Application 3D magnetotelluric investigation for geothermal exploration

Toshihiro Uchida,Yoonho Song,Yuji Mitsuhata,Seong Kon Lee 한국암반공학회 2003 한국암반공학회 학술대회 및 세미나 자료집 Vol.- No.-

Three-dimensional magnetotelluric surveys for geothermal development in Pohang, Korea

Toshihiro Uchida,Tae Jong Lee,Yoonho Song 한국지구물리탐사학회 2007 지구물리와 물리탐사 Vol.10 No.1

Tunable magnetoresistance in thin-film graphite field-effect transistor by gate voltage

Taen, Toshihiro,Uchida, Kazuhito,Osada, Toshihito,Kang, Woun American Physical Society 2018 Physical Review B Vol.98 No.15

Magnetotelluric measurements along a reflection seismic profile: reprocessing and reinterpretation of MT data for crustal-scale electric resistivity structure in central Victoria, Australia

이성곤,이태종,Toshihiro Uchida,박인화,Tim Rawling,Jim Cull,송윤호 한국지질과학협의회 2013 Geosciences Journal Vol.17 No.3

Magnetotelluric(MT) soundings were done in Central Victoria, Australia, to investigate the electrical conductivity structure of the Bendigo and Melbourne structural zones. We reprocess and reinterpret the MT data, which were acquired along the same path as the seismic transect in 2006 by GeoScience Victoria (GSV). Deep crustal faulting in this region is considered to be responsible for significant mineralization and magmatic processes. The resulting two dimensional (2D) MT conductivity model is consistent with the seismic interpretation in that it clearly shows known boundaries as well, as additionally reveals four clearly isolated resistors, which could be hardly imaged by reflection seismic. With the result previously published, these resistors can be interpreted as granite or granodiorite intruded in the Devonian, or alteration associated with fluid migration. The 2-D electric conductivity model also agrees with seismic interpretations, which shows that internal faults in the Bendigo Zone are thrust fault systems with listric geometries that are connected in the mid-crust, and clarifies that the Bendigo Zone and Melbourne Zone experienced different tectonic evolution during the Benambran Orogeny in the Silurian. The model also supports the conjecture that the Melbourne Zone formed as a foreland basin to the uplifted Bendigo Zone.

가청주파수 대역 MT 탐사자료에서 원거리 기준점의 효과

송윤호,이태종,Toshihiro Uchida 한국자원공학회 2006 한국자원공학회지 Vol.43 No.1

Magnetotelluric (MT) survey in a high resistivity terrain throughout the conventional MT frequency range provides limited information on shallow subsurface and thus degenerates depth resolution on deep structures. Therefore, data acquisition for audio-frequency range (AMT) becomes important, but works on remote reference (RR) techniques on AMT have not been made. We performed RR data processing using the data obtained in Jeju Island with RR's apart 1 km, 26 km and 480 km and compared the results to figure out the effect of RR processing on AMT data. Comparison and analyses were conducted with time series samples, coherency, apparent resistivity and phase responses. As a result, we could get impedance responses for MT band being free from noises only with RR processing when 480 km apart, while RR at 26 km apart provided reasonable estimate of impedance for AMT band. Therefore, considering logistics of field survey, it is highly recommended to use two differently located RR's in processing and to merge the results to make final sounding responses. 우리나라와 같이 전기비저항이 높은 지역에서는 통상적인 MT 탐사의 주파수 대역만으로는 천부 지하구조에 대한 정확한 파악이 어려우며 따라서 심부에 대한 해상도도 떨어지게 된다. 따라서 가청주파수 대역에서의 MT (AMT) 탐사자료 획득이 매우 중요한데, 지금까지 이 대역에서의 원거리 기준점 운영은 이루어지지 않았다. AMT 자료처리에서 원거리 기준점의 효과를 알아보기 위해서, 제주도에서 획득한 MT 및 AMT 자료에 1 km, 26 km 및 480 km 떨어진 원거리 기준점 자료를 이용한 자료처리를 수행하여 그 결과를 비교하였다. 비교 분석은 시계열 자료, coherency 및 임피던스(겉보기 비저항과 위상차) 자료를 이용하였다. 그 결과로 MT 대역에서는 480 km 떨어진 원거리 기준점 자료를 사용하여야 잡음으로부터 자유로운 반응 곡선을 얻을 수 있음을 보여주었으며, AMT 대역에서는 26 km 떨어진 자료도 원거리 기준점으로 사용할 수 있음을 확인하였다. 따라서 현장 탐사의 신속성과 간편성을 동시에 고려하여, AMT 대역에서는 가까운 원거리 기준점을 이용하고 MT 대역에서는 매우 먼 거리의 원거리 기준점을 이용하여 각각 자료처리한 후, 두 결과를 조합함으로써 최적의 효율을 낼 수 있음을 보였다.

Application of electromagnetic methods to the investigation of seawater intrusion into coastal aquifer

Yuji Mitsuhata,Toshihiro Uchida 한국암반공학회 2003 한국암반공학회 학술대회 및 세미나 자료집 Vol.- No.-

포항 지열개발 지역 MT 탐사 자료의 2차원 및 3차원 해석

이태종,송윤호,Toshihiro Uchida 한국자원공학회 2005 한국자원공학회지 Vol.42 No.4

We have conducted three-dimensional magnetotelluric (MT) measurements in the Pohang geothermal site. Then, we have applied the two- (2-D) and three-dimensional (3-D) inversion to delineate the deep geological structures including possible fractures. The 3-D inversion algorithm adopted in this study is a linearized least-squares inversion scheme with static shift parameterization as well as with smoothness regularization. The scheme showed stable convergence at each iterations and eventually provided smooth 3-D resistivity model of the site. The resultant 2-D and 3-D resistivity model revealed overall consistency with each other as well as with core and geophysical logging. In 2-D interpretation, however, care must be taken to the artifacts, which can be created by a 3-D structure beneath or off the survey line. General geological feature of the survey can be summarized as follows. A thick conductive overburden of Tertiary sediments having about 10 ohm-m resistivity is as thick as more than 500 m in southern parts and 200 m in the north most part of the survey area. The 2-D and 3-D results commonly showed the conductive anomalies running NNE-SSW and NW-SE, respectively, and which can be considered as fracture systems. There could also be seen a conductive layer of about 10 ohm-m at 3 ~ 4 km depth of west and south parts of the survey area. 경상북도 포항시 흥해읍 일대에서 지열자원개발을 위한 심부 파쇄대 탐지를 목적으로 3차원 MT 탐사자료를 획득하고, 이를 이용한 2차원 및 3차원 역산 결과를 비교, 검토하였다. 정적효과를 역산변수로 포함하는 3차원 역산 알고리듬으로 지표에서 측정된 두 방향 성분의 겉보기 비저항과 위상자료를 이용하여 매우 안정적인 역산이 이루어 졌으며, 결과로서 얻어진 3차원 전기비저항 모델은 지질주상도 및 전기검층에서 나타나는 대표적인 각 지층들의 전기비저항 및 심도를 매우 잘 표현하여 3차원 역산 해석의 가능성을 보였다. 이 3차원 모델과 TM 모드 역산에 의한 2차원 모델은 대체적으로 매우 유사한 경향을 보였으나 복잡한 지질구조의 경우, 2차원 역산은 측선 주변 혹은 측선의 연장선 상에 존재하는 불균질체에 의한 영향이 역산단면상에 투영되어 나타나게 되므로 해석상에 주의를 요한다. 해석결과, 대상지역은 10 ohm-m 이내의 제 3기 반고결 이암층이 대상지역의 남쪽에서는 500 m 이상, 북쪽에서는 200 m 이내의 두께로 분포한다. 북북동-남남서 방향 및 북서-남동 방향의 전기비저항 이상대는 파쇄대로 해석되며, 대상지역의 서쪽과 남쪽의 3 ~ 4 km 하부에서 10 ohm-m 내외의 저비저항층이 존재하는 것으로 나타났으나 이 층에 대해서는 향후 추가적인 연구가 필요하다.

Predictive factors and radiological findings of adrenohepatic adhesion during laparoscopic adrenalectomy

Katsuhiro Ito,Hiromasa Araki,Toshihiro Uchida,Yumi Manabe,Yu Miyazaki,Haruki Itoh,Mutsuki Mishina,Hiroshi Okuno 대한비뇨의학회 2020 Investigative and Clinical Urology Vol.61 No.3

Purpose: This retrospective study aimed to identify predictive factors and imaging features of adrenohepatic adhesion found during laparoscopic right adrenalectomy. Materials and Methods: Altogether, 77 patients underwent laparoscopic right adrenalectomy between January 2005 and December 2018. Adrenohepatic adhesion was defined as strict adhesion that required either partial adrenalectomy with coagulation of residual tissue or partial hepatectomy to accomplish complete resection. We assessed their surgical video records to determine if adrenohepatic adhesion was present. Age, sex, body mass index, tumor size, tumor diagnosis and radiological findings (attachment between the liver and the adrenal gland, diameters of the right and left adrenal veins and its ratio) were evaluated as preoperative variables. Results: Adrenohepatic adhesion was present in 11 of the 77 patients (14.3%). Age, sex, and body mass index were not statistically significant factors. Tumor size was significantly small in adhesion group (14.2 mm vs. 25.9 mm, p=0.02). Attachment to the liver and adrenal gland was frequently seen regardless of the adhesion. The mean right/left adrenal veins diameters ratio was significantly lower in the adhesion group (0.8 vs. 1.1, p=0.01). Multivariate logistic regression analysis demonstrated the right/left adrenal veins diameters ratio was the only significant predictor of adhesion. The sensitivity, specificity, negative predictive value and positive predictive value were 0.82, 0.76, 0.43, and 0.95 respectively when the optimal cutoff value for the ratio was 0.9 (area under the curve, 0.75; 95% confidence interval, 0.60–0.90). Conclusions: The right/left adrenal veins diameters ratio was possible predictor of adrenohepatic adhesion.

심부 지열자원 부존 가능성 탐지를 위한 제주 중산간 지역의 2차원 MT 탐사

이태종,이성곤,이춘기,박인화,송윤호,Toshihiro Uchida 한국자원공학회 2008 한국자원공학회지 Vol.45 No.4

Two-dimensional magnetotelluric (MT) and audio-frequency MT (AMT) surveys have been carried out at the mid-mountain area of Jeju Island to figure out any possible structures or evidences for remnant deep geothermal energy. Though numerous drillings have been performed in Jeju Island for development of ground water, the wells are mostly located along the coast lines or at low altitude area, but can hardly be found on the mid-mountain area. Good quality of MT and AMT data could be earned by operating far-remote reference in Kyushu Island, Japan, which is approximately 480 km apart. Two-dimensional inversion of MT data for four survey lines surrounding the Halla mountain showed a thick layer having around 10 ohm-m in the depth of a few hundred meters throughout the survey area, which can be considered as the unconsolidated sedimentary layer and the marine originated sedimentary layer. They also showed a conductive anomaly extending to more than 2 km depth at the central part of each survey line, which can possibly be a hydrothermal system or clays related with old volcanic activities during the formation of Mt. Halla.

논문 : 지구과학 교육과정의 새로운 방향 모색 ; 지진파에 의해 유도되는 전자기장 변동

이춘기,이희순,권병두,양준모,오석훈,송윤호,이태종,( Toshihiro Uchida ) 한국지구과학회 2005 지구과학 교육심포지엄 및 춘계학술발표회 Vol.2005 No.-