On the correlation between ionospheric perturbations as detected by subionospheric VLF/LF signals and earthquakes as characterized by seismic intensity

The long-term data during seven years from January 2001 to December 2007, as observed by the Pacific VLF/LF network consisting of several Japanese stations and one station in Kamchatka, are extensively utilized to perform a statistical correlation study between the lower ionospheric perturbations as detected by subionospheric propagation and earthquakes (EQs). In this paper, we adopt a physical parameter, the maximum seismicity intensity observed (I) to define the strength of an EQ unlike the previously and conventionally used EQ magnitude and depth, which is a combined effect of EQ magnitude and depth, together with the Earth’s surface information and geological condition around the EQ epicenter. After considering EQs only take place on the land because of the use of seismicity and by using the superimposed epoch analysis, it is found for the larger EQs with I from 5 to 7 (we feel serious trembling and we expect serious damage) that the most important VLF/LF parameter, trend (nighttime average amplitude), shows a definite decrease about 10 days before the EQ by exceeding 2σ (σ: standard deviation) criterion; the dispersion shows a maximum about 10 days before the EQ but not exceeding 2σ line and finally the nighttime fluctuation shows an enhancement about 10 days before the EQ (with exceeding the 2σ level). A definite statistical correlation is confirmed between the ionospheric perturbations and I when I is strong enough in a range from 5 to 7. Whereas, there is no significant correlation between the two when I is in a range from 3 to 4. Finally, together with the corresponding results for EQs in the sea, but close to the land, these results are discussed in the light of lithosphere–ionosphere coupling mechanism.     

Variations in the parameters of VLF signals on the DEMETER satellite during the periods of seismic activity

Two methods for diagnosing ionospheric disturbances using VLF signals received on the DEMETER satellite are considered in connection with two cases of high seismic activity: the method for analyzing a signal reception zone in order to find large-scale spatial variations and the residual signal method used to reveal time variations. Based on an analysis of the VLF signal reception zone, performed in connection with the catastrophic earthquake near Sumatra, it has been found out that the signal amplitude decreased during a month before the earthquake. As a result, it has been concluded that the zone of ionospheric disturbances extends for several thousand kilometers. It has been indicated that the residual signal method showed good agreement between the ground and satellite data when high seismic activity near Japan was analyzed.     

Model estimates of the eutrophication of the Baltic Sea in the contemporary and future climate

The St. Petersburg Baltic eutrophication model (SPBEM) is used to assess the ecological condition of the sea under possible changes in climate and nutrient loads in the 21st century. According to model estimates, in the future climate water quality will worsen, compared to modern conditions. This deterioration is stronger in the climate warming scenario with a stronger change in future near-surface air temperature. In the considered scenarios of climate change, climate warming will lead to an increase in the area of anoxic and hypoxic zones. Reduction of nutrient loading, estimated in accordance with the Baltic Sea Action Plan, will only be able to partially compensate for the negative effects of global warming.     

Gold-Plationoid Mineralization of Metasomatically Altered Ultramafites in Precambrian Protrusions of Mamynsky Geoblok

On the contiguous territories of Russia and China, along the left and right banks of the Amur River (Heilongjiang Province of China, and Amur Oblast′ of Russia), several Precambrian protrusions (Gonzhinsk, Mamynsk, Amurkhe, and Khumakhe) are known. On the Russian territory, along the setting and on the area of the protrusions, lode manifestations, precious-metal deposits, and gold-platinoid placers are known having the industrial imponance. Ultramafites are metasomatically altered more likely by the action of the kate Paleozoic intrusions and produced by them hydrothermae, and are transformed into listvenites. It can be concluded that as one of the sources of precious metals in the placers were the aureoles of listvenitization. This is evidenced by the presence of talc (typomorphic mineral of apoultrabasites) inclusions together with Pt-, Pd- and Ir-bearing gold in the corrosive coatings of the primary platinoids. This conclusion requires the revision of the work strategy of prospecting the lode gold and PGE manifestations within the ore-placer node because apoultrabasites before were considered non-promising for precious metals.     

First Finds of Native Gold and Platinum in the Ilmenite Placers of the Ariadnoye Basite–Ultrabasite Intrusion (Primorye)

Doklady Earth Sciences - The basic features of mineralogy and geochemistry of the gold-ilmenite placers, which are spatially and genetically associated with the Ariadnoye intrusion of ultrabasites...     

First Data on Noble Metal–Rare Earth Mineralization in Graphite-Bearing Rocks of the Northern Margin of the Khanka Terrain

High-carbon rocks at the northern margin of the Khanka terrane (Primorskii krai) have been found to host new occurrences of noble and rare-earth metals: the largest of them is the Filinskoye deposit. The graphite ores, hosting copper-bearing high-grade gold, silver, monazite, xenotime, sulfides, rutile, barite, and uraninite, demonstrate high ties of carbon with gold and rare earths. The graphite demonstrates δ¹³C from–2.1 to–5.5‰, corresponding to the mantle isotope composition. This suggests that the primary sources of the ore-forming system were deep carbon-bearing fluids.