No 1 (2019)

Asymmetrical seismic pulses before a large earthquake
Sobolev G.A., Zakrzhevskaya N.A., Kireenkova S.M.

This study is concerned with the behavior of seismic noise in the period range of a few minutes based on records made by broadband IRIS stations before the catastrophic earthquake of March 11, 2011 in Japan. A formalized technique was used to identify discrete asymmetrical pulses whose amplitudes were an order of magnitude higher than the noise level and that were spaced at intervals longer than 30 minutes. The frequency of pulses at the MAJO station on Honshu 400 km of the earthquake epicenter increased on January 30, 2011 and remained high until March 2, 2011. No such phenomena have been observed at MAJO in the same periods during the preceding 15 years, when the station was in regular operation. The records of other similar stations farther than 1700 km from the epicenter were not found to contain increases in the rate of pulses. We believe that these asymmetrical pulses were due to dilatancy in shallow crustal layers beneath the MAJO station.

Вулканология и сейсмология. 2019;(1):3-13
Earth’s surface deformation on mount Etna: GPS measurements, interpretation, relationship to the mode of volcanism
Kafta V.I., Rodkin M.V.

We present results from a study of lateral Earth’s surface deformation and vertical movements in the area of the Mount Etna active volcano (Sicily, Italy) based on observations by global satellite navigation systems in 2011–2017 at time intervals of 24 hours at sparse stations of the regional geodetic network. The study of Mount Etna is especially important because (1) the volcano stands in a densely populated area, (2) the eruptions are nearly continuous, and (3) the location of the volcano is inconsistent with plate tectonic concepts. Subregional trends have been identified in the deformation of the area of study. Extension was recorded, not only around the summit crater, but also far from it, in the Ionian Sea. This circumstance suggests the existence of an extensive plumbing system at depth whose sources are far from the active summit crater. We discuss geological and geophysical survey results of the coastal area and the sea area in the region. It is shown that Earth’s surface deformation should be studied from observations of the existing networks that are sparse, but cover a large area.

Вулканология и сейсмология. 2019;(1):14-24
Volcanology and new geophysics: reality and prospects for example Yellowstone volcano
Khavroshkin O.B., Fedotov S.A., Tsyplakov V.V., Boiko A.N.

The dynamic portrait of Yellowstone volcano activity in the form of detailed analysis of key parameters and in real time is presented. Some preliminary findings show that active volcanoes are energetically open systems with a strong influence of the external astrophysical component, primarily solar muon and neutrino fluxes. This should be taken into account when predicting their activity. The astrophysical component of activity may be one of the main mechanisms synchronizing the state of supervolcanoes. The astrophysical component of volcanic activity can exist in other volcanoes of the terrestrial planets of the Solar system, which also experience the synchronizing effects of the solar neutrino flux, that is, the planets of the Solar system can be found to have common rhythms of volcanic activity.

Вулканология и сейсмология. 2019;(1):25-35
The present-day seismicity of the White Sea region
Morozov A.N., Vaganova N.V., Asming V.E., Nikonov A.A., Sharov N.V., Konechnaya Y.V., Mikhailova Y.A., Evtyukhina Z.A.

A revised earthquake catalog has been compiled for the White Sea region for the period between 2005 and 2016. The earthquake parameters were revised using a single velocity model (BARENTS), a single methodological approach (Generalized Beamforming), and all available raw data and bulletins of Russian and foreign seismic stations. The location of two nuclear explosions detonated on July 18, 1985 and September 6, 1988 in northern European Russia for civilian purposes showed that the algorithm for calculating hypocenter parameters combined with the BARENTS velocity model is an effective tool. The resulting earthquake catalog enabled us to reveal the leading patterns in the distribution of recent seismicity in the White Sea region.

Вулканология и сейсмология. 2019;(1):36-51
The predictability of seismicity and large earthquakes: Kamchatka 1962 to 2014
Malyshev A.I.

This paper reports the estimation of the predictability of seismicity and large earthquakes in Kamchatka as inferred from data in the Kamchatka regional catalog for 1962–2014. The mathematical model uses a second-order nonlinear differential equation, while the optimization algorithm and the estimates of predictability are the author’s own. The estimates show a high predictability of seismicity; the extrema of prediction nonlinearity typical of large earthquakes usually occur simultaneously with similar extrema of seismicity as a whole. Overall, 220 large (K ≥ 13.3) Kamchatka earthquakes were analyzed to find that foreshock predictability was available for 200 earthquakes (~30000 determinations) and aftershock predictability for 215 earthquakes (~300000 determinations). The predictability related to large earthquakes began to be seen and was rapidly increasing at intermediate (7.5–30 km) radii of hypocenter samples. The prediction distances over time were some tens and hundreds of days for foreshock predictability and some hundreds and thousands of days for aftershock predictability. These results demonstrate very good promise for the approximation extrapolation approach to the prediction of both large earthquakes themselves and of subsequent aftershock decay of seismic activity.

Вулканология и сейсмология. 2019;(1):52-66
A quantitative estimate of the effects of sea tides on aftershock activity: Kamchatka
Baranov A.A., Baranov S.V., Shebalin P.N.

The issue of whether tidal forces really affect seismicity has been raised many times in the literature. Nevertheless, even though there seems to be a kind of consensus that such effects do exist, no quantitative estimates are available to relate tide parameters to changes in the level of seismic activity. Such estimation for aftershocks of large earthquakes near Kamchatka is the goal of the present study. We consider the influence on seismicity due to ocean tides only, because their effects are stronger than those of solid earth tides. Accordingly, we only consider earthquakes that occurred in the ocean. One important feature that distinguishes the present study from most other such research consists in the fact that we study the height of ocean tides and its derivative rather than tidal phases as the decisive factors. We considered 16 aftershock sequences of earthquakes near Kamchatka with magnitudes of 6 or greater. We also examined shallow background earthquakes along the coast of Kamchatka. Our basic model of aftershock rate was the Omori–Utsu law. The background seismicity distribution was assumed to be uniform over time. In both of these cases we used the actual distributions in space. The heights of ocean tides were estimated using the FES 2004 model (Lyard et al., 2006). The variation in activity from what the basic model assumes in relation to tidal wave height and its time derivative was estimated by the method of differential probability gain. The main practical result of this study consists in estimates of averaged differential probability gain functions for aftershock rate with respect to both of theconsidered factors. These estimates can be used for earthquake hazard assessment from aftershocks with ocean tides incorporated. The results of our analysis show a persistent tendency of aftershock rate increasing during periods when the ocean tide decreased at a high rate. For the background events, we found a typical tendency of event rate increasing when the ocean tide decreased with high tidal amplitudes. The difference in the main factors that affect aftershocks and background seismicity suggest the inference that the effects of tides on aftershocks are more likely to be direct dynamic initiation of events during high strain rates, while the effects on the backgroundevents were static in character.

Вулканология и сейсмология. 2019;(1):67-82

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