| 講演要旨(和文) | | MTインピーダンスは電流源の空間的・時間的特性に影響を受けることが知られている．しかしながら，インピーダンスの時間的変動が単純に電流源によって説明が出来ない場合もある．そこで、地磁気変動の空間・強度特性を考慮しつつ，その変動の原因について究明した．柿岡地磁気観測所のMTデータから，インピーダンスの回転不変量の時間的変動を導出した．その結果，地上磁場変動の空間・強度特性とは独立に，インピーダンスの時間的変動が発生することが明らかとなった．原因の1つとして，降雨量の明確な違いが時間的変動の前後で存在した．我々は完全に電流源の状態を把握できるわけではないが，発生したMTインピーダンスの時間的変動は地下の環境を反映している可能性がある． |
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| | 講演要旨(英文) | | Magnetotelluric (MT) response functions are well known to be affected by the spatial or strength property of source field. However, there are several cases that the temporal changes of MT responses over the estimated errors cannot be explained simply by the source field. Therefore, we evaluated the cause of such cases taking the spatial and strength property of geomagnetic variations into consideration. We derived SSQ impedance (rotational invariants) from the MT data acquired at Kakioka Magnetic Observatory, Japan. Moreover, we derived the spatial and strength property of geomagnetic variations in order to evaluate the effect of source field on the SSQ impedance. As a result, the SSQ impedance changed temporally over their estimated errors even under the condition that the spatial and strength property of geomagnetic variations did not vary. Also, there are clear difference of precipitation amount between before and after such SSQ impedance's changes. The SSQ impedance's changes may possibly reflect the subsurface environment although we cannot know the condition of source field perfectly. |
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