The ages of fault events of active faults have been estimated using electron spin resonance ESR signals of siliceous gouges. This technique of ESR method is limited by obtaining only ages that are greater than tens of millennia. So this study focuses on developing a new technique of using calcareous gouges to gain an insight into the ages of latest seismogenic event within the Holocene.
For the first time, signal B of the ESR method has been used to estimate the age of the Ushikubi fault from calcareous gouge. This technique proved reliable because the mean age 1.
Moreover, isochronal experiment revealed that the gouge did not comprise pure carbonates but consisted of a mixture of calcite and quartz grains.
A younger age value would have been obtained if a lower artificial irradiation dose rate and a relatively pure carbonate fault gouge were used in the ED determination. Active tectonics is associated with uplifts, earthquakes, volcanic eruptions, landslides and faulting, which have been reported having a direct impact on the environment and population [ 12 ]. One of the countries in the World that is most vulnerable to the aforementioned components of active tectonics is Japan [ 34 ].
The environmental and human impacts from the incidence of active tectonics can among others be exemplified by the March 11, earthquake and tsunami along the northeastern coast of Japan, and the Niigata Chuetsu-Oki earthquakes.
These underscore the importance of monitoring of active tectonics. In recognition of this importance, earth scientists have not only intensified but also refined on both spatial and temporal dimensions the characterization of faults and earthquake prone zones in Japan. As far as temporal characterization is concerned, quartz in fault gouges has been used to estimate the age of latest fault movements using the electron spin resonance ESR method [ 5 — 8 ].
The established ESR method reported by Ikeya et al. Among these defect centers, a paramagnetic center called oxygen vacancy with one electron center has been used extensively to characterize and date faults. However, ESR results gotten through this signal are unlikely because of the Electron spin resonance esr dating of quaternary materials engineer reasons: Irrespective of all attempts to date young faults with the ESR method using defect centers in quartz, the main limitation reported by Noller et al.
Because of the importance of understanding active faults and estimating the age of faults to improve upon the mitigation management and hazard assessment [ 11 ], various investigations by various methods have been employed to elucidate the recent history and activity of the Ushikubi fault in central Japan.
Some of these investigations include: Although the age of the latest event of the Ushikubi fault has been estimated indirectly using the radiocarbon dating method, the ESR method has not yet been employed. Accordingly, this study employs a novel of using calcareous gouge as an active fault dating material to supplement the existing methods with the main objective to identify a useful ESR signal for dating of calcareous fault gouge and also develop a method to determine the age of the latest seismogenic event of the Ushikubi Fault in central Japan.
This area shows a rugged relief, with incised valleys, which are drained by the Jinzu, Joganji and Shou rivers [ 13 ]. The northern margin of the Hida highlands belongs to the Hida geologic belt. The basement consists of Paleozoic Hida metamorphic rocks felsic gneiss, hornblende gneiss, meta-mafic rocks, crystalline limestone and calcareous gneiss that contain biotite.
These basements are intruded by Jurassic Funatsu granites which are overlain by Cretaceous sedimentary rocks of the Tetori group sandstones, mudstones, conglomerates [ 13 ] Fig.
Index map showing the location of the Ushikubi fault and sample locations in Japan modified from [ 30 ] EPU the eastern part of the Ushikubi fault, CPU the central part of the Ushikubi fault.
Geological map around the northern margin of the Hida highland edited from [ 2829 ]. The method of the study was conducted in two phases: The sites from where the various samples were collected are shown in Figs. The fresh landslide scar exposed weathered and crushed remains of the Tetori group, gravel layer and relics of the Hida metamorphic rocks. The Tetori group in this outcrop is represented by sandstones and mudstones which have been crushed to form breccias, cataclasites and fault gouges.
The fault gouge within this zone exhibits a hue of colors such as grayish black, bluish gray, greenish, pinkish and whitish. Fresh samples were carefully collected from the light-colored portion of the fault gouge with the intention of obtaining calcite-rich gouges. After sampling, the samples were then washed with distilled water and then allowed to dry in a dark room. With the aid of an electron microscope, it was observed that the sieved grains varied in shape such as tabular, angular, sub-angular to angular and sub-rounded to rounded.
The estimated proportion of the different grain Electron spin resonance esr dating of quaternary materials engineer was as shown in Fig. X-ray diffraction patterns also indicate the presence of calcite in the fault gouge Fig.
The obtained calcareous gouge was then analyzed in the laboratory with the ESR method. Photographs on the right represent the core samples that were used in this study. The red rectangles show areas where samples were taken at different depth BVB-5a at 27— Black lines across the core samples demarcate different formations. The samples of interest were taken from the uppermost layer of the different core samples.
The sketch corresponds to the area in the form of a trapezium with thick black lines.
This shear zone represents relics of the Tetori group and the Hida metamorphic rocks that were crushed to form the gouge color figure online. Relationship between grain size and grain shape in the calcareous fault gouge. Larger grains are mostly tabular to angular in shape and fine grains constitute the ground mass. Graph b shows angular grains dominating in both fractions.
The proportion of calcite Ca in this size fraction is greater than that of quartz Qtz. The proportion of quartz Qtz in this size fraction is greater than that of calcite Ca. Thin sections were prepared using microslide glass with thickness of 1. Prior to ESR analysis, the gouge samples were washed with distilled water and then dried in a dark environment to avoid possible effects of sunlight on the ESR signal intensity [ 10 ].
More over, calcite with a hardness of 2. Colored and sizable grains were also removed by hand picking with the aid of a microscope. The samples were then tested with dilute HCl to verify and confirm the presence of carbonate in the gouge. An ESR spectrometer operating at an X-band frequency was the typical spectrometer that was used in this study. The purpose for using these conditions was to enable comparison with other spectra of the same species.
Moreover, with those conditions, the reproducibility of the signal intensities for the different samples yielded better results after conducting a series of control experiments on signals of the same species.
A sweep width of 7. The intensity of each signal in each sample was then taken as the peak-to-peak height. The heated samples were then allowed to cool down in desiccators to avoid the absorption of moisture. The samples were then analyzed with the ESR spectrometer under the above-mentioned conditions at room temperature. The obtained results were then used for the determination of the Electron spin resonance esr dating of quaternary materials engineer dose ED Gy.
ESR ages were then calculated using the relationship. Thin sections used in this study were prepared using microslide glass with a thickness of 1.
Three distinct peaks signals were identified in both the surface and the core samples. It is worth noting that to recognize a signal base on its g value only is not sufficient to label a paramagnetic center [ 20 ]. Signals A, B and C are ascribed torespectively. Because of the difficulties in distinguishing and assigning g values to various paramagnetic defect centers in the samples, isochronal annealing experiments were performed on some of the samples CFG4, CFG2, CFG1 and BVB-5a.
From the isochronal curves,
Electron spin resonance esr dating of quaternary materials engineer decrease in signal intensity occurred in two stages as shown in Fig. This unique behavior in the decay pattern of signal C in the different samples is attributed to the presence of defect center in quartz whose intensity increases with increase in temperature.
The annealing experiment was done in an Isuzu muffle oven. The ESR intensity of signal C equally showed a unique behavior. A general decrease in the intensities of signals A and B was equally observed in this sample while that of signal C decreased in two stages as the temperature was increased.
The ESR spectra of the artificially irradiated samples East.
Neither pre- nor pro-thermal treatment was done on the artificially irradiated samples. At lower levels of artificial irradiation, the intensities of the different signals were enhanced and there was no growth with increasing irradiation dose implying signal saturation. A decrease in signal intensity was observed in some of the peaks e.
Although an increase in signal intensity was observed at a lower dose range, some signals got saturated as the dose was increased. The overall observation in the saturation behavior of some of the signals with increasing dose is summarized in Fig.
Summary of the saturation behavior of the ESR spectra e. When signal intensity does not increase upon addition of artificial irradiation dose, it means signal are saturated. The A, B and C signals are attributed to therespectively [ 1021 ]. The signal C corresponding to the is the most frequently used signals in carbonate dating [ 1021 ].
The slight variation in the temperatures could be as a result of an additional defect center center since the samples contained a mixture of quartz and calcite as shown in the micrograph of Fig. One possible explanation for the variation in the temperature could also be that the samples investigated are different from those previously investigated by other researchers carbonates in fossils, speleothem, fault gouge, etc. From the isochronal curves Fig.
These results are consistent with the observation of Toyoda and Schwarcz [ 7 ] and Ikeya et al. Moreover, at a low to moderate microwave power, its dependency showed a saturation behavior of this peak as shown in Fig. The defect center in quartz saturates easily at low microwave power as reported by Hataya Electron spin resonance esr dating of quaternary materials engineer al. This signal is not greatly upon artificial irradiation Fig.
The intensity of this signal increased with increasing temperature at the expense of signal B Fig. The microwave power dependence of this signal shows that this signal does not saturate even at a moderate to high microwave power Fig. This observation is supported by the findings of Ikeya et al. This signal is enhanced by artificial irradiation Fig. Signal C saturates at a moderate to high microwave power, while signals A and B do not saturate even at high microwave power.
The saturation pattern of the different signals are the same in the different samples investigated, e. However, the degree of saturation varies among different signals in different samples. To estimate the ESR-based age T ESR of the latest event of the Ushikubi fault using calcareous fault gouge, the equivalent dose ED and the annual dose rate D were key parameters used as stated in [ 10 ].
The equivalent dose Fig.
Engineering Group Working Party Report J.S. Griffiths, C.J.