The insensitivity of the cosmic ray galactic anisotropy to heliomagnetic polarity reversals

Using the cosmic ray sidereal and anti-sidereal diurnal variations observed underground in London and Hobart during the period 1958–1983, it is demonstrated that: (1) the phase changes of the apparent sidereal diurnal variation observed only in the Northern Hemisphere cannot be attributed to the change of the heliomagnetospheric modulation of galactic cosmic ray anisotropy caused by the polarity reversal of the solar magnetic field, but that they are due to the fluctuation of the spurious sidereal variation produced from the anisotropy responsible for the solar semi-diurnal variation; (2) the spurious sidereal variation can be eliminated from the apparent variation by using the observed anti-sidereal diurnal variation; and (3) after the elimination, the sidereal diurnal variations in the Northern and Southern Hemispheres almost coincide with each other and are stationary throughout the period, regardless of the polarity reversal of the heliomagnetosphere. The origin of the corrected sidereal variation is discussed.     

Piemontite from the manganiferous hematite ore deposits in the Tokoro Belt,Hokkaido, Japan

Summary Piemontites occur in manganiferous hematite ore deposits and radiolarian chest in the Nikoro Group, Tokoro Belt, eastern Hokkaido, Japan. The piemontite-bearing chest and ore bodies have suffered low-grade metamorphism of high pressure intermediate type. In ore bodies, piemontite forms veinlets with quartz and/or pumpellyite-(Mn²⁺) containing Mn³⁺ in Y site. In chest, piemontite occurs not only in veinlets but also in radiolarian tests with pumpellyite-(Mn²⁺). The mineral assemblages characterized by piemontite, pumpellyite-(Mn²⁺), okhotskite, hematite and bixbyite indicate that chest and ore deposits were metamorphosed under extremely highfO₂ condition. Some piemontites in ores contain as much as 1.12 Mn³⁺, and the sum of Mn³⁺ and Fe³⁺ attains 1.46 per formula unit, whereas piemontites in chest contain less (Mn³⁺ + Fe³⁺). This difference in compositions may essentially be ascribed to the difference in the host rock compositions. On the other hand, Mn³⁺ and Fe³⁺ contents of piemontites in ores vary considerably by Al (Mn³⁺, Fe³⁺) and Mn³⁺ Fe³⁺ substitutions. This phenomenon may be interpreted in terms of the local availability of Mn³⁺ and Fe³⁺ in the host rocks.The low-temperature stability limit of piemontite is evaluated from the relations between piemontite and pumpellyite and from the estimated P-T conditions of piemontite crystallization in chert and ore deposits.

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Piemontit aus den manganreichen Hematit-Lagerstätten des Tokoro-Gürtels, Hokkaido, Japan

Zusammenfassung Piemontite treten in manganführenden Hämatitlagerstätten und Radiolariten in der Nikoro-Gruppe des Tokoro-Gürtels, Ost-Hokkaido, Japan; auf. Die Piemontit-füh-renden Radiolarite und Erzkörper zeigen eine niedrig temperierte (Low-grade Bereich), Hochdruck (intermediate-type)-Metamorphose. In den Erzkörpern bildet Piemontit Gänge zusammen mit Quarz und/oder Mn³⁺ (in der Y-Position)-führendem Pumpellyit-(Mn²⁺). In den Radiolariten tritt Piemontit nicht nur in Gängen, sondern auch zusammen mit Pumpellyit-(Mn²⁺) in Radiolarien auf. Die Mineralparagenese Piemontit, Pumpellyit-(Mn²⁺), Okhotskit, Hämatit und Bixbyit deutet darauf hin, daß die Radiolarite und Erzlagerstätten unter hohenfO₂-Bedingungen metamorphisiert worden sind.In den Erzkörpern enthalten einige Piemontite bis zu 1.12 Mn³⁺ und die Summe von Mn³⁺ und Fe³⁺ erreicht 1.46 pro Formeleinheit. Die Piemontite in den Radiolariten zeigen geringere Mn³⁺ + Fe³⁺ Gehalte. Diese Unterschiede in der Zusammensetzung sind auf die unterschiedlichen Trägergesteine zurückzuführen. Außerdem variieren die Mn³⁺ und Fe³⁺-Gehalte der Piemontite in den Erzkörpern deutlich auf Grund der Substitution von Al (Mn³⁺, Fe³⁺) und Mn³⁺ Fe³⁺. Dieses Phänomen kann durch die lokale Verfügbarkeit von Mn³⁺ und Fe³⁺ im Trägergestein interpretiert werden.Die niedrige Temperatur-Stabilität von Piemontit kann durch die Assoziation Piemontit-Pumpellyit und durch die bestimmten P-T-Bedingungen der Piemontit-Kristallisation in den Radiolariten und Erzlagerstätten abgeschätzt werden.

     

ESR dating of quaternary tephra from Mt. Osore-zan using Al and Ti centres in quartz

Quaternary tephra of Mt. Osore-zan was dated by electron spin resonance. Quartz grains were separated from the tephra and ESR signals of Al and Ti centres were measured at 77 K. The signals of Al and Ti centres which have a complicated hyperfine structure were simplified by using wider field modulations width (5 gauss) than usually used (0.5–1 gauss). The influence of 5 gauss modulation width on the measurement of the signal intensity of Al and Ti centres was investigated. The intensity of the signal increases linearly with gamma irradiation and total doses obtained were 178 to 273 Gy and ESR ages were 0.19 to 0.32 Ma. These ages agree with the estimated age of about 0.3 Ma from the correlation of volcanic ash and terrace level.     

Isotopic compositions of potassium and calcium in magnetic spherules from marine sediments

Isotopic compositions of potassium and calcium in individual magnetic spherules were determined. No significant anomaly was observed for potassium within twice the statistical error (2σ), although for calcium isotopes enrichments of⁴⁶Ca,⁴⁴Ca and⁴²Ca were observed in one spherule. The relative excess of⁴⁶Ca,⁴⁴Ca and⁴²Ca in the spherule agrees with the relative yield of spallogenic calcium isotopes observed in iron meteorites. This fact indicates that the enrichment in the calcium isotopes was caused by cosmic ray irradiation of the spherule in outer space.     

Primary migration theory of petroleum and its application to petroleum exploration

Current concepts of oil and gas generation by thermal decomposition of kerogen are reviewed. Primary oil migration mechanisms requiring large quantities of water to serve as a carrier for the movement of oil from source rock to reservoir are discussed. Previous investigators regarded the expulsion of interlayer water from montmorillonite and montmorillonite-illite mixed-layer minerals by transformation during diagenesis as the most important source of the carrier water.The process of diagenesis is subdivided into three stages based on the results of experimental compaction studies on montmorillonite clay, on studies of the expulsion mechanism of interlayer and interstitial waters, and on the observed changes in pores and mineral grains in argillaceous sediments during these stages. As a result, we concluded that the migration of oil chiefly occurs during the late compaction stage when the sediment's porosity ranges from 30 to 10%.This conclusion implies that a large amount of oil can move during the period when the active generation of oil corresponds with the primary migration of carrier water. For instance, in the oil-bearing Miocene sediments of the Akita area of northern Japan, the oil generation temperature ranged from 100 to 150°C and the average migration depth was between 1300 and 2600 m. Therefore, the possibility of large oil pool formation will be high in the basin where the paleo-geothermal gradient is about 5.0°C/100 m. In fact, it is expected that the paleo-geothermal gradients in the vicinities of large oil fields will be very close to this value.Prediction of the type and amount of hydrocarbons in the exploration area will be possible by an examination of the paleo-geothermal gradient in the area and by a study of the relation between absolute porosity and burial depth of argillaceous rocks.     

Statistical discrimination of foreshocks from other earthquake clusters

When earthquake activity begins, it may be a foreshock sequence to a larger earthquake, a swarm, or a simple main-shock-aftershock sequence. This paper is concerned with the conditional probability that it will be foreshock activity of a later larger earthquake, depending on the occurrence pattern of some early events in the sequence. The earthquake catalogue of the Japan Meteorological Agency (1926-1993, M_J≥4) is decomposed into a large number of clusters in time and space in order to compare statistical features of foreshocks with those of swarms and aftershocks. Using such a data set, Ogata, Utsu & Katsura (1995) revealed some discriminating features of foreshocks relative to the other types of clusters, for example the events' closer proximity in time and space, and a tendency towards chronologically increasing magnitudes, which encouraged us to construct models which forecast the probability of the earthquakes being foreshocks. Specifically, the probability is a function of the history of magnitude differences, spans between origin times and distances between epicentres within a cluster. For purposes of illustration, the models were fitted to the early part of the data (1926-1975) and the validity of the forecasting procedure was checked on data from the later period (1976-1993). Two procedures for evaluating the performance of the probability forecast are suggested. Furthermore, for the case where only a single event is available (i.e. either it is the first event in a cluster or an isolated event), we also forecast the probability of the event being a foreshock as a function of its geographic location. Then, the validity of the forecast is demonstrated in a similar manner. Finally, making use of the multi-element prediction formula, we show that the forecasting performance is enhanced by the joint use of the information in the location of the first event, and that in the subsequent interevent history in the cluster.     

Measurements of atmospheric hydroperoxides at a rural site in central Japan

Measurements of hydroperoxides (H₂O₂ and MHP) at ground level were made from 2012 to 2015 in Imizu City, Toyama Prefecture in central Japan. H₂O₂ and MHP concentrations ranged from 0.01 to 3.5 ppb and from below the level of detection (< 0.01 ppb) to 1.4 ppb, respectively. The concentrations of H₂O₂ and MHP were high in the summer and low in the winter. The H₂O₂ concentration was at its maximum in July and August, whereas the concentration of O₃ in the daytime was highest in May and June. The ratio of [H₂O₂]/[SO₂] presented clear seasonal variations. Many cases showed the condition of [H₂O₂] < [SO₂], called oxidant limitation especially in the cold months. Hydroperoxide concentrations in the rainwater were also high in the summer. The concentrations of MHP were much lower than those of H₂O₂ in the rain water. High concentrations of H₂O₂ (> 2.5 ppb) were detected in the summer during the inflow of air pollution. The concentrations of H₂O₂ were significantly high in July and August of 2013. The H₂O₂ was well correlated with the O₃ in July and August whereas there was no correlation between O₃ and H₂O₂ in May and June. There was a negative correlation between NO_X and H₂O₂.     

High-resolution shallow seismic and ground penetrating radar investigations revealing the evolution of the Uemachi Fault system, Osaka, Japan

Abstract Ground penetrating radar (GPR) and high‐resolution shallow reflection seismic surveying were carried out to investigate the subsurface geology in and around the Uemachi Fault zone in the Yamato River area, Osaka, Japan. Shallow drilling in the area showed a major displacement event during the middle Pleistocene. The main Uemachi Fault plane could be clearly imaged on the seismic section, except for the most shallow 200 m. Several shallow normal fault planes with less displacement could be detected on both sides of the fault plane. GPR profiles confirmed the presence of several shallow normal faults within the area near the fault zone. These shallow faults could be followed in all of the GPR profiles crossing the fault zone. The integration of seismic section, GPR profiles and drilling data led to a conceptual model that explains the evolution of the Uemachi Fault system. The proposed model suggests the occurrence of several cycles of small vertical displacement along the deep part of the fault plane caused by the regional east–west compressional stress. The ductile nature of the shallow sedimentary cover and the absence of confining pressure in the shallow part allow for a considerable amount of plastic bending before failing in the shallow sedimentary layers. This bending generates stretching force within the shallow sedimentary cover, which in time, along with gravitational force, gives rise to the formation of the swarm of normal faults within the shallow layers near the fault zone. Some of the detected faults extend to a depth of less than 3 m below the ground surface, suggesting that the last tectonic activity along the fault plane may have occurred recently.     

Correction to: Microtremor array method using spatial autocorrelation analysis of Rayleigh-wave data

Journal of Seismology -