4:30 PM - 4:45 PM
[SEM34-19] Reexamination of geomagnetic secular variation in Kinki District using samples from Suemura kilns (II)
Keywords:Archeomagnetism, Geomagnetic secular variation
The most of the measurements are carried out in Kumamoto University. One pilot sample is selected for progressive a.f. demagnetization. If the result is understood strait forward, the remaining samples are submitted to blanket demagnetization with the strength determined from zijderveldt diagram. Otherwise, all the samples are progressively demagnetized. Almost all the samples has very stable magnetization as usual as well baked kiln samples, the difference of magnetic direction of different demagnetization strength is minimal. One in a site is reserved undemagnetized for future paleointensity studies.
The problem reported at the previous meeting is the existence of outliers. They are statistically excluded to get the site mean, and draw tentative PSV curve. Besides the same technique, we made the density map of all the sample direction, and draw the PSV curve as the trace of the ridge of the density. This technique has also advantage that it can utilize the sites of unknown age. The PSV curve obtained is similar to the previous works, though the amplitude of inclination variation is slightly larger. The density map seems to show that there are a few gaps in the density map. It may reflect the gap of the pottery production in the area