Authors:
Gengen Qiu
;
Hui Fang
;
Jie Zhang
;
Fagen Pei
;
Qingyin Lv
and
Yan Peng
Affiliation:
Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences, Langfang and Hebei, China
Keyword(s):
Magnetotelluric, Changbai Mountain, magma chamber
Abstract:
To address the foreign media’s comments that the Tianchi Volcano in Changbai Mountain is likely to erupt in the near future, we collected a magnetotelluric (MT) observation profile approximately 120 km in length in the area to detect the deep electrical structures of magma chamber. Because electromagnetic noise from an unknown source is very strong in the research area, we used remote-referencing and robust processing, rhoplus analysis, impedance tensor decomposition, and a mutual approximate calculating method between apparent resistivity and phase for MT data processing . These techniques resulted in relatively reliable electromagnetic response data in the strong electromagnetic noise area. The results show that there is a clear magma channel beneath Tianchi Volcano, at a depth of approximately 10 km. An obvious abnormal body of low resistance, where resistivity is less than 10 Ω•m connects with the magma channel at 7 km deep and north of the existing crater, suggesting a developin
g magma chamber in the shallow surface. There are two nearly vertical low resistivity zones at 7-17 km in depth, one between stations C07-C09 and the other between stations C04-C05, that connect directly to the low resistance body directly; these low resistivity zones are likely active fault zones. Crustal low resistivity anomaly bodies are widely developed at depths of 13 – 30 km about 20 km south of Tianchi Volcano, suggesting an active magma chamber. The MT sounding method results indicate that Changbai Mountain has a high risk of volcanic eruption, and the MT method performed well detecting the state of current volcanism.
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