Sector collapses and large landslides on Late Pleistocene–Holocene volcanoes in Kamchatka, Russia (2006)
Ponomareva Vera V., Melekestsev Ivan V., Dirksen Oleg V. Sector collapses and large landslides on Late Pleistocene–Holocene volcanoes in Kamchatka, Russia // Journal of Volcanology and Geothermal Research. 2006. Vol. 158. № 1-2. P. 117-138. doi:10.1016/j.jvolgeores.2006.04.016.
Аннотация
On Kamchatka, detailed geologic and geomorphologic mapping of young volcanic terrains and observations on historical eruptions reveal that landslides of various scales, from small (0.001 km3) to catastrophic (up to 20–30 km3), are widespread. Moreover, these processes are among the most effective and most rapid geomorphic agents. Of 30 recently active Kamchatka volcanoes, at least 18 have experienced sector collapses, some of them repetitively. The largest sector collapses identified so far on Kamchatka volcanoes, with volumes of 20–30 km3 of resulting debris-avalanche deposits, occurred at Shiveluch and Avachinsky volcanoes in the Late Pleistocene. During the last 10,000 yr the most voluminous sector collapses have occurred on extinct Kamen' (4–6 km3) and active Kambalny (5–10 km3) volcanoes. The largest number of repetitive debris avalanches (> 10 during just the Holocene) has occurred at Shiveluch volcano. Landslides from the volcanoes cut by ring-faults of the large collapse calderas were ubiquitous. Large failures have happened on both mafic and silicic volcanoes, mostly related to volcanic activity. Orientation of collapse craters is controlled by local tectonic stress fields rather than regional fault systems.
Specific features of some debris avalanche deposits are toreva blocks — huge almost intact fragments of volcanic edifices involved in the failure; some have been erroneously mapped as individual volcanoes. One of the largest toreva blocks is Mt. Monastyr' — a ∼ 2 km3 piece of Avachinsky Somma involved in a major sector collapse 30–40 ka BP.
Long-term forecast of sector collapses on Kliuchevskoi, Koriaksky, Young Cone of Avachinsky and some other volcanoes highlights the importance of closer studies of their structure and stability.
Seismic tomography of the Pacific slab edge under Kamchatka (2009)
Jiang Guoming, Zhao Dapeng, Zhang Guibin Seismic tomography of the Pacific slab edge under Kamchatka // Tectonophysics. 2009. Vol. 465. № 1–4. P. 190 - 203. doi: 10.1016/j.tecto.2008.11.019.
Аннотация
We determine a 3-D P-wave velocity structure of the mantle down to 700 km depth under the Kamchatka peninsula using 678 P-wave arrival times collected from digital seismograms of 75 teleseismic events recorded by 15 portable seismic stations and 1 permanent station in Kamchatka. The subducting Pacific slab is imaged clearly that is visible in the upper mantle and extends below the 660-km discontinuity under southern Kamchatka, while it shortens toward the north and terminates near the Aleutian–Kamchatka junction. Low-velocity anomalies are visible beneath northern Kamchatka and under the junction, which are interpreted as asthenospheric flow. A gap model without remnant slab fragment is proposed to interpret the main feature of high-V anomalies. Combining our tomographic results with other geological and geophysical evidences, we consider that the slab loss may be induced by the friction with surrounding asthenosphere as the Pacific plate rotated clockwise at about 30 Ma ago, and then it was enlarged by the slab-edge pinch-off by the asthenospheric flow and the presence of Meiji seamounts. As a result, the slab loss and the subducted Meiji seamounts have jointly caused the Pacific plate to subduct under Kamchatka with a lower dip angle near the junction, which made the Sheveluch and Klyuchevskoy volcanoes shift westward.
Seismicity and source parameters of earthquakes in the region of the large Tolbachik fissure eruption (1982)
Zobin V.M., Gorelchik V.I. Seismicity and source parameters of earthquakes in the region of the large Tolbachik fissure eruption // Bulletin Volcanologique. 1982. Vol. 45. Vol. 2. P. 99-113. 15 p. doi:10.1007/BF02600427.
Seismicity observed during the precursory process and the actual eruption of Kizimen Volcano, Kamchatka in 2009-2013 (2014)
Firstov P.P., Shakirova A.A. Seismicity observed during the precursory process and the actual eruption of Kizimen Volcano, Kamchatka in 2009-2013 // Journal of Volcanology and Seismology. 2014. Vol. 8. № 4. P. 203-217. doi: 10.1134/S0742046314040022.
Аннотация
Seismological Studies on the Mechanism of the Large Tolbachik Fissure Eruption, 1975-1976 (1980)
Fedotov S.A., Gorelchik V.I., Stepanov V.V. Seismological Studies on the Mechanism of the Large Tolbachik Fissure Eruption, 1975-1976 // Bulletin Volcanologique. 1980. Vol. 43. Vol. 1. P. 73-84. doi: 10.1007/BF02597612.
Аннотация
Seismological observations provided consistent information on the course and mechanism of the complicated large fissure eruption at Tolbachik volcano in Kamchatka from July 6, 1975 to December 10, 1976. Seismicity indicates that the initial magnesian basalts were rising ten days before the eruption from depths of more than 20 km. The formation of new feeding dykes was accompanied by earthquake swarms which decreased sharply one to two days before the opening of new eruptive fissures. The seismological data indicate that the main source of the different erupted basalts (2 km) was a vast system (diameter ca. 80 km) of hydraulically connected magma
chambers located in the lower crustal layers or in the crust-mantle transition layer.
Shiveluch volcano: seismicity, deep structure and forecasting eruptions (Kamchatka) (1997)
Gorelchik V.I., Shirokov V.A., Firstov P.P., Chubarova O.S. Shiveluch volcano: seismicity, deep structure and forecasting eruptions (Kamchatka) // Journal of Volcanology and Geothermal Research. 1997. Vol. 78. № 1–2. P. 121 - 137. doi: 10.1016/S0377-0273(96)00108-4.
Аннотация
The deep structure, Wadati-Benioff zone (focal zone) geometry and the magma feeding system of Shiveluch volcano are investigated based on 1962–1994 detailed seismic surveillance. A focal zone beneath Shiveluch is dipping at an angle of 70° at depths of 100–200 km. Based on the revealed interrelations between seismicity at depths of 105–120 km and an extrusive phase of its eruptions in 1980 through 1994, it is inferred that primary magmas, periodically feeding the crustal chamber, are melted at depths of at least 100 km. An upsurge of extrusive-explosive activity at the volcano is preceded and accompanied by the increasing number and energy of both volcanic earthquakes beneath the dome and tectonic or volcano-tectonic earthquakes in the zones of NW-striking crustal faults near the volcano.The eruption of April 1993 has been the most powerful since 1964. It was successfully predicted based on interactive use of all seismic data. At the same time the influence of seismicity at depths of 105–120 km under the volcano on the style (and consequently on prediction) of its activity is decisive.
Small but important: new data about activity and composition of Zarechny volcano (Central Kamchatka depression) (2018)
Gorbach N.V., Ponomareva V.V., Pendea I. Florin, Portnyagin M.V. Small but important: new data about activity and composition of Zarechny volcano (Central Kamchatka depression) // 10th Biennual workshop on Japan-Kamchatka-Alaska subduction processes (JKASP-2018). Petropavlovsk-Kamchatsky, Russia, August 20-26. 2018. P. 83-85.