SEISNET Seismic Network Data Collection presented at the WORKSHOP

1. SEISNET Seismic Network Data Collection presented at the WORKSHOP High Quality Seismic Stations and Networks for Small Budgets  Volcan, Panama 8-13. March 2004 by Jens Havskov, Department of Earth Science University of Bergen Norway

2. Main goal of SEISNET Automatically collect data from seismic stations to a central SEISAN data base using normally available communication channels

3. A physical seismic network. The sensors are connected to a central recorder through a permanent physical connection like a wire or radio link. In this example, transmission is analog and digitization takes place centrally, but the analog to digital converter could also have been placed with the sensor and transmission would then be digital.

4. A virtual seismic network. The thick line is the communication network, which can have many physical solutions. The data collection computer can collect data from some or all of the recorders connected to the network provided that it knows the protocol used by the recorder.

5. Seismic networks, 2 types: Physical seismic network: Closely linked remote seismic stations The remote stations detect the ground motion send data in real time to a central recording station for event detection and recording. Virtual seismic network: Consists of stations selected among many stations connected to the global communication network or a public phone system. The remote stations must be capable of event detection and local recording and data is normally not sent to a central recording system in real time.

6. Typical virtual data logger. The field station (right) has a ring buffer with files or segments 10 min long. It also has a list of detection times with associated parameters (det 1, det 2, etc) and corresponding waveform files (wav 1, wav 2, etc). The virtual data logger (left) has the following logging process: First get a copy of the detection times from all stations (det stat 1, det stat 2, etc, ... indicate a longer time window), which are time ordered. Based on these, network detections are made if at least 2 detections occur within a short time window (net det 1 and net det 2). Finally, the waveform files are copied. In this example, the ring buffer is not used

7. SEISNET capabilities Network operation: Retrieval of parametric information from seismic nodes Network event detection Retrieval of waveform data from seismic nodes Processing: Automatic phase identification, hypocenter location and magnitude determination Transfer of waveform data for a given hypocenter location and origin time

8. How SEISNET works

9. How SEISNET works

10. Types of nodes in SEISNET

11. SEISNET normally operates in the background started as a cron job Manual operation of SEISNET give various options:

12. SEISNET written in Expect and Fortran Runs on Sun and Linux Must have SEISAN installed Collects data to a SEISAN data base

13. Different ways of getting a TCP/IP connection to a central data collection system. The thick solid lines indicate permanent Ethernet connections.

14. Communication to GSN stations 2001. VSAT is satellite connection. VSAT and Internet have real-time connections and potentially all data can be downloaded, while the dial up stations on transmit a limited amount on data. (Figure from IRIS home page.)