# Notes on how this file is interpreted by the program "bul" # All lines starting with # are coment lines and not printed. # Lines starting with %xpos=0.12 or %ypos=2.5 will position the pen so that next line will # start to write from that postion. If no position is given the defualt is that the # pen will be positioned 0.25 inch lower on the page. # Lines starting with %center will cause centering of next line # All lines starting with %size=0.12 will be printed with 0.12 inches hight etc. # Default size is 0.15 inches # Lines starting with %Months will be print the months covered by the bulletin. # Lines starting with %Year will be print the months covered by the bulletin. # Blank lines will be written # All lines starting with '%Next Page' will cause page break. # All other lines will be printed as they appear # Lines starting with %font= will cause that the following strings are printed with # the given font number # Font index # 1 = Times-Roman # 2 = Times-Italic # 3 = Times-Bold # 4 = Helvetica # 5 = Helvetica-Oblique # 6 = Helvectica-Bold # 7 = Courier Must be used on tabular data !!!! # 8 = Courier-Oblique # 9 = Courier-Bold # # %size=0.5 %xpos=2.0 %ypos=9.0 %center %font=4 Seismological Bulletin %size=0.2 %xpos=4.0 %ypos=8.0 %center from the %size=0.40 %xpos=2.0 %ypos=7.0 %center Norwegian Seismic Network %size=0.3 %xpos=3.5 %ypos=5.5 %center %Months %size=0.25 %xpos=4.0 %ypos=4.5 %center %Year %size=0.15 %xpos=3.0 %ypos=3.0 Institute of Solid Earth Physics, University of Bergen Allegt. 41 5007 Bergen Norway Tel : +47-55-583420 Fax : +47-55-589669 E-Mail : seismo@ifjf.uib.no %Next Page %font=7 GENERAL BULLETIN INFORMATION The location program currently used for locating earthquakes is Hypocenter (Lienert et al.,1986). Plane parallel layers are assumed for local and regional events, while the IASPEI travel time tables are used for distant events. The model used for all local and regional events, except for the Arctic island Jan Mayen, is published by Havskov and Bungum (1987). P-wave velocity (km/sec) depth to top of layer (km) 6.2 0.0 6.6 12.0 7.1 23.0 8.05 31.0 8.25 50.0 8.5 80.0 Magnitudes are calculated from coda duration and/or amplitudes. The coda wave magnitude is estimated via the formula (Engell-Sorensen,personal communication): Mc = -3.0 + 2.6 * log10(T) +0.001 * D. where T is the coda duration (sec) and D is the epicentral distance (km). If instrument corrected maximum ground amplitudes A(nm) are available, local magnitude Ml is calculated by the following formula (Alsaker et al., 1991): Ml= 0.925*log(A) + 0.91*log(D) +0.00087*D -1.31 were D is the hypocentral distance (km). For the Jan Mayen area a local model is used (Sornes and Navrestad, 1975): P-wave velocity (km/sec) depth to layer (km) 3.14 0 6.33 3 8.27 18 The coda magnitude formula for Jan Mayen is given by Westre (1975): Mc = -3.24 + 3.27log10(T) + 0.001 * D All available amplitudes and coda values are used for magnitude calculations. No station corrections are used for either travel times or magnitudes calculations. The Vp/Vs velocity ratio used in both layered models above is 1.73. As a general policy, neither depths nor epicenters are fixed unless stated since this might restrict later use of the data. As a consequence, some event locations might be unrealistic like zero depth earthquakes around Jan Mayen or teleseismic locations off by 1000 km. However, the locations are based on the available data and reflect the location procedure and the models used. %Next Page %size=0.15 %font=7 STATIONS USED The stations listed below are those operated by the Institute of Solid Earth Physics, University of Bergen (UiB). However, readings from other cooperating agencies are also used in locating the events and calculating magnitudes and thus more stations will appear in the event lists than in the station list. The most common additional readings and magnitudes are received from NORSAR (Norwegian Seismic Array), and the stations and arrays operated by this agency are shown below. Data from NORSAR is included according to the following criterias: Also all NORSAR events recorded by UiB are included. In addition, events with magnitude larger than or equal to 2.0 and reported by NORSAR only, are included. STATION LATITUDE LONGITUDE HEIGHT(m) NAME -------------------------------------------------------- ASK 60.4830N 5.1950E 50 ASKØY BER 60.3683N 5.3340E 50 BERGEN BJO1 74.5060N 19.1880E 18 BJØRNØYA BLS5 59.4230N 6.4560E 540 BLÅSJØ EGD 60.2712N 5.2257E 20 ESPEGREND FOO 61.5980N 5.0440E 15 FLORØ HYA 61.1660N 6.1870E 30 HØYANGER JMI 70.9283N 8.7308W 211 JAN MAYEN JNE 70.9898N 8.2968W 57 JAN MAYEN EAST JNW 71.0287N 8.4282W 95 JAN MAYEN WEST KBS 78.9168N 11.9173E 46 KINGS BAY KMY 59.2120N 5.2470E 58 KARMØY KONO 59.6490N 9.5982E 216 KONGSBERG KTK1 69.0117N 23.2372E 340 KAUTOKEINO LOF 68.1325N 13.5410E 80 LOFOTEN MOL 62.5703N 7.5483E 98 MOLDE MOR8 66.2855N 14.7352E 445 MO I RANA NSS 64.5307N 11.9673E 102 NAMSOS ODD1 59.9120N 6.6280E 684 ODDA OSG 60.4967N 2.8758E -110 OSEBERG (OBS) RGS 63.0210N 10.4350E 410 ROGNES SUE 61.0570N 4.7610E 10 SULEN TRO 69.6330N 18.9280E 15 TROMSØ NORSAR ARRAYS APA0 67.61N 32.99E 200 APATITY, KOLA ARA0 69.53N 25.51E 353 ARCESS, FINNMARK NRA0 60.74N 11.54E 300 NORESS, HAMAR SPA0 78.18N 16.37E 323 SVAESS, SPITSBERGEN MACROSEISMIC DATA Macroseismic data, if available, are included in the bulletin. %Next Page %size=0.15 %font=7 Abbreviations: TIME: Origin time in UTC (hr. min. and sec.) or data file onset time if event is not located. LAT: Latitude of epicenter LON: Longitude of epicenter DEPTH: Focal depth in kilometer (trailing F indicates fixed depth) AGENCY: Hypocenter reporting agency e.g. BER (Bergen), NAO (Norsar) MAGNITUDES: Up to 3 different magnitudes can be given followed by type and and reporting agency, e.g. 3.1 MC BER - coda magnitude calculated in Bergen. RMS: Root mean square value of travel time residuals STAT: Station code CO: Component,S:short period,L:long period,B:broadband, DIST: Epicenter distance (km) AZI: Azimuth from source to station PHAS: Phase; The first letter characterizes onset E(mergent) or I(mpulsive) P: Polarity ( C for compression, D for dilatation ) HR: Hour MN: Minute SECON: Seconds TRES: Residual (seconds) CODA: Signal duration in seconds AMPL: Ground Amplitude (0.5*(peak to peak)), (nm) at period PERI PERI: Period where amplitude is measured BAZ: Back azimuth (station to event) ARES: Back azimuth residual VELO: Apparent phase velocity (km/sec) WT: Weight of phase in the location *: An asterix before the phase arrival time implies a potential timing error. If an S phase is read, differential S-P times will be used in the hypocenter location. References: Alsaker, A., Kvamme, L.B., Hansen, R.A., Dahle, A. and Bungum, H. (1991). The ML scale in Norway. Bull. Seism. Soc. Am., 81, pp. 379-398. Havskov, J. and Bungum, H. (1987). Source parameters for earthquakes in the northern North Sea, Norsk Geologisk Tidskrift. 67, pp.51-58. Lienert, B.R., Berg, E. and Frazer, L.N.(1986). Hypocenter: An earthquake location method using centered, scaled, and adaptively least squares. Bull. Seism. Soc. Am., 76., pp 771-783. Sornes, A. and Navrestad, T. (1975). Seismic survey of Jan Mayen. Norsk Polarinstitutt, Arbok 37-52, Norsk Polarinstitutt, Oslo, Norway. Westre, S. (1975). Richter's lokale magnitude og total signal varighet for lokale jordskjelv pa Jan Mayen. Cand. real thesis., Seismological Observatory, University of Bergen, Norway. %font=1 # Font 1 will be used in headers for the rest of the document