The GEOSCOPE Program
and Jean-Paul Montagner
The purpose of the GEOSCOPE program was the installation of about 20 stations well
distributed worldwide (in particular in the southern hemisphere), in the standard
configuration defined by the FDSN (VBB 24 bit, continuous recording at 20 samples/s).
The installation is almost complete. The effort has been focused on the accessibility
of data from our Data Center. Data can be obtained either on line through the
WWW server, or through our
anonymous ftp, or through CDROM production
or through the
system for large earthquakes. In the near future easier
ways will be available, such as autoDRM ( automatic Data Request Management) and
NetDC requests (protocol proposed by the IRIS DMC).
The Data Center of Paris is archiving data from 29 stations :
- twenty-six permanent « Geoscope » stations
- 20 Stations maintained by the Technical Division of IPGP (Saint-Maur, near Paris).
All of them are operating in VBB configuration (BH channel at 20 sps, LH channel
at 1 sps, VH channel at 0.1 sps).
- 4 stations maintained by EOST (Strasbourg), in VBB configuration.
- 2 stations maintained by ORSTOM in Africa in VH/LH/MH configuration (VH in m/s/s
with continuous recording at 0.1sps, LH in m/s/s with continuous recording at 1s
ps, MH in m/s and triggered at 5sps).
- three « contributing » Geoscope stations (in VBB configuration):
- 1 station maintained by ORSTOM and EOST in Vanuatu Islands, PVC.
- 1 station maintained by IPGP (Seismotectonic group) in Chile, ICC.
- 1 station maintained by Centro de Geofisica de Universidad de Lisboa (Portugal), EVO.
Sixteen stations are remotely accessible (teletransmitted by phone). In case of
large events, data from these stations are recovered in St Maur (Figure 1, green dots)
and made available at the Data Center in Paris within one or two days. In parallel to
the classical recording in station (VBB configuration), seismic data are continuously
recorded on a magneto-optical disk at 20sps. This method designed by the Technical
Division has been implemented since 1992 in twelve stations (Figure 1, red dots).
In all stations the time reference is given by a GPS clock. In the future, a satellite
transmission system will be installed in ten stations, in cooperation with the french
military agency CEA/DASE (see the white dots in Figure 1).
In terms of siting locations, the aim of the GEOSCOPE program is almost fulfilled;
we plan to install only one new station: Vorkouta with our colleagues of IIEPTMG.
After the installation of this last station, our goal is to install in each station,
a new acquisition chain defined by
(in Toulouse) and DT/IPGP in order to improve their quality.
The GEOSCOPE Data Center has been organized since 1992 around the master piece of the
Center, a juke-box of 300Gbytes. All incoming data are stored on the juke-box after time
corrections using comparisons between reference GPS clock and internal clock time, data quality
control and determination of the corresponding instrumental responses.
All recent earthquakes with magnitude greater than 6.3, or with smaller magnitude but with
particular scientific interest (location, focal depth, ...) are teletransmitted to the Data
Center at St Maur, from 17 stations. The corresponding data are made available at the Data
Center in Paris for two channels, the VH channel, the MH channel and for two stations
(HDC and KIP) the BH channel .
All GEOSCOPE existing data from the beginning of the network in 1982 up to now are available
from our juke-box.
Database is open to external users and data are easily available through :
CDROM for data spanning time from 1982 to 1991, are skipping by normal mail way.
The GEOSCOPE data are now worldwide well known, and the number of users and of requests is
increasing with time. Of course the procedure by anonymous ftp is more often used, with a
volume of 53 Gigabytes instead of 2 Gigabytes through the WWW server for the same period,
certainly because of the higher rapidity and of easier way in case of multiple requests by
the first procedure. GEOSCOPE data are also available in other Data Centers such as
IRIS DMC in Seattle
(continuous and event data from 1982 to 1996), and the
ODC Center (Orfeus) in the Netherlands (event data for
The challenge of the GEOSCOPE Data Center is to offer to the seismic community a performing
central data archiving system, to get a clear and easy distributed data request processing and to
provide new services management.
- The GEOSCOPE station book
On the WWW server the totality of the GEOSCOPE station-book is provided; it is updated as
soon as there is a modification. Each station is described since its beginning with information
about the parent organization, the network affiliation, the vault conditions, the site description, the
instrumentation, the sensors, the channels, the dates of upgrade, the sensitivities in the flat part of
the band-pass of the instrumental responses. You can find the curves of instrumental responses of
the stations, for each component, for each channel, each period of time since the beginning of the
- Continuous VBB (BH) channels
In parallel to the classical recording in a station (triggered BH channel), seimic data are also
continuously recorded on a magneto-optical disk at 20sps. This method, designed by the
Technical Division at Saint Maur in cooperation with the CEA/DASE is now implemented in
twelve stations allowing to be sure not to loose some data with the triggering system. The PVC
station located in the Pacific Ocean and maintained by our colleagues of EOST in Strasbourg and
ORSTOM in Nouméa (New Caledonia) also corresponds to a continuous recording of BH channel at
- The GEOSCOPE noise level plots
The estimate Power Spectral Density plots have been computed for year 1995. The annual seismic
noise level is presented for the 3 channels VH, LH and BH, for the 3 components, Vertical ,
North-South and East-West. The diurnal and seasonal seismic noise plots are presented for the 3
components, and respectively for both channels BH and LH (for the diurnal variation) and for the
three channels BH, LH and VH (for the seasonal variation).
The French SSB station recorded in Quasi real-time data
Data are received from the GEOSCOPE SSB station located in France at the Data Center in Paris
in quasi real-time. Every hour we get data for three 20 minutes length files, for the MH channel
(in fact the BH channel decimated at 5sps). The data are immediately and automatically stored on
a disk, and the corresponding plots available on the WWW server. The interest is to get
immediately and continuously data from the french station.
- GEOSCOPE CMT determination
A simple inversion method for the fundamental mode Rayleigh wave spectra has made possible
the rapid determination of the mechanism and the seismic moments. The demonstration is done
that a correct CMT can be retrieved by using few stations, and that in a laterally heterogeneous
- The NetDC procedure
The necessity for dissemination of large datasets to the seismic community leads to the need of a
new form of distribution with cooperative environment between the different participating data
centers. The NETDC (Networked Data Centers) idea (designed by IRIS in cooperation with other
Data Centers, GEOFON, ORFEUS, UC Berkeley) is to make the access to data transparent to
users, who should not bother about where to ask for data ; the routing of the data request should be
solved by the coordinating data centers. The INVENTORY protocol is already working in our
Data Center (firstname.lastname@example.org) and we will install the Instrumental responses as soon as
- The future with GEOSCOPE 2000
In the future all GEOSCOPE stations will be equipped with seismometers but also with POS
sensors, microthermometers, microbarometers, inclinometers, short period seismometers, GPS.
The new acquisition chain designed by DT/IPGP and the manufacturer AGECODAGIS in
Toulouse (France) will provide recordings from 22 channels, 6 main channels (24bit) for ground
velocity and POS measurements (recorded continuously at 20sps and triggered at 80sps for the
STS2 seismometer), and 16 auxiliary channels in 16bit (1,6s). In the framework of the Test Ban
Treaty, some GEOSCOPE stations have been chosen to be teletransmitted by satellite in real-time,
and ten stations will be equipped in that purpose with help of CEA/DASE. WUS station
equipment has been installed through a direct cooperation between GEOSCOPE and the SSB
(State Seismological Bureau) of Beijing in China. AIS station in the Indian Ocean has been
equipped during 1998 in the framework of the cooperation between IRIS and GEOSCOPE.