*GEOPHYSICAL RESEARCH, 2016, vol.17, no.3, pp. 45-59.* **DOI: 10.21455/gr2016.3-4**

*UDC 550.34, 551.21*

**Abstract References**** Full text (in Russian) Full text (in English)**

**FORMALIZED TECHNIQUE OF BEZYMIANNY VOLCANO (KAMCHATKA) ERUPTION FORECASTING BASED ON THE STATISTICAL ESTIMATION ****OF SEISMICITY LEVEL**

*Kamchatka Branch of Geophysical Survey of RAS, Petropavlovsk-Kamchatsky, Russia*

**Abstract.** The paper proposes a formalized technique of probabilistic forecast by applying statistical estimation of seismicity level and a number of additional functions that characterize the predictive situation. The possibilities of this method are illustrated by the example of seismic activation before the eruptions of the Bezymianny Volcano (Klyuchevskaya group, Kamchatka).

The initial data is the catalog of earthquakes of the Klyuchevskaya group of volcanoes during 1999-2014, compiled by the Kamchatka Branch of the Geophysical Survey, RAS. During this time there were 21 eruptions of the Bezymianny Volcano. The precursor is defined as a threshold function associated with the current seismicity level and its characteristic form before the eruption.

The values of parameters characterizing the precursor are given including validity, reliability and efficiency, calculated by two methods. It is shown that the reliability of the precursor decreases with the increase in threshold values, and its validity increases.

The reliability of the method is 0.38 – 0.95, i.e., from 38% to 95% of eruptions had the precursor depending on the threshold level; and the validity is 0.3 – 0.6, i.e., from 30% to 60% of the identified precursors are realized also depending on the threshold level. Values of efficiency confirm the non-random nature of the precursor appearance.

The method includes determination of the probability of the forecast realization. The nomogram for probabilities depending on the duration of the forecast and the values of the prognostic parameter is designed.

**Keywords:** precursor, forecasting, earthquake, eruption, Kamchatka, Bezymianny Volcano.

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