Variation of Geomagnetic Vector in 10^5 to 10^6 Years

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1. Study of vector variation of the magnetic field based on Icelandic samples.We measured the paleomagnetic directions of about 150 lava flows from two vertical sequences (LT and SI) collected near Storutjarnir, northern Iceland. K-Ar ages were obtained for about 20 samples in these flows. The results indicate that these lavas erupted in the time interval of 2 to 3 Ma ago. We collected paleomagnetic and age date from published materials and formed a database containing the information of about 6000 lavas. Some results of analysis of the database will be presented at the society meeting in March 1996.2. Formation of paleointensity database and statistical analysis.We formed a paleointensity database by compiling published materials, and made it open to the public. We have done some statistical treatment of these data to see the characteristics of variation of magnetic field intensity (Tanaka, Uchimura, and Kono, Geophys.J.Int., 120,97,1995).3. A new model of paleosecular variation (PSV)We developed a new model of PSV based on the assumption that the Gauss coefficients of the geomagnetic field can be treated as independent random variables in sufficiently long time. Kono and Tanaka (J.Geomag.Geoelectr., 47,115,1995) applied this analysis to the scatter of virtual geomagnetic poles (VGPs), while Kono and Hiroi (Earth Planet.Sci.Lett., in press, 1996) used the same method to analyze the paleointensity data. Results indicate that g^1_) (orh^1_) is much larger than other nondipole terms which decrease exponentially with the degree of the harmonic.