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Muography in Showa- Shinzan Lava Dome

Muography in Showa- Shinzan Lava Dome. R. Nishiyama Earthquake Research Institute, University of Tokyo 26 July 2013, MNR workshop 2013, Tokyo. Contents. Eruption History of Showa- Shinzan Geophysical Surveys (a). Precedent studies (b). Muography in 2007

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Muography in Showa- Shinzan Lava Dome

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  1. Muography in Showa-Shinzan Lava Dome R. Nishiyama Earthquake Research Institute, University of Tokyo 26 July 2013, MNR workshop 2013, Tokyo

  2. Contents • Eruption History of Showa-Shinzan • Geophysical Surveys • (a). Precedent studies • (b). Muographyin 2007 • (c). Joint analysis of muography and gravity measurements • Implication • What we can say now • What we want to see …

  3. Showa-Shinzan Lava Dome • Eruption history (Dec. 1943 ~ Sep. 1945, Usu) • (0). wheat field • (1). volcanic earthquakes and significant ground uplift • (2). paroxysmal explosions at craters on the uplifted plateau • (3). dacite magma extruded from below the plateau Minakami et al. [1951] roof-mountain (uplifted-plateau) dacite lava dome dacite lava dome roof-mountain (1). pre-volcanic stage (2). paroxysmal eruption size & shape of conduit ? density (porosity) variation ? (3). development of dome Morphological development recorded by Mimatasu[1962].

  4. Precedent geophysical surveys • seismic survey(Nemoto et al., 1957) • Reflection of seismic wave at magma-soil boundary. geomagnetic survey (Nishida and Miyajima., JVGR, 1984) “The root of the lave dome of Mt. Showa-Shinzan has almost the same diameter as that of the dome exposed on the earth's surface.” gravity survey (Nemoto et al., 1957) 1 mgal positive Bouguer anomaly on the top of the dome. Shape of lava plugs have been studied by various studies.

  5. Muography in 2007 Average density profile Tanaka et al., GRL, 2007

  6. Joint analysis: muography + gravity → 3D You can see details in my afternoon talk. muography data Gravity data Nishiyama et al. submitting.

  7. Implications • Uplifted plateau (east, low density) • Dome region (west, high density) • Two significant high density anomalies • H1: solidified lava stuck in a vent • H2: H2

  8. future applications • ■ 3D density map → 3D porosity map • Non-invasive measurement of porosity inside the vent.(c.f. Stasiuk et al., BV 1996) measured from composition

  9. Thank you.

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