About possibility to locate an EQ epicenter using parameters of ELF/ULF preseismic emission

A relation between parameters of preseismic ULF/ELF emissions and EQ is studied. The magnetic data measured at Karymshino station (Kamchatka, Russia) along with data on local seismic activity during eight years of observations (2001–2008) are taken for the analysis. Source azimuth is detected in different techniques, based on the analysis of the total field and its polarized pulsed component. The latter technique shows a better accuracy in the source azimuth detection. The errors of the method are associated with existence of non-seismic sources and with use of one-point observation. The second error can be eliminated by development of multi-point observations

Recurrence of Deep Long-Period Earthquakes beneath the Klyuchevskoi Volcano Group, Kamchatka

International audienceAbstract—Long-period earthquakes and tremors, on a par with volcano-tectonic earthquakes, are one of two main classes of volcano-seismic activity. It is believed that long-period volcanic seismicity is associated with pressure fluctuations in the magmatic and hydrothermal systems beneath volcanoes and can therefore be used as a precursor of the impending eruptions. At the same time, the physical mechanism of the long-period seismicity is still not fully understood. In this work, we have studied the long-period earthquakes that occur at the crust-mantle boundary beneath the Klyuchevskoi volcanic group in Kamchatka in order to establish their recurrence law—the relationship between the magnitude and frequency of occurrence of the events. In the region under study, the earthquakes pertaining to this type are most numerous and characterize the state of the deep magma reservoir located at the crust-mantle boundary. The changes in the seismic regime in this part of the magmatic system can be one of the early precursors of eruptions. For a more thorough characterization of the frequency-magnitude relationship of the discussed events, we compiled a new catalog of the deep long-period earthquakes based on the matched-filter processing of continuous seismograms recorded by the network stations of the Kamchatka Branch of the Geophysical Survey of the Russian Academy of Sciences in 2011-2012. For these earthquakes, we also used a magnitude determination method that provides the estimates close to the moment magnitude scale. The analysis of the obtained catalog containing more than 40 000 events shows that the frequency-magnitude relationships of the earthquakes markedly deviate from the Gutenberg-Richter power-law distribution, probably testifying to the seismicity mechanism and peculiarities of the sources that differ from the common tectonic earthquakes. It is shown that the magnitude distribution of the deep long-period earthquakes is, rather, described by the distributions with characteristic mean values such as the normal or gamma distribution

Detecting and locating volcanic tremors on the Klyuchevskoy group of volcanoes (Kamchatka) based on correlations of continuous seismic records

International audienceWe analyse daily cross-correlation computed from continuous records by permanent stations operating in vicinity of the Klyuchevskoy group of volcanoes (Kamchatka). Seismic waves generated by volcanic tremors are clearly seen on the cross-correlations between some pairs of stations as strong signals at frequencies between 0.2 and 2 Hz and with traveltimes typically shorter than those corresponding to interstation propagation. First, we develop a 2-D source-scanning algorithm based on summation of the envelops of cross-correlations to detect seismic tremors and to determine locations from which the strong seismic energy is continuously emitted. In an alternative approach, we explore the distinctive character of the cross-correlation waveforms corresponding to tremors emitted by different volcanoes and develop a phase-matching method for detecting volcanic tremors. Application of these methods allows us to detect and to distinguish tremors generated by the Klyuchevskoy and the Tolbachik, volcanoes and to monitor evolution of their intensity in time

Physics of Auroral Phenomena

Abstract Spectral and polarization parameters of the natural ULF/ELF signal in a seismic region (Kamchatka, Russia) are statistically analyzed and a meaningful change in the signal polarization is found to occur several days prior powerful earthquakes (EQ). This effect can be caused by an extended thunderstorm activity in the EQ preparation zone due to either aerosol and gas emissions by an active fault or by the modification of the ionosphere by the preseismic AGW waves

The largest deep-focus Sea of Okhotsk earthquake May 24, 2013, Mw=8.3

This is the second part of an report of Chebrov et al. on notable events in Kamchatka in 2013 for the Summary of the Bulletin of the International Seismological Centre including the largest deep-focus Sea of Okhotsk earthquake from 24 May 2013 with a magnitude of Mw=8.3