17:15 〜 18:45
[SEM12-P11] Evaluation of the effect of lake level and temperature on CSEM transfer functions at Inferno Crater Lake, New Zealand
キーワード：EM-ACROSS法、比抵抗、インフェルノ火口湖、順問題
Inferno Crater Lake is situated in the Waimangu geothermal zone on New Zealand's North Island. The lake exhibits cyclical changes in water level and temperature, which can be explained by a proposed model where the two-phase region beneath the lake fluctuates. The resistivity of a rock is a physical quantity that provides information on the presence and condition of fluids. A previous electric survey identified a high resistivity region beneath the lake when the water level was high, which is consistent with the proposed model. However, the discussion did not address the effect of level fluctuation, and the 3-dimensional resistivity structure and its temporal changes remain unknown. Therefore, it is important to develop a resistivity monitoring method.
The EM-ACROSS (ElectroMagnetic-Accurately Controlled, Routinely Operated, Signal System) is a controlled-source electromagnetic transmission system. In 2023, an EM-ACROSS observation was conducted around the lake, and transfer functions were obtained. The phase tensor, which is calculated from the transfer function, correlates with the water level. To evaluate the effect of water level variability, a 3D forward modeling code was created that describes the topography and water level changes. The computational domain is filled with deformed and non-conforming hexahedral meshes. This code uses the vector finite element method to calculate the total electric fields on the edges of the meshes. This presentation will examine the effects of alterations in water levels and temperature on the transfer functions.
The EM-ACROSS (ElectroMagnetic-Accurately Controlled, Routinely Operated, Signal System) is a controlled-source electromagnetic transmission system. In 2023, an EM-ACROSS observation was conducted around the lake, and transfer functions were obtained. The phase tensor, which is calculated from the transfer function, correlates with the water level. To evaluate the effect of water level variability, a 3D forward modeling code was created that describes the topography and water level changes. The computational domain is filled with deformed and non-conforming hexahedral meshes. This code uses the vector finite element method to calculate the total electric fields on the edges of the meshes. This presentation will examine the effects of alterations in water levels and temperature on the transfer functions.