands – northern and southern separated by Matochkin

Shar Strait (Fig. 7). 130 nuclear tests were conducted at Novaya Zemlya Test Site in 1955-1990, among them were: 88 air

explosions, 3 underwater explosions and 39 underground nuclear explosions. At zone A (the region of Chernaya inlet) there

were kiloton air nuclear explosions, underground nuclear explosions in shafts, and a surface nuclear explosion, 3 underwater

and 2 above-water nuclear explosions. At zone B the underground nuclear explosions were conducted in tunnels (mountainous

regions of Moiseyev and Lazarev). At zone C there were tests of multi-megaton nuclear charges thrown off the airplanes [3-8].

Figure 7. Boundaries of the testing subareas of the Novaya

Zemlya Test Site (NZTS). A, B, and C denote three main areas (zones)

of military activity: A = Guba (Bay) Chernaya. B = Guba

Mityushikha, south Bank of Matochkin Shar. C = Sukhoy Nos Cape

and its vicinity [3].

We found 19 records of acoustic signals from Novaya Zemlya Test Site at epicentral distance ~3600 km; the signals were recorded

by Talgar station (Fig. 4, 8); in some cases seismic record of atmosphere nuclear explosion was absent, there was only a record of

acoustic wave by microbarograph. The microbarograph records were acquired and digitized.

For two explosions conducted on December 18 and December 20, 1962 the origin time absent in nuclear explosions catalogues was

calculated by infrasound signals. The range of explosions yield for which the acoustic signals were found was 8.3 kt – 25 Mt. The

signals are long-period, maximum period is 210 s, average propagation time to the station is ~3 h 11 min, the acoustic wave velocity is

vi= 313±4 m/s.

Figure 8. The microbarograph record of nuclear explosion of August 27, 1962, t0=09-00-50.9, =74.7, =50.3, height is 3000

m, yield Y=4200 kt, by TLG station, a) analog record, b) digitized record, c) spectrum.

Figures 9 a, b show dependences of maximum amplitudes on explosion yield and periods of acoustic signals of atmosphere nuclear

explosions by Talgar station; good correlation is observed. Thus, the investigation results of acoustic waves parameters from

atmosphere nuclear explosions can be used in current nuclear tests monitoring for different tasks such as detection, identification of a

source type and assessment of explosion yield.

Amax= -288,73+79,61*lg(Y), R=0.85

Tmax=-105.64+68.62(lg(Y), R=0.88

0 5000 10000 15000 20000 25000

0

50

100

150

200

250

Y, kt

A,mkbar

1000 10000

60

80

100

120

140

160

180

200

220

Y,kt

Tmax,s

Figure 9. Dependence of maximum amplitudes а) and periods b) acoustic signals of atmosphere nuclear explosions at the Novaya

Zemlya Test Site on explosion yield by Talgar station.

The works [9, 1] note that the peculiarity of seismic records of air and contact nuclear explosions recorded by standard long-period

seismometers (Ts≥20s) is availability of featured oscillations in seismograms which arrival time and form coincide with corresponding

records of microbarographs, especially at its initial part. The reason of nuclear explosions acoustic waves recording by a seismometer is

ground motion caused by change of ground surface load when air wave passes the seismometer installation place. 6 acoustic wave

records were found for air explosions in seismograms of Alma-Ata (AAA) and Talgar (TLG) stations (Fig.10).

Figure 10. Seismogram air nuclear explosion, of December, 24, 1962, t0=11:11:42.0, =76.600 N., =57.500 E,

Y=24 Mt by the station Talgar (TLG) at distance 3830 km.

Nuclear explosions had been conducted at the STS in 1949-1989, air explosions (86) and surface (30) were conducted at Opytnoye Polye site,

underground explosions (340) in boreholes at Balapan and Sary-Uzen sites, and in tunnels of Degelen site (Fig. 11) [4, 7, 10, 11].

Figure 11 a)

The map of the test

sites location at the

STS.

Figure 11 b) The

map of Opytnoye Polye

site.

We have processed 15 records of acoustic signals from Semipalatinsk Test Site at epicentral distance ~800 km; the signals were

recorded by Talgar station (Fig. 4). The microbarograph records were acquired and digitized (Fig. 12, 13).

Acoustic signals were found for the explosions yield 2.5-18 kt, HOB was 310-725 m [7]. The signals have maximum period 3-10 s,

average propagation time to the station is ~43 min 6 s, the acoustic wave velocity is vi= 311±3 m/s.

Figure 12. The microbarograph record of nuclear explosion of October

13, 1962, t0=09-00-17.5, =50.4227, =77.7231, height is 720 m, yield Y=4.9

kt, by TLG station, a) digitized record, b) spectrum.

10

0

20

40

60

80

100

120

140

Y,kt

A,mbar

10

2

3

4

5

6

7

8

Y,kt

T,s

Figure 13. Dependence of maximum amplitudes а) and

periods b) acoustic signals of atmosphere nuclear explosions

at the Semipalatinsk Test Site on explosion yield by Talgar

station.

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

[10].

The records of atmospheric nuclear explosions at Opytnoye Polye site of the STS have all features 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 14).

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

Chingyuzha (CHNG), Leninogorsk (LNGR) , Ust’-Kan (USTK), Kzyl-Agach (KAC) at epicentral distances 322-556 km (Figure 15).

50 records of acoustic wave were found and processed. The acoustic wave records (Figure 14b) 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 16). 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,

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 14 а) Seismograms of air

explosion of October 20, 1962, t0=09-21-

45.6, =50.4227, =77.7231, by station

NCE (328 km).

Figure 14 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).

Figure 15 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 16. Dependence of

amplitudes of air wave

record on air explosions

yield, MIKH station.

CONCLUSION

The IGR has created a database of digitized historical seismic and infrasound records of nuclear explosions.

2. Unique records of a microbarograph installed in 1960-s at Talgar Observatory near Almaty (Kazakhstan) were found.

The historical analog records of the microbarograph were analyzed on the availability of the acoustic wave, selected records were

digitized, the database of acoustic signals from nuclear explosions was created.

3. The peculiarities of the wave pattern and spectral content of the acoustic wave records, and relation regularities of acoustic wave

amplitude and periods with explosion yield were investigated.

4. The created database can be applied in different monitoring tasks, such as infrasound stations calibration, discrimination of

nuclear explosions, precision of nuclear explosions parameters, determination of the explosion yield etc.

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