| Abstract: | INTRODUCTION
The China Digital Seismograph Network (CDSN) is being designed and installed
to provide the People‘s Republic of China with the facilities needed to create
a national digital database for earthquake research. The CDSN, which is being
developed jointly by the PRC State Seismological Bureau and the U.S. Geological
Survey, will consist initially of nine digitally-recording seismograph stations, a data management system to be used for compiling network-day tapes, and a depot maintenance center. Data produced by the network will be shared with research scientists throughout the world.
A national seismograph network must be designed to support a variety of
research objectives. From this standpoint, the choices and tradeoffs involved
in specifying signal bandwidth, resolution, and dynamic range are the most important decisions in system design. As in the case of the CDSN, these decisions are made during the selection and design of the seismic sensor system and encoder components. The purpose of this report is to describe the CDSN sensor systems, their important signal characteristics, and the results of preliminary tests that have been performed on the instruments.
Four overlapping data bands will be recorded at each station: short period
(SP), broadband (BB), long period (LP), and very long period (VLP). Amplitude
response curves are illustrated in Figure I. Vertical and horizontal components
will be recorded for each data band. The SP and LP channels will be recorded
with sufficient sensitivities to resolve earth background noise at seismically
quiet sites. The BB channels will have a lower sensitivity and are intended
for broadband recording of moderate-to-large body-wave signals and for increasing the effective amplitude range in the short- and long-period bands. The VLP channel does not provide additional spectral coverage at long periods; its purpose is to make use of on-site filtration and decimation to reduce post
processing requirements for VLP studies. Early plans also included a triaxial
set of low-sensitivity accelerometers for recording strong signals from large
local and regional earthquakes. The accelerometers are not being installed;
however, they may be added in the future.
The short-period signals will be derived from a three-component set of
PRC-supplied Model DJ-I SP seismometers and US-supplied SP amplifiers. The
seismometers will be installed in surface or shallow subsurface vaults, except at two of the stations where they will be installed in boreholes. The BB, LP,
and VLP signals will be derived from Streckeisen STS-1 broadband sensor systems
installed in vaults, except at one site where the LP signals only will-be derived from a KS-36000 borehole seismometer installed at a depth of 100 meters.
Analog signals will be sampled and quantized by an analog-to-digital
converter (ADC) that is part of the recording system. Sampling rates chosen
for the CDSN are as follows:
* SP 40 samples/second
* BB 20 samples/second
* LP 1 sample/second
* VLP 6 samples/minute
The ADC 16-bit data word format makes use of 14 bits to quantize the signal and
2 bits to specify an automatically ranged gain of 1, 8, 32, or 128. This will
provide 84 dB of resolution and up to 42 dB of gain ranging for a total opera-
ting range of 126 dB peak to peak.
Magnetic tape cartridges, each having a capacity of 67 megabytes, will be
used for recording the digital data. LP and VLP data will be recorded continu-
ously. SP and BB data will be processed through an automatic signal detector
of the type described by Murdock and Hutt (1983), and only detected events will
be stored on tape. Detection parameters, such as turn-on sensitivity and mini-
mum recording duration for the SP and BB channels, will be fully programmable
and easily changed. One or more of the data channels may also be recorded on
analog recorders.
A CDSN recording system was not |
| Genre: | USGS Numbered Series |
| ProdID: | 15403 |
| Citation Author: | Peterson, Jon; Tilgner, Edwin E. |
| Citation Contributing Office: | USGS Albuquerque Seismological Laboratory |
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| Citation Edition: | - |
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| Citation Language: | ENGLISH |
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| Citation Online Only Flag: | |
| Citation Phsyical Description: | 63 p. |
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| Citation Public Comments: | |
| Citation Publisher: | Geological Survey (U.S.) |
| Citation Series: | Open-File Report |
| Citation Series Code: | OFR |
| Citation Series Number: | 85-288 |
| Citation Search Results Text: | Description and Preliminary Testing of the CDSN Seismic Sensor Systems; 1985; OFR; 85-288; Peterson, Jon; Tilgner, Edwin E. |
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| Citation Year: | 1985 |
| Type: | citation/reference |
| Text: | Description and Preliminary Testing of the CDSN Seismic Sensor Systems; 1985; OFR; 85-288; Peterson, Jon; Tilgner, Edwin E. |
| URL (THUMBNAIL): | http://pubs.usgs.gov/of/1985/0288/report-thumb.jpg |
| URL (DOCUMENT): | http://earthquake.usgs.gov/regional/asl/pubs/files/ofr85-288.pdf |
| URL (DOCUMENT): | http://pubs.usgs.gov/of/1985/0288/report.pdf |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
| Publisher: | Geological Survey (U.S.) |
