|Observatories and Research Facilities for EUropean Seismology|
|Volume 4, no 1||May 2002||Orfeus Newsletter|
Towards a Virtual European Broadband Seismograph NetworkT. van Eck1, C. Trabant1, A. Heinloo2, B. Dost1, R. Sleeman1, F. Goutbeek1, W. Hanka2, E. Carenno3, M. Tome de la Vega3, S. Mazza4, A. Mandiello4, M. Ollivieri4, G. Chouliaras5, N. Melis5, A. Deschamps6, W. Lenhardt7, N. Horn7, M. Baer8, J. Schweitzer9 M. Zivcic10, G. Mocnik10, K. Solomi11, J. Zednik12, J. Kivisilla13, G. ROult14, M. Granet15, K. Stammler16, A. Shapira17, M. Russi18, G. Costa19, P. Wiejacz20, E. Buforn21, A. Pazos22, M. Aktar23, D. Kalafat23
- initializing real-time data exchange within Europe
- enlarging the accessible European waveform data archive
One of the products within MEREDIAN is the Virtual European Broadband Seismograph Network (Figure 1). It deploys real-time standardized Internet data exchange procedures, among others SeedLink, and is coordinated within ORFEUS. Real-time data gathering by the Orfeus Data Center (ODC) is part of a broad initiative to automate its data archiving procedures. An assessment of nearly five months of operation show that the network can contribute significantly to an EMSC coordinated European rapid warning system.
Figure 1. The Virtual European Broadband Seismograph Network: the situation as of May 2002. Triangles are stations that provide or will provide real-time data to the network. This network is one of the products of the EC-project MEREDIAN. MEREDIAN-2 is a complementary EC-proposal that involves "candidate EU countries". The seismicity (all events M > 3.0) is taken from the NEIC catalogue.
ORFEUS Working Group 1 broadband station siting). The ODC is therefore restructuring and automating its data management and archiving procedures. The real-time data gathering plays an important role in ensuring rapid archiving, triggering automatic procedures and early data quality monitoring. For example, early locations of events in Europe and its immediate surroundings enables us to trigger rapidly automatic AutoDRM based gathering procedures for additional event data not available in real-time.
The data management structure presently being implemented at the ODC is shown in Figure 2. As a result more data becomes more rapidly available and additional real-time data products can be derived. In order to maintain homogeneity in the data products and data retrieval mechanisms as offered by the ODC the developments are closely co-ordinated with those at IRIS-DMC.
The continuous data will become available this summer through AutoDRM in GSE format from a seven-day buffer. Data from the event data pool, which eventually will replace Spyder®, will be made available during autumn 2002 through the usual access methods (Wilber(II), FTP, AutoDRM and NetDC).
Figure 2. Schematic view on the data management structure at the Orfeus Data Center. This figure puts emphasis on the real-time data collection procedures. It illustrates also the different data products which are, or will soon be made, available. In the future we envision that nearly all data collection procedures will be automatic, either real time or near real time.
Presently, data from nearly 40 stations are gathered, and around 20 more stations are planned to be added in the next 6 months. Automatic locations and magnitude determinations provide the basis of event selection for the Event Data Pool, containing SEED event volumes. The same event detections trigger automatic AutoDRM procedures to retrieve additional data from stations not available in real-time.
An assessment of nearly five months of operation (with around 24-35 stations) shows that both reliable and rapid locations are provided for events in Europe and its vicinity (see Figure 3), which compare favourably with both the NEIC and EMSC locations. Emails with rapid automatic location and picks are sent on request (contact MEREDIAN coordinator Torild van Eck).
A selection is made of medium to large size events in Europe and its vicinity as automatically reported by the ODC by email within about 15 minutes. This report includes location, Mb estimate and automatic picks. The locations will be used by the ODC to trigger event data collection from stations that are not available in real-time.
Figure 3d. An overview showing the delay time, i.e. the time between the event Origin Time and the reporting time by the VEBSN (location and first magnitude estimate), as compared with those of the NEIC, SED and EMSC.
Seismological Communication Processor (SeisComP) is an initiative of the GEOFON program at the GFZ, Potsdam, Germany (Hanka et al, 2000). It is a software package for data acquisition, recording and monitoring, real-time communication and automatic network data processing (data quality control and event detection/localization). SeisComP works presently under both Linux and Solaris. The data acquisition part is based on Quanterra's publicly available ComServ software. The real-time communication part (SeedLink) ensures robust transfer of miniSEED packages through any TCP/IP based communication channel - even poor quality ones - both in continuous and dial-up modes. Data Acquisition plugins for a large number of acquisition systems are presently available (see Figure 4) and more will be developed. Data export is supported through the SeedLink protocol to other SeisComP systems and Antelope®. The MEREDIAN project supports presently many of the SeisComP and plugin developments, which are coordinated within the SeisComP users group. The SeisComP, SeedLink and plugin software are all publicly available and protected under the GNU license.
Figure 4. Schematic view of the presently existing data input and export possibilities with SeedLink as developed by GFZ, ODC and others. Many of the data acquisition plugins are employed within the Virtual European Network. Developments can be followed on the MEREDIAN web pages.
IRIS DMC, the CTBTO - IMS and the UCSD and on a regional scale at NEIC for the US National Seismic Network (see Malone, 2002). However, using SeisComP, Antelope or EarthWorm each individual user can create his own network to satisfy his special needs. That e.g. provides very flexible inter-network or cross-border solutions for real-time data exchange. A condition, however, is the existance of an excellent communication infrastructure, i.e. Internet, satelite or telephone for example. Presently, in Europe, other successful similar project are running on a national scale in Germany and Italy and on a regional scale between networks in NE Italy, Austria and Slovenia. MEREDIAN is an EC-project under contract EVR1-CT-2000-40007. Below, the MEREDIAN consortium and the additional participating observatories are listed.
The actual web addresses of the institutes/observatories can be found on the Euro-Med Observatories