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Journal Articles

A Fault dating method using an electron spin resonance

Tanaka, Kiriha*; Muto, Jun*; Nagahama, Hiroyuki*; Oka, Toshitaka

Hoshasen Kagaku (Internet), (110), p.21 - 30, 2020/10

In a fault dating by electron spin resonance (ESR), the number of unpaired electrons trapped in defects in minerals contained in a fault material is detected as ESR intensity. Based on the quantitative change of the intensity before and after an earthquake, the last age of a fault movement can be estimated. However, this method has a hypothesis called "zero-setting" which assumes the decrease in the ESR intensity to zero by fault movement during an earthquake. In order to understand and demonstrate zero-setting, the analysis of the natural fault materials and experiments mimicking fault movements have been conducted. In this paper, we summarized the previous studies about zero-setting by fault movement and described the current status and challenges.

Journal Articles

Measurement of angular dependent neutron production from thick target bombarded with 140-MeV protons

Iwamoto, Yosuke; Satoh, Daiki; Hagiwara, Masayuki*; Iwase, Hiroshi*; Kirihara, Yoichi*; Yashima, Hiroshi*; Nakane, Yoshihiro; Nakashima, Hiroshi; Nakamura, Takashi*; Tamii, Atsushi*; et al.

Nuclear Technology, 168(2), p.340 - 344, 2009/11

 Times Cited Count:4 Percentile:32.89(Nuclear Science & Technology)

It is important to calculate neutron production from thick targets at forward angle near 0 degree and backward angle near 180 degree for the shielding design of proton accelerator facilities, and the accuracy should be determined by experimental data. There are, however, few experimental data near 0 degree, and no data near 180 degree in the energy region above 100 MeV. Neutron energy spectra at 0, 90 and 180 degrees produced from thick graphite and iron targets by 140 MeV protons were measured. It was found that the calculation with JENDL-HE was more suitable for the shielding design of proton accelerator facilities in the forward direction.

Journal Articles

Measurement of thick target neutron yields at 0$$^{circ}$$ bombarded with 140, 250 and 350 MeV protons

Iwamoto, Yosuke; Taniguchi, Shingo*; Nakao, Noriaki*; Itoga, Toshio*; Yashima, Hiroshi*; Nakamura, Takashi*; Satoh, Daiki; Nakane, Yoshihiro; Nakashima, Hiroshi; Kirihara, Yoichi*; et al.

Nuclear Instruments and Methods in Physics Research A, 593(3), p.298 - 306, 2008/08

 Times Cited Count:10 Percentile:59.39(Instruments & Instrumentation)

Neutron energy spectra at 0$$^{circ}$$ produced from stopping-length graphite, aluminum, iron and lead targets bombarded with 140, 250 and 350 MeV protons were measured at the neutron TOF course in RCNP of Osaka University. The neutron energy spectra were obtained by using the time-of-flight technique in the energy range from 10 MeV to incident proton energy. To compare the experimental results, Monte Carlo calculations with the PHITS and MCNPX codes were performed using the JENDL-HE and the LA150 evaluated nuclear data files, the ISOBAR model implemented in PHITS, and the LAHET code in MCNPX. It was found that these calculated results at 0$$^{circ}$$ generally agreed with the experimental results in the energy range above 20 MeV except for graphite at 250 and 350 MeV.

Oral presentation

Supporting the surface charging mechanism of seismic-electromagnetic phenomena by the direct measurements of the electron and hole trapping centers

Tanaka, Kiriha*; Nagahama, Hiroyuki*; Muto, Jun*; Oka, Toshitaka; Yabe, Yasuo*

no journal, , 

The mechanisms of the seismic-electromagnetic phenomena attracted as precursors of short-term earthquake forecast have been suggested, however, it is still incompletely understood. Our results showed that the fracture by fault motions could produce the surface charges on the fault. It proves that the electromagnetic abnormalities by the fault motions may also be observed through the surface charging mechanism. Therefore, our study supports that the surface charging mechanism is plausible.

Oral presentation

Effect of seismic fault slips at various depths on the E$$_{1}^{'}$$ center in Quartz

Tanaka, Kiriha*; Muto, Jun*; Takahashi, Miki*; Jayawickrama, E.*; Sasaki, Osamu*; Oka, Toshitaka; Nagahama, Hiroyuki*

no journal, , 

A fault dating using electron spin resonance (ESR) is a developing direct method to estimate the age of the last fault movement. This method hypothesizes that natural radiation-induced ESR intensity, which is proportional to the concentration of charges trapped in defects accumulated in the interseismic period, is completely reset due to fracture, stress, and frictional heating by a seismic fault slip. The incomplete zeroing can result in age overestimation, hence, the understanding of its detailed conditions and mechanism is required. We have performed high-velocity friction experiments under various normal stresses to investigate the possibility for the signal zeroing by seismic fault slips at various depths. We infer that the degrees of grain fracture and frictional heating associated with the seismic fault slip originating from fault heterogeneity yield the complicated zeroing mechanism of the E$$_{1}^{'}$$ center.

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