Estimating the Attenuation of Seismic Wave Energy at Short Distances from Kizimen Volcano, Kamchatka
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mating the Attenuation of Seismic Wave Energy at Short Distances from Kizimen Volcano, Kamchatka V. K. Lemzikova, † and M. V. Lemzikova, * aInstitute
of Volcanology and Seismology, Far East Branch, Russian Academy of Sciences, bulvar Piipa, 9, Petropavlovsk-Kamchatsky, 683006 Russia *e-mail: [email protected]
Received March 11, 2019; revised November 26, 2019; accepted March 31, 2020
Abstract—A swarm of volcanic earthquakes that occurred during an eruption of Kizimen Volcano provided an opportunity to study the attenuation of seismic wave energy in volcanogenic rocks at short hypocentral distances from the volcano. The study is based on P and S waves, as well as coda waves, using frequency dependent and frequency independent methods: pulse broadening, code normalization, and the model of single backscattering of coda waves. It is possible that further studies along these lines would also yield results for stress and strain in volcanogenic rocks beneath the volcano and in its cone. The determination of intrinsic absorption and scattering of seismic waves showed that the total attenuation within the volcanic edifice is dominated by shear wave scattering compared with intrinsic energy absorption. The conclusion is that the Q of the Kizimen volcanogenic rocks is higher than that of tectonic media. Keywords: Kizimen Volcano, volcano-tectonic earthquakes, seismic stations, pulse broadening, coda normalization, absorption, scattering DOI: 10.1134/S074204632004003X
INTRODUCTION Kizimen, an active volcano whose absolute altitude is 2485 m, shows eruptions of the effusive–explosive type. The first scientific studies of the volcano date back to the summer of 1943 (Piip, 1946). The volcano is situated on the southeastern side of the Shchapina Graben in the Kamchatka Peninsula. The Kizimen area with the adjacent Gamchen mountain range and the valley of the Levaya Shchapina River has a complex tectonics. The volcanic edifice is confined to the system of large-amplitude normal faults striking northeast where is the junction zone between the Shchapina Graben and the Tumrok horst (Kamchatka …, 1974). Kizimen has produced about ten eruptions during the last 200 years. The last but one eruption seems to have occurred in 1927–1928 (Gushchenko, 1979). A low-magnitude seismic activity began on Kizimen in the early 2009 and continued into 2010. The next explosive–effusive eruption began in December 2010 after a repose period of more than 80 years. The first seismic signals of the new eruption might provide evidence of explosions and debris avalanches on the volcano. They first appeared on December 9, 2010, while a sharp increase in seismic and volcanic activity started during the night between December 9 and 10 (local † Deceased.
time) (Senyukov et al., 2010). The eruption lasted 3 years, until the end of December 2013. Volcanogenic rocks are usually strongly heterogeneous. One notices the presence of lava flows, ashes, and complex-structured features within any predominant fault directions, etc. The surficial layers may contain bomb
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