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Jan Mayen, a geophysical laboratory

Jan Mayen, a geophysical laboratory. Jens Havskov. Jan Mayen location. Beerenberg. Facts about Jan Mayen. Norwegian island located 950 km West of Norway 55 km long Volcanic origin with an age of 0.7 mill years An active volcano Beerenberg (2277 m), the northernmost in the world

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Jan Mayen, a geophysical laboratory

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  1. Jan Mayen, a geophysical laboratory Jens Havskov

  2. Jan Mayen location

  3. Beerenberg

  4. Facts about Jan Mayen • Norwegian island located 950 km West of Norway • 55 km long • Volcanic origin with an age of 0.7 mill years • An active volcano Beerenberg (2277 m), the northernmost in the world • Inhabited with 18 persons running Loran C, meteorological station and infrastructure

  5. Topography & Bathymetry map of Scandinavia Topography

  6. Age map Age Map of Ocean Basins(Müller et al., 1997)

  7. Tectonics of North Atlantic Depth contours are at 1000 and 2000 m. Figure from Byrkjeland et al (2000) Jan Mayen island is situated between the two main spreading ridges along the North Atlantic, the Kolbeinsey ridge to the south and the Mohns ridge to the north. Spreading along these two main ridge systems is slow at a rate of 15-17 mm/year. Jan Mayen is also at the northern end of the Jan Mayen fracture zone, possibly a micro-continent.

  8. Tectonics of Jan Mayen The two mid-oceanic ridges are offset laterally by the Jan Mayen Fracture Zone (JMFZ), which approximately passes through the northernmost tip of the island.

  9. Focal mechanisms

  10. Jan Mayen eruptions Recent eruptions are shown with year of eruption and the new land generated (hatched)

  11. Jan Mayen eruptions

  12. Known eruptions

  13. Beerenberg and Eggøya

  14. Eggøya

  15. Dead craters

  16. 1970 eruption 1970 eruption began on September 18 and continued to January, 1971. Intense storms hid the onset of the eruption. A commercial pilot spotted the eruption cloud on September 20. It was the only historic eruption witnessed in modern times. The eruption was large, erupting at least 0.5 cubic km of basalt from a 6 km long fissure that ran from sea-level to an elevation of 1,000 m. There were at least five active craters.

  17. 1970 eruption

  18. 1985 eruption Earthquakes during 1985 eruption The 1985 eruption began on January 6, 1985 and lasted only 35-40 hours. 7 million cubic meters of lava was erupted . Earthquakes, with magnitudes up to 5, occurred during the eruption. The eruption was thought to be from a leaky fracture zone, not the Jan Mayen magma system

  19. Seismogram of 1985 eruption

  20. Earthquakes 1900-2000 Earthquakes are located by the Norwegian National Seismic network

  21. Norwegian National Seismic Network Seismic stations in Norway. Blue symbols are stations in Norwegian National Seismic Network, and red symbols are NORSAR arrays. Station JMIC is a CTBTO station operated by NORSAR Jan Mayen stations

  22. Seismic stations on Jan Mayen UiB has operated seismic stations on Jan Mayen since 1962 One station from 1962-70 Three station network 1971-present Additional broad band station since 1995, closed 2004 and replaced by a CTBTO station operated by NORSAR

  23. Seismicity of Jan Mayen Earthquakes located by Jan Mayen seismic network in the period 1982-2004. Only the best located events are shown (error in location < 20 km), in total 1148 quakes

  24. Statistics Number of located events near Jan Mayen, 1982-2004

  25. 2004, April 16, Mw = 6 earthquake a) The dots are earthquakes with magnitude 4 or larger recorded by ISC in the time period 1990-1999. The black box outlines the area in Figure b. b) The April 14, 2004 event located as determined in this study (BER) and by USGS (PDE). Mb=5.8, Ms=5.6, Mw=6.0

  26. 1988 event The 1988 event had Mb=5.6 and Ms=5.6, which is nearly the same magnitudes as the 2004 event 2004 and 1988 events are located in same area (accuracy 1-2 km) Largest known event in area is Ms=6.5 in 1923 Size of fault could generate M=7.5 events

  27. Aftershocks The blue dots are aftershocks occurring within 12 hours after the main shock; the red dots are later aftershocks occurring within 2 months after the main shock. The box outlines the extent of the ruptured fault plane from the aftershock distribution. A and B mark the two clusters of events within the Jan Mayen Platform, which are expected to occur on normal faults.

  28. Future ?

  29. Loran C Will be closed Jan. 1, 2006 Loran-C is a low frequency hyperbolic radionavigation and time reference system which provide a precise regional position service. The system uses stable 100KHz groundwave transmissions. Loran-C transmissions are also used for sending satellite positioning differential corrections (D.GPS) and several other services to users over a wide area. Eurofix provide excellent D.GPS data (often near 1 meter accuracy).

  30. Main station, continue

  31. Meteorology Will continue

  32. Research Geophysical observations Research observatory Seismic station North Jan

  33. Sun on Eggøya

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