Advanced Waveform Research Methods for Geress Recordings

Abstract : The GERESS array project is a cooperative research program, jointly undertaken by Southern Methodist University Dallas (USA) and Ruhr-University Bochum in Germany. It is part of a multi-array network which includes NORESS, ARCESS, and FINESA in Scandinavia. This report summarizes research activities carried out at the data center in the Institute of Geophysics in Bochum during 1991. The GERESS array became fully operational in January 1991. Data are continuously transmitted from the array hub in Bavaria to NORSAR and to Bochum via 64 kbit lines. In Bochum, an experimental on-line processing system, based on RONAPP, is operated to monitor data quality and initiate necessary maintenance activities. Since July 1991, the on-site maintenance of the array is also overtaken by Ruhr-University as part of the research grant. The monthly uptime of the array varied between 88.4% and 99.7% with an average of 94.9%. At the data center in Bochum, an automatic event bulletin - interactively reviewed by an analyst - is produced and widely distributed to interested institutions. After one year of operation it is found that GERESS is the most sensitive station in Central Europe for monitoring local, regional, and teleseismic seismicity. During the GSETT-2 experiment, which was conducted by the Geneva experts group during the time period from April 22 to June 2 1991, GERESS located on average 16 regional events and detected 12 teleseismic events daily. Within the 6 weeks of GSETT-2, GERESS reported 3275 phases to the international data centers. Following a similar study at NORSAR, an evaluation of the P-wave detectability was undertaken for GERESS.