Remote Response of an Electric Field and Atmospheric Current to Strong Earthquakes

Doklady Earth Sciences - The vertical component of the electric field strength and atmospheric current variations accompanying strong earthquakes with a magnitude of more than six are analyzed on...     

Geophysical Effects of the November 26, 2019, Earthquake in Albania

Doklady Earth Sciences - Based on instrumental observations made at a number of the INTERMAGNET network observatories, at the Mikhnevo Geophysical Observatory, and at the Center for Geophysical...     

Relationship between the Parameters of Infrasound Waves and the Energy of the Source

Izvestiya, Physics of the Solid Earth - Abstract—A new phenomenological model describing the propagation of acoustic disturbances in the stratospheric waveguide is proposed based on...     

Acoustic and Magnetic Effect of a Falling Bolide on November 17, 2021

Doklady Earth Sciences - The results of instrumental observations of acoustic oscillations and geomagnetic variations during the fall of the bolide on November 17, 2021, near the town of Izhevsk...     

Geophysical Effects of the Eruption of Hunga–Tonga–Hunga–Ha’apai Volcano on January 15, 2022

Doklady Earth Sciences - The results of instrumental observations for meteoparameters, microbaric variations, and variations in an electric field are analyzed at the Mikhnevo Observatory and the...     

Geochemistry and chronology of the Bunburra Rockhole ungrouped achondrite

Bunburra Rockhole is a unique basaltic achondrite that has many mineralogical and petrographic characteristics in common with the noncumulate eucrites, but differs in its oxygen isotope composition. Here, we report a study of the mineralogy, petrology, geochemistry, and chronology of Bunburra Rockhole to better understand the petrogenesis of this meteorite and compare it to the eucrites. The geochemistry of bulk samples and of pyroxene, plagioclase, and Ca‐phosphate in Bunburra Rockhole is similar to that of typical noncumulate eucrites. Chronological data for Bunburra Rockhole indicate early formation, followed by slow cooling and perhaps multiple subsequent heating events, which is also similar to some noncumulate eucrites. The ²⁶Al‐²⁶Mg extinct radionuclide chronometer was reset in Bunburra Rockhole after the complete decay of ²⁶Al, but a slight excess in the radiogenic ²⁶Mg in a bulk sample allows the determination of a model ²⁶Al‐²⁶Mg age that suggests formation of the parent melt for this meteorite from its source magma within the first ~3 Ma of the beginning of the solar system. The ²⁰⁷Pb‐²⁰⁶Pb absolute chronometer is also disturbed in Bunburra Rockhole minerals, but a whole‐rock isochron provides a re‐equilibration age of ~4.1 Ga, most likely caused by impact heating. The mineralogy, geochemistry, and chronology of Bunburra Rockhole demonstrate the similarities of this achondrite to the eucrites, and suggest that it formed from a parent melt with a composition similar to that for noncumulate eucrites and subsequently experienced a thermal history and evolution comparable to that of eucritic basalts. This implies the formation of multiple differentiated parent bodies in the early solar system that had nearly identical bulk elemental compositions and petrogenetic histories, but different oxygen isotope compositions inherited from the solar nebula.     

Rigidity of the fault zones in the Earth’s crust estimated from seismic data

Nonlinear effects in seismic wave propagation are analyzed to determine the mechanical rigidity of different-order faults that thread the tectonic structures in the central part of the East European platform (Moscow syneclise and Voronezh Crystalline Massif) and the fault zones of the Balapan and Degelen mountain regions in Kazakhstan (the Degelen magmatic node in the Central Chingiz zone). The dependency of the rigidity of the fault zone on the fault’s length is obtained. The rigidity of the tectonic structures is found to experience well-expressed temporal variations with periods of 13–15 days, 27–32 days, and about one year. In the different-order fault zones, the amplitudes of both normal k _n and the shear k _s rigidity for semimonthly, monthly, and annual variations can span a factor of 1.3, 1.5, and 2.5, respectively.