KNDC

The Kurchatov-Cross array is located in north-east part of the Republic of Kazakhstan, 145 km away from Semey town on the left bank of the Irtysh River. Terrain relief is mainly plain, absolute heights are 160 - 200 m . Created during Soviet time the "Cross" seismic array is located near Kurchatov town. The "Cross" orientation was selected with the aim to amplify seismic signals from small underground nuclear explosions conducted at Nevada Test Site (USA) as much as possible.

The "Cross" seismic array represents two linear lines (east-west, and north-south) of equipment boreholes of 22,5 km long each. Each line has 10 equipment boreholes (sites) with a central site at the place of lines intersection. Average distance between the sites is about 2,25 km .

North-south line (1-10 sites) has a trend azimuth of 10 0 NE, east-west line (11-20 sites) has a trend azimuth of 280 0 NW.

The "Cross" system is located in tectonic block consisted of sediments of Maytobinsk suite ( С 3 mt ). Maytobinsk suite is related to variegated volcanic-sedimentary formation of continental type with slow volcanic action. According to flora and freshwater fauna age the formation is related to late carboniferous period C3 (age C3 - late Carbon). Rocks: sandstones, siltstones, pudding rock, tuff, porphyrites.

Rocks characteristics by boreholes:

Borehole	Depth, m	Rock type
1	35,6	sandstone, rocky ground from 7m.
2	38,5	sandstones and siltstones, rocky ground from 5m
3	32	porphyrite, rocky ground from 17 m
4	38,87	tuff, rocky ground from 17 m
5	27,5	tuffaceous, rocky ground from 22,5m.
6	35	siltstone, rocky ground from 7 m
7	36,53	conglomerates (19- 36 m depth), gravelstone (36-41m), rocky ground from 19 m
8	39	silstone (10-41m depth), sandstone (41-45m), rocky ground from 10m
9	29,5	siltstone (7- 21 m ), sandstone (21- 31 m ), rocky ground from 7m
10	36,15	siltstone 7-21m, sandstones (21- 31 m ), rocky ground from 7m
11	30	tuffsandstone, rocky ground from 7 m
12	34,1	tuffsandstone, rocky ground from 3 m
13	44,4	siltstone, rocky ground from 24m
14	38,16	sandstones, rocky ground from 10 m
15	36	Mindalekamen porphyrite, rocky ground from 25m
16	32,7	tuff, rocky ground from 22,5 m
17	38,27	porphyrite and plagioclase pyroxene, rocky ground from 9,5 m
18	49,38	medium- and coarse-grained sandstones, rocky ground from 20 m
19	26,5	conglomerate, rocky ground from 12 m
20	50	Mindalekamen porphyrite, rocky ground from 5,5 m
21	52	sandstones, siltstone and clay rock, rocky ground from 46 m

Since 1973 at current "Cross" array place, so called "old system" had been operating. Its characteristics were not saved .

Array system was reconstructed in 1986- 1992. In 1994 "Kurchatov-Cross" array was put into operation. Short-period borehole seismometers K-213-C with 2 s free period were installed in each borehole at different depths. Transformation coefficient is 75000 v/m/sec, dynamic range - 80 dB. Signals of borehole seismometers were filtered with analog high- and low frequency filters with cut frequency 0,5 and 2,5 Hz.

Analog signals from sensors were digitized by 16-bit digitizers with frequency of 100 samples per second.

In October, 1994, 16-bit digitizer on personal computer base was installed in Central recording Facility at the second technical site of "Kurchatov" GO. Analog signals were digitized with 20 samples per second and were recorded constantly on 4 GB computer disk. Since January 1995, samples rate was increased up to 40 samples per second.

Characteristics of equipment boreholes:

According to Comprehensive Test-Ban Treaty signed by Kazakhstan in 1996, "Kurchatov-Cross" station is included into seismic monitoring network of the International Monitoring System as auxiliary station (AS 058). According to International Monitoring System station requirements, the station was modernized in 2006. Since July 26, 2006 this station has been operating in test mode as International Monitoring Station. On December 18, 2006 the station was certified by International committee as International Monitoring Station.

New equipment was installed in the same equipment vaults where the old system was. One component seismometers CMG - 3V are installed at 1-20 sites, and three-component seismometer CMG-3 ТВ at 21 site.

Europa -T of Nanometrics Company is a registration station. Digitization frequency is 40 samples per second. Timing is by GPS system.

Information acquisition to Central Recording Facility (CRF) and to data processing facility (TS2) is conducted by VIP 110-24 radio modems. Data obtained at the station are transferred from CRF to International Data Center in Vienna via satellite channel. Data are transferred from IDC ( Vienna ) to the Data Center in Almaty (KNDC) in real time.

About NNC RK Observation System.

Kurchatov Seismic array.