Asama Volcano, Central Japan

• Location of Asama Volcano
• Aeromagnetic Anomaly Map of Asama Volcano
• Relationship between Aeromagnetic Anomalies and Geology
• Characteristics of Magnetic Anomalies

Location of Asama Volcano

Fig.1 Location map of Asama volcano

Fig.2 Picture of Asama volcano (Okuma et al., 1997)
Taken from Karuizawa Town, Nagano Prefecture, south of the volcano in 1992.　

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Aeromagnetic Anomaly Map of Asama Volcano

Fig.3 Total intensity magnetic anomaly map of Asama volcano with a topographic shading (Makino et al., 1993; Okuma et al., 1997)
Contour interval is 50 (nT).

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Relationship between Aeromagnetic Anomalies and Geology

Fig.4 Total intensity magnetic anomalies of Asama volcano superimposed on a geologic map (modified from Okuma et al. (1997))
Contour interval is 50 (nT). H and L denote a magnetic high and low, respectively. Geological map of Asama volcano (Aramaki, 1993) was employed. The map area corresponds to that of Fig. 3.

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Characteristics of Magnetic Anomalies

(1) Obvious magnetic highs lie over the southern side of each topographic highs: Kurofu-yama, Kenga-mine, Maekake-yama, Hotoke-iwa and Sekison-zan.

(2) The area of high magnetic anomalies on the southeast flank of Asama volcano suggests the subsurface extent of the Hotoke-iwa Lava Flows.

(3) Weak magnetic highs lie over the Onioshidashi Lava, the Maekake-yama Lava on the northern flank of the volcano and the southern flank of the Koasama-yama.

(4) An obvious magnetic low occupies the Yunotaira Area,where is believed to be the center of the oldest member of Asama volcano, Kurofu-yama, suggesting hydrothermal alterations.

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