A deep transient EM experiment in the northern part of Miyagi Prefecture, northeastern Japan
A deep transient EM experiment in the northern part of Miyagi Prefecture, northeastern Japan
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日本东北部宫城县北部的深层瞬态电磁实验
DOI：
10.5636/jgg.48.1265
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
N. Sumitomo
中科院分区：
文献类型：
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作者：
W. Kanda;H. Utada;M. Mishina;N. Sumitomo
1993年11月，在日本东北部宫城县的北方进行了一次时域电磁（TDEM）实验。观测区为高地震活动区，1962年曾发生6.5级地震，至今仍能观测到其余震。这次观测的目的是研究这种地震活动与电阻率结构的关系。我们的目标是调查最近发生地震的10公里左右深度的电阻率结构。对于现场实验，使用约2km长的接地线作为人工源。接收器位于距离发射器几公里的地方，使用高灵敏度磁通门磁力计测量磁场的三个分量。高质量的瞬态数据是从10个站点的4天的测量中获得的，总数据长度约为27小时。在应用适当的数据分析技术后，通过将垂直磁分量和水平磁分量与一维电阻率模型的合成主曲线进行比较来估计电阻率结构。初步结果表明，测区东北部以下存在一个高导地壳层，微震活动较浅。另一方面，在地震活动较深的西南部，在野外穿透深度范围内，我们找不到地壳导体。
In November 1993, a time domain electro-magnetic (TDEM) experiment was carried out in the northern part of Miyagi Prefecture, northeastern Japan. The observation area is of high seismic activity, where a magnitude 6.5 earthquake occurred in 1962 and its aftershocks can be still observed. The purpose of this observation is to investigate how this seismic activity is related to the electric resistivity structure. We aimed to investigate the resistivity structure down to a depth of 10 km or so, where most recent earthquakes took place. For the field experiment, an approximately 2 km long grounded wire was used as an artificial source. Receivers were located at a distance of several kilometers from the transmitter, where three components of the magnetic field were measured using a high sensitivity fluxgate magnetometer. High quality transient data were obtained from measurements made at 10 sites for 4 days, with total data length of about 27 hours. After proper techniques of the data analysis were applied, the resistivity structure was estimated by comparing not only the vertical but also the horizontal magnetic components with the synthetic master curve for one dimensional (1-D) resistivity model. Preliminary result shows that a highly conducting crustal layer exists below the north-eastern part of the survey area where micro seismicity is rather shallower. On the other hand, we could not find a crustal conductor within the range of field penetration depth in the southwestern part, where seismicity is deeper.