3차원 MT 탐사 자료의 바다효과 보정
Sea-effect Correction of 3D Magnetotelluric Responses
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초록
In order to investigate geothermal energey resources, Korea Institute of Geoscience and Mineral Resources (KIGAM) have coducted magnetotellurics (MT) surveys for years in Pohang and Jeju, Korea. Since the survey sites are close to sea, low-frequency MT data measured in Pohang and Jeju are not free from sea effects. Subsequently, inversion of MT data may result in misinterpretation of the subsurface if sea effects are not considered properly. The sea effects can be considered in the interpretation of MT data in two different ways: incorporating sea into an earth model in inversion and compensating sea effects from MT data before conducting inversion. The first approach may suffer from numerical difficulties due to the presence of electrically conductive sea. Using the second method, we can invert distorted MT data using currently available inversion algorithms that were designed for a model without sea. This paper presents a method to compensate sea effects on MT data by correcting both electric and magnetic fields distorted by sea effects. We validate the correction scheme using synthetic models with one or two-layered hosts. Nonlinear least-squares inversion of corrected MT data successfully recovers major features of the synthetic model.
Abstract
In order to investigate geothermal energey resources, Korea Institute of Geoscience and Mineral Resources (KIGAM) have coducted magnetotellurics (MT) surveys for years in Pohang and Jeju, Korea. Since the survey sites are close to sea, low-frequency MT data measured in Pohang and Jeju are not free from sea effects. Subsequently, inversion of MT data may result in misinterpretation of the subsurface if sea effects are not considered properly. The sea effects can be considered in the interpretation of MT data in two different ways: incorporating sea into an earth model in inversion and compensating sea effects from MT data before conducting inversion. The first approach may suffer from numerical difficulties due to the presence of electrically conductive sea. Using the second method, we can invert distorted MT data using currently available inversion algorithms that were designed for a model without sea. This paper presents a method to compensate sea effects on MT data by correcting both electric and magnetic fields distorted by sea effects. We validate the correction scheme using synthetic models with one or two-layered hosts. Nonlinear least-squares inversion of corrected MT data successfully recovers major features of the synthetic model.
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