Seismic noise has been studied in a wide range of frequencies (more than 6 orders). The seismic noise density spectrum was compared with seismic noise models, obtained for observations of the Global Seismic Network (GSN IRIS). The arameters, characterizing variations of seismic noise from technological and natural sources were estimated.

Study of Dynamic Characteristics of Seismic Noise Basing on Data from Kazakhstan Network Digital Seismic Stations

Z.I. Sinyova, N.N. Mikhailova, I.I. Komarov

This paper shows the results of research on seismic noise characteristics for 8 Kazakhstan seismic stations. Spectral three component density curves were calculated, and the temporal variations of noise were studied for the whole range under investigation. It was found that the difference in the noise level from station to station depends on frequency. Maximum difference can be observed at the frequency of = 0Hz, when it reaches = 9db. At the frequencies of 0.2-0.05Hz statistically significant differences in the noise level were not observed. The following list of stations starts with the quietest station and ends with the noisiest one: Vostochnoe, Chkalovo, Zerenda, Borovoe, Kurchatov, Makanchi, Talgar, Aktubinsk.

Using Calibration Explosions at Semipalatinsk Test Site for Adjustment of Velocity Cross-Section of Earth Crust and Upper Mantle

N.N. Belyashova, V.I. Shatsilov, N.N. Mikhailova, I.I. Komarov, Z.I. Sinyova, A.V. Belyashov, M.N. Malakhova

The calibration explosions, conducted at former Semipalatinsk test site in = 997 and = 998, with charge of 25 tons and = 00 tons, were recorded by a number of digital seismic stations, located in Kazakhstan at distances varying from 0 to 720 kilometers. The recorded seismograms were used for creation of travel time curves and generalized one dimensional velocity models of the crust and upper mantle of the platform region of Kazakhstan . The travel time tables were obtained for the P, Pn, Pg, S, Sn, Lg phases for a distance range from 0 to 740 kilometers , and velocity model of the Earth's crust to the depth 44 kilometers and the mantle to the depth up to = 20 kilometers. A comparison of compiled hodograph with existing CSE and IASPEI-9 = hodopraphs was made.

Indian and Pakistani Underground Nuclear Explosions of 1998, Basing on Data from Kazakhstan Seismic Observation Network

N.N. Mikhailova, I.I. Komarov, Z.I. Sinyova

The analysis of wave characteristics of Indian (May11, 1998) and Pakistani (May, 28 1998) nuclear explosions records was made, using digital data from seismic stations, located in Kazakhstan (total number of 8 stations) at distances from = 6 o to 26 o from the source of explosions; kinematics and dynamical characteristics of P n and S n phases, as well as azimuths from stations to epicenter were determined. The results of location of explosion epicenter, using data from Kazakhstan stations only, and also from Kazakhstan stations together with Pakistani NIL seismic station, differ by 7 . = 2 kilometers for Indian explosion, and on 22 . 25 kilometers for the first Pakistani explosions from location results, given in REB and USGS catalogues. m b magnitudes determined from Kazakhstan data, were equal to 5,0 for Indian explosion, an 4,6 for Pakistani explosion of May, 28 = 998

Discrimination between Nuclear Explosions and Earthquakes at Regional Distances for Lop Nor Test Site

Yu. F. Kopnichev, O.M. Shepelev, I.N. Sokolova

This paper shows the results of research on discrimination between nuclear explosions at Lop Nor test site, which is situated in the North Western part of China, and nearby earthquakes. The amplitude ratios Pg/Pn, Sn/Pn, Sm/Pn, Lg/Pn and coda amplitude to Pn ratios were used according to the records from the stations, located on the territory of Kazakhstan . The most effective for discrimination frequency ranges were estimated for each station basing on these relations. They differ significantly from station to station.

2001

KAZAKHSTAN CENTER FOR ACQUISITION AND PROCESSING OF SPECIAL SEISMIC INFORMATION: FUNCTION, GOALS, TELECOMMUNICATION SYSTEM, DATABASES

N.N. Mikhailova, I.I. Komarov, Z.I.Sinyova, I.N.Sokolova

The paper summarizes the information about the basic functions of the Seismic Data Center IGR NNC RK, created in 1999. It describes the techniques of data acquisition, processing, and storage, and lists the main databases being created in the Center.

A STUDY ON THE SELECTION OF THE SITES FOR NEW SEISMIC ARRAYS IN KAZAKHSTAN

A.I. Nedelkov

The paper describes the research conducted at the sites selected for the establishment of new IMS seismic arrays according to CTBT. The seismic arrays PS023 (Makanchi) and AS057 (Borovoye) have been taken as the examples for demonstrating how a complete survey is conducted. The article shows the research results - array configurations and exact locations of the array elements.

THE JUSTIFICATION OF "BOROBOYE" NEW SEISMIC ARRAY ON THE BASE OF CORRELATION ANALYSIS OF SEISMIC DATA

Z.I. Sineva,Yu. O. Starovoit, N.N. Mikhailova

This paper discusses the investigative results of the spatial correlation of seismic signals and noise on the site selected for the new AS057-Borovoye seismic array. Several configurations of seismic arrays were examined and the possible signal increase for each configuration was estimated. As a result, the optimal configuration of the seismic array that provides the most effectiveness in the location of seismic events was determined.

ESTIMATION OF ENERGY AND MAGNITUDE CHARACTERISTICS BASING ON THE SEISMIC RECORDS OF CHEMICAL EXPLOSIONS OF 1997-2000 DETONATED ON THE FORMER SEMIPALATINSK TEST SITE

N.N. Mikhailova, T.I. Germanova, I.L. Aristova

The values of Energy class K and MPV magnitude were calculated for 15 chemical explosions conducted in 1997 � 2000 on the former Semipalatinsk Test Site. It was estimated that at one and the same yield energy characteristics can vary significantly depending on the depth of burial, medium around the explosion and other factors.

A STUDY OF SEIMIC DISCRIMINATION BETWEEN UNDERGROUND NUCLEAR EXPLOSIONS AND EARTHQUAKES AT INDIAN AND PAKISTAN TEST SITES

Yu.F. Kopnichev, O.M. Shepelev., I.N. Sokolova

Using data from Talgar seismic station located in the Northern Tien-Shan, we have studied the structure of shortperiod seismic fields for underground nuclear explosions (conducted at Pokharan and Chagai Hills test sites) and earthquakes with epicenters close to these test sites. The records of 37 seismic events with the magnitudes between 4.1 and 5.9 and epicenters 1600�2290 km away from the station have been studied. Amplitude ratios have been analyzed for different phases of longitudinal and shear waves and narrow-band filters with the central frequencies of 0.3, 0.6, 1.25, and 2.5 Hz. The optimal parameters have been determined for each test site, thus allowing the most effective discrimination between explosions and earthquakes.

2002

GEOPHYSICAL MONITORING SYSTEM CREATED IN NATIONAL NUCLEAR CENTER OF REPUBLIC OF KAZAKHSTAN AND ITS CAPABILITIES

Sh.T. Tukhvatulin, L.N. Tihomirov, N.N. Belyashova, N.N. Mikhailova, V.N. Demin, V.G. Marchenko, I.I. Komarov

Modern system of seismic and infrasound stations to control nuclear tests and earthquakes was created during last years as a part of National Nuclear Center of Republic of Kazakhstan . Some of these stations are included in International Monitoring System created by Comprehensive Test Ban Treaty Organization while others are included in global networks of seismic monitoring. Data Center in Almaty collects, process, stores, and exchanges these stations' data with international and other national data centers. Monitoring results are used for solving different practical and scientific research tasks.

NEW SEISMIC ARRAY KARATAU IN KAZAKHSTAN

V.G. Marchenko, A.I. Nedelkov, I.I. Komarov

Works on construction and putting in operation of new seismic array Karatau , Kazakhstan have been completed during 2001-2002. The paper shortly describes the array characteristic and its communications organization with the Data Centers.

NEW INFRASOUND STATION IS31 AKTYUBINSK OF THE CTBT INTERNATIONAL MONITORING SYSTEM

V.N. Demin, V.G. Kunakov, A.A. Smirnov

In compliance with the CTBT, the International Monitoring System is established. The infrasound station, recently constructed nearby Aktyubinsk City , is an element of this system. The construction of the station, examples of signals recorded by it are given in the article.

COMPARISON OF OMEGA-2 AND OMEGA-3 CALIBRATION EXPLOSIONS BASING ON REGIONAL SEISMIC DATA

N.N. Mikhailova, I.N. Sokolova

Comparison of different parameters of seismic records of Omega-2 and Omega-3 calibration explosions was performed. It was shown that despite the equal charge the level of seismic oscillations was lower during the Omega-3 explosion than during Omega-2. Spectral composition, polarization of oscillations, wave picture is identical at a given station for both explosions. Assumptions were made on the reason of such difference in seismic effect.

SEISMIC WAVES TRAVEL-TIME CURVE, BASING ON THE RESULTS OF SIGNAL DETECTIONFROM CHEMICAL EXPLOSIONS DETONATED AT SEMIPALATINSK TEST SITE

N.N. Mikhailova, I.L. Aristova, T.I. Germanova

A large amount of digital seismic data from the permanent and temporary seismic stations was acquired in the result of detonation of large chemical explosions at Semipalatinsk Test Site. All the records were collected, systematized and processed, and databases were created. Travel-time curves for regional Pn, Pg, Sn and Lg waves were created and compared with the ones used in routine earthquake processing practice.

THE NNC RK SEISMIC STATIONS DATA PROCESSING

N.N. Mikhailova, Z.I. Sinyova

In 2001, the IGR NNC Center for Special Seismic Information Acquisition and Processing developed and realized the processing technology of the seismic data entering in real time operational mode, in various modes of efficacy: for urgent reports service, for automatic seismological bulletin compiling, and for on-line seismological bulletin. As existing program packages so written and tested new programs are used and adapted.

SHALGINSK EARTHQUAKE IN CENTRAL KAZAKHSTAN OF AUGUST 22, 2001

N. N. Mikhailova, A.I. Nedelkov, I.N. Sokolova, E. N. Kazakov, A.V. Belyashov

The results of study of earthquake, which occurred in Central Kazakhstan on August 22 2001 in the region which traditionally was considered to be aseismic, are presented in the paper. Instrumental and macroseismic hypocenter parameters and a catalog of aftershocks are given. Geological and tectonic description of the earthquake epicentral region is shown. The conclusions were made about the actual accuracy of epicenter coordinates estimates by different data processing centers.

2003

DISCRIMINATION OF SEISMIC SOURCES LOCATED ON THE TERRITORY OF THE SEMIPALATINSK TEST SITE USING NNC RK SEISMIC STATION DATA

I.N. Sokolova, A.K. Mussin, G.S. Sultanova

The work shows the results of research on discrimination of chemical and nuclear explosions and near earthquakes at the Semipalatinsk Test Site. The records for the period between 1964 and 2002 recorded by the NNC RK Kurchatov, Makanchi, Borovoye and Talgar seismic stations located at regional distances from the test site were used. The spectral amplitude ratios were studied: Lg/Pg, Sn/Pg, Sn/Pn, Lg/Pn. A detailed analysis of time-frequency fields was performed in order to reveal the most effective discrimination criteria.

STUDY OF SHEAR WAVE ATTENUATION FIELD VARIATIONS IN CENTRAL ASIA REGION USING RECORDS OF NUCLEAR AND CHEMICAL EXPLOSIONS AT THE SEMIPALATINSK TEST SITE

Yu.F. Kopnichev, I.N. Sokolova

The temporal variations of amplitude ratio of Lg and Pg, Lg and P waves were studied using the 1964-2000 records of more than 200 underground nuclear and chemical calibration explosions obtained at the Northern Tien Shan TLG station, KURK station (Eastern Kazakhstan), BRVK (Kokchetav Massif), GRM ( Southern Tien Shan ) located at picentral distances of 77- 1400 km . Variations in this parameter with time are shown to be significantly different for different paths. The spatio-temporal variations of the seismic wave attenuation field are presumably associated with the ascent of juvenile fluids through large deep faults.

SEISMICITY OF REGIONS SURROUNDING THE NEW SEISMIC ARRAYS OF MAKANCHI AND KARATAU

N.N. Mikhailova, N.A. Volf, Z.I. Sinyeva

Upon putting into operation two seismic stations Makanchi and Karatau of world importance, appeared an opportunity to study seismic conditions of eastern and southern Kazakhstan at the energy level of events 3-4 orders below than it was earlier. Using weak and micro earthquakes, the accurate tracing of active lineaments and tracking of parameter variations of territorial seismic activity became more possible. The results have an important significance for solving tasks associated with estimation of seismic danger and development of the new seismic zoning plans of the Kazakhstan territory.

ABOUT MECHANISMS OF EARTHQUAKE FOCUSES OF CENTRAL KAZAKHSTAN

N.N, Mikhailova, N.N. Poleshko

In [2-4] first information about earthquakes in so-called "aseismatic" regions of Kazakhstan obtained by the IGR NNC RK specialists were published. Until recently central Kazakhstan was not in part of seismically active regions of Republic. With putting into operation the NNC RK station network, a number of earthquakes with magnitude up to 5,0 were registered. In the present work focus mechanisms for two seismically active zones of central Kazakhstan were determined for the first time. Mode of deformation characteristics of this region which compared with seismotectonic deformation parameters of Northern Tien-Shan and Djungary were established. Obtained results are very important for understanding the geodynamic processes on vast territory of Central Asia .

2004

A NEW SEISMIC ARRAY AKBULAK: CHOICE OF LOCATION, EQUIPMENT, COMMUNICATION SYSTEM

L. Teynor, R. Kemerait,K. Adair, N.N. Belyashova, V.G. Marchenko, A.I. Nedelkov, I.I. Komarov, A.V. Kunakov

Within the period of 2002- 2003 a series of works on construction and commissioning of a new seismic array �Akbulak� at the territory of the Western Kazakhstan had been conducted. The paper contains brief physical geographical and geological data and characteristics of the array (configuration, equipment, and system of communication with Data Center ).

ON EFFECTIVENESS OF PS23-MAKANCHI SEISMIC ARRAY IN REGISTRATION OF REGIONAL AND TELESEISMIC EVENTS

N.N. Mikhailova, Z.I. Sinyova

The effectiveness of PS23-Makanchi seismic array for registration of regional and teleseismic events was studied. To solve this task the different approaches were applied: compilation of the minimal magnitudes maps, plotting of seismic sensitivity curves, the plotting of recurrence graphs of seismic events with various magnitudes. After that the representative magnitude levels for different regions were estimated. It was concluded, that PS23-Makanchi array is rather efficient for both regional and teleseismic observations. The different values of D m parameter ( D m is a parameter that characterizes difference between minimal magnitude level of seismic events, recorded on given distance and representative magnitude level for the same distance) were observed on different distances. The diversity in the array sensitivity for events from different azimuths was revealed. This effect can be explained either by the difference in the seismic travel paths physical characteristics, or by peculiarities of the seismic observation network.

SPATIO-TEMPORAL VARIATIONS OF MACROSEISMIC EFFECTS FOR LARGE EARTHQUAKES IN THE REGIONS OF TIEN SHAN AND PAMIRS

Yu.F. Kopnichev, I.N. Sokolova

We analyze spatio-temporal variations of macroseismic effects using data for 32 large earthquakes (M �� 6.0) in the regions of Tien Shan and Pamirs occurred in 1885-1992. We consider the following parameters: average radius of intensity of 6 degree isoseist R ' 6 equal to magnitude of M=7.0, and also a ratio of average radius of intensities 4 and 6 isoseists (R 4 /R 6 ). A gradual diminishing of R ' 6 parameter values since the end of 1800-es to 1970-1975 is observed; these values increase rapidly since 1975. Besides, often value of R ' 6 decrease sharply after large close crustal earthquakes and deep-focus Hindu Kush events and R 6 /R 4 . We suggest an interpretation of the effects observed, which is connected with juvenile fluids ascending into the upper crust in source zones of large earthquakes and subsequent migration in horizontal direction. This leads to increasing the attenuation of strong motion amplitudes

PECULIARITIES OF GEODYNAMIC PROCESSES IN THE REGION OF CENTRAL TIEN SHAN : DETERMINATION OF ANOMALY REGION USING SEISMIC DATA

Yu.F. Kopnichev, N.N. Mikhailova, I.N. Sokolova

We conduct an analysis of seismic data for the Central Tien Shan region on the base of qualitative model for large crustal earthquake preparation, which has been suggested earlier. We analyzE spatial variations of transverse wave absorb field structure in the earth's crust and upper mantle, and also peculiarities of seismic regime in the region under consideration. We developed an abnormal area to the south-east of Bishkek city, where enough strong earthquake (M>6.0) can occur in a few years. The other geological, geophysical and geochemical data agree with such a conclusion.

DISCRIMINATION OF UNDERGROUND NUCLEAR EXPLOSIONS AND EARTHQUAKES USING NNC RK SEISMIC NETWORK DATA AT REGIONAL DISTANCES.

I.N. Sokolova

The structure of short period seismic waves field from underground nuclear explosions, conducted at the Lop Nor, Pokharan and Chagai test sites and earthquakes with epicenters near these test sites was studied for NNC RK stations. Threshold values and coefficients of discrimination quality were defined for each parameter.