Дата публикации: 24 ноября 2021
Автор(ы): Sergei SENYUKOV →
Публикатор: Научная библиотека Порталус
Рубрика: ЭКОЛОГИЯ →
Источник: (c) Science in Russia, №6, 2014, C.67-75 →
Номер публикации: №1637750468
Sergei SENYUKOV, (c)
by Sergei SENYUKOV, Cand. Sc. (Geol. & Mineral.), Head of the Laboratory for Seismic and Volcanic Activity Research of the Kamchatka Branch of the RAS Geophysical Service (Petropavlovsk-Kamchatsky)
Lying in the transition zone between the Asian continent and the Pacific Ocean at the intersection of the Kuril-Kamchatka and Aleutian Island Arcs, Kamchatka is among the regions of high seismic, volcanic and geodynamic activity, and is considered one of the most seismically active regions on the globe. It is there that about one third of all earthquakes registered in Russia occur; this peninsula is known for tsunamis and 29 active volcanoes, including Klyuchevskaya and Shiveluch, among the greatest on the Earth. That is why Kamchatka has become a major research ground for seismic studies with scientists engaged in the monitoring and forecasting of natural disasters caused by plutonic forces, and working to minimize the possible aftermath.
Flowing lava in the crater of Klyuchevskaya, September 23, 2010.
Photo, Yu. Demyanchuk
Bezymyanny ash emission height correlation schedule:
A - vs. absolute speed integral;
B - vs. speed square integral.
9 seismic events registered by the LGN station in the course of visual, photo and video monitoring analyzed.
Shiveluch ash emission vs. absolute speed integral for the SVL station correlation schedule for 255 seismic events registered in the course of visual, photo and video monitoring in 1999-2004.
HISTORY, EVENTS, PEOPLE
The first seismic station on Kamchatka was set up in 1915 on the initiative of Prince Boris Golitsyn, member of HM Academy of Sciences. In 1917, because of global devastation and absence of photographs, that station actually ceased its operation; and so earthquakes of the 1920s were monitored only by remote seismic centers of this and other countries.
In 1935, in the Klyuchi settlement close to the highly active Klyuchevskaya group of volcanoes*, the national Academy of Sciences founded a Kamchatka volcanic station. In 1944-1945 it was reorganized into a Laboratory of Volcanology which employed many qualified specialists and scientists expert in the earth sciences: Academician Alexander Zavaritsky; Vladimir Vlodav-
*The Klyuchevskaya group of volcanoes is located at the intersection of two island arcs-Kuril-Kamchatka and Aleutian Island Arcs; it incorporates 14 volcanoes: Klyuchevskaya (4,835 m), Kamen (4,575 m), Ushkovsky (4,108 m), Krestovsky (3,943 m), Ostry Tolbachik (3,682 m), Plosky Tolbachik (3,085 m), Bezymyanny (2,900 m), Ovalnaya Zimina (3,081 m), Ostraya Zimina (2,744 m), Bolshaya Udina (2,943 m), Malaya Udina (1,945 m), Srednyaya (2,990 m), Zarechny, and Kharchnsky-Ed.
ets, Dr. Sc. (Geol. & Mineral.); Academy of Sciences Corresponding Member Boris Piyp, among others. They realized that seismic and geophysical research methods were essential for studying underground processes as well as volcanic activity. And so, in 1946 the Klyuchi seismic station was put into service to monitor such active volcanoes as Klyuchevskaya, Shiveluch, and Tolbachik. In 1948-1956, this work was headed by Corresponding Member of the Science Academy Georgi Gorshkov, and in 1957-1963-by Pavel Tokarev, Cand. Sc. (Phys. & Math.).
In those days our scientists obtained fundamental results in seismology*. Gorshkov was the first to discover mantle roots of volcanoes. In the early 1950s, while studying records of earthquakes, he noted the abnormal absorption of secondary seismic waves under Klyuchevskaya, and concluded there was a magma pocket below the volcano 60-80 km deep. These observations
* See: G. Karpov, "Kamchatka, a Unique Region", Science in Russia, No. 6, 2010 - Ed.
Network of telemetric seismic stations and active volcanoes.
Volcano code and name:
SL - Shiveluch,
KL - Klyuchevskaya,
US - Ushkovsky,
BZ - Bezymyanny,
TL - Plosky Tolbachik,
IH - lchinsky,
KZ - Kizimen,
GM - Gamchen,
KC - Kronotsky,
KR - Krasheninnikova,
KH - Kikhpinych,
UZ - Uzon,
BS - Bolshoi Semyachik,
MS - MalySemyachik,
Kl - Karymsky,
DZ - Dzenzur,
JP - Zhupanovsky,
KK - Koryaksky,
AV - Avachinsky,
GR - Gorely,
MT - Mutnovsky,
OP - Opala,
KS - Ksudach,
JL - Zheltovsky,
IL - llyinsky,
KO - Koshelevsky,
KB - Kambalny.
excited much interest globally. In 1956, when the Bezy-myanny volcano erupted (a disastrous eruption it was), Gorshkov organized detailed volcanic studies of the erupting giant. After that a new term, the directed volcanic explosion was introduced to the earth sciences. All that made it possible to interpret devastating underground processes in a new way.
* See: O. Kondratyev, "New Paradigm of Earthquake Prognostication", Science in Russia, No. 4, 2000; V. Muravyov, G. Krasnopevtseva, "Violent Earthquakes: How Predictable?", Science in Russia, No. 6, 2000; V. Morgunov, " Earthquake Forecasts for Tomorrow", Science in Russia, No. 1, 2004.-Ed.
Pavel Tokarev, another volcanologist, has great achievements in volcanic studies to his credit*. He developed a method that allowed to forecast, for example, bursts of volcanic activity of the Bezymyanny (1958, 1959, 1960) and Shiveluch (1964) volcanoes. Tokarev is the author of the first national monograph on volcanology The Eruptions and Seismic Settings of the Klyuchevskaya Group of Volcanoes (1966). Thanks to this work its author became a top specialist in his field of research, volcanology. In 1975, the Large Tolbachik eruption took place in the Kuril-Kamchatka Volcanic
Belt. This eruption, its place and duration, was forecast by Tokarev.
Later on, two more volcanic stations near the Kly-uchevskaya group of volcanoes, Kozyrevsk (1958) and Apakhonchich (1960), were set up as part of the Kamchatka regional network formed in 1961 by the Pacific Seismic Station of the Geophysics Institute. By the end of 1962, the network had incorporated 10 research stations, and by 1971-as many as fifteen. In 1972 this network was placed under the supervision of the Institute of Volcanology (Far Eastern Research Center of the national Academy of Sciences).
Between 1979 and 1997, the monitoring work in Kamchatka was carried out by a field seismic division of the Institute of Volcanology, and in 1997 to 2004, it became the responsibility of the RAS Geophysical Service (in 2005, the Kamchatka Branch of the RAS Geophysical Service).
Since 2000 our specialists have been monitoring volcanic activity in real time. Video and visual monitoring on the peninsula is often hampered by bad weather, darkness (75 percent of time) or remote location of volcanoes from residential communities. Space monitoring of the territory is carried out irrespective of weather and light conditions. However, satellite data are haphazard and become available with a delay (~30 min, 2 hours on the average), and therefore it is not possible to determine a start-out time of an eruption. Seismic monitoring is
different, though: it is the main research method enabling 24 hour control of the situation in real time.
The Kamchatka Branch of the RAS Geophysical Service collects and processes seismic information with the aim of predicting volcanic activity. Urgent messages on potential hazards are sent to the Main Department of the Emergencies Ministry for the Kamchatka Territory, Dust Cloud Control Centers in Tokyo and Anchorage, Alaska Volcano Observatory (USA), as well as the Kamchatka Volcanic Eruption Response Team (KVERT) of the RAS Institute of Volcanology and Seismology (Far Eastern Branch) created in 1993. Ever since the KVERT has sent over 1,000 messages on the activity of Kamchatka volcanoes to major airlines, volcano observatories and weather services.
The radiotelemetric network of the Geological Service monitors seismic activity on different levels. Detail monitoring is performed on Avachinsky and Klyuchevs-kaya group of volcanoes, including Kizimen, Gorely, and Mutnovsky volcanoes. The volcanic activity of the smoking mountains Karymsky, Alaid (Atlasov Island) and Ebeko (Paramushir Island) is monitored by a station on each mountain, making it possible to record minor local tremors (however, without positioning). As for the other volcanoes, only powerful underground waves are registered using remote seismic stations.
In 1996-1998 a new digital signal recording system and data processing software were commissioned, which led to a quantum jump in the seismic science. In addition, an integral telemetric network with a realtime access was created. The new technologies boosted
the representative energy class (i.e. the quantitative value varying in the range of 0 to 18-20)*of registered earthquakes by 1 unit. Scientists are now able to register even weaker shocks in the regions of volcanic activity.
Data on all earthquakes, including their key parameters, recorded by three stations and more as well as seismic reviews of Kamchatka volcanoes are published in the annual bulletins issued by the RAS Geophysical Service.
ASSESSMENT OF SEISMIC ACTIVITY AND PROGNOSIS
There are two types of seismic activity-background (normal) and increased activity-identified by the number of earthquakes, their distribution in time and space, their energy released, and the spectral composition of signals, and other parameters. The background level means no ash emissions or white-hot lava flows. The other type, that of abnormal seismic activity, means that a "fire-breathing" mountain is not quiet. In this case, a volcanic hazard alert system in the form of a four-color code scale is activated. It was first used by the Alaska Volcano Observatory to mark the threat level for aviation. The color code (green, yellow, orange or red) depending on the seismic activity level registered daily proved a good supplement to the system. Thus volcanic seismic activity can be assessed in real time. By collecting, accumulating and studying recorded data, scientists can make a forecast-an official docu-
* See: "Energy of Volcanoes", Science in Russia, No. 1, 2006.-Ed.
ment specifying the type of an eruption, its scale, start-out time, duration, and threat to the population. The forecast is then submitted to the Kamchatka Branch of the Russian Expert Council for Forecasting and Assessment of Seismic Risks and Threats.
The first official forecast was sent to the Kamchatka Branch of the Russian Expert Council in January 2005. By 2013 we had gained sufficient experience to make a reliable assessment of seismic status of Bezymyanny and Klyuchevskaya volcanoes. We forecast 10 out of 12 explosive eruptions of Bezymyanny (one alarm false), and made 3 reliable mid-term forecasts of the seismic dynamics of Kluchevskaya (out of 4 eruptions) in a period from 2005 to 2012.
The problem of timely notification of emergency services on the place, time, and height of an ash emission in realtime irrespective of weather and light conditions is still a live issue. It should be solved above all to guarantee air flight safety. If automated, this notification system will speed up and facilitate operators' work.
In 2003 the Laboratory for Seismic and Volcanic Activity Research of the Kamchatka Branch of the RAS Geophysical Service implemented an original empiric method of ash emission detection and assessment. Relevant seismic signals are picked out by spectral analysis, and the height of emission is assessed by an absolute speed integral (software developer-Dmitry Droznin, a lead expert). The laboratory has created a database of video, photo and visual observations of ash emis-
sions and concomitant seismic signals for active Kamchatka volcanoes. For example, over 350 emissions have been recorded on Shiveluch, over 100-on Karymsky, over 20-on Kizimen, and 9 emissions on Bezymyanny.
Since 2012 work has been under way to automate the data management procedure; it had the first run (author-Vitaly Bliznetsov) the same year. The program uses the frequency index Fl equal to the common logarithm log(Au/Al), where Au is the signal amplitude in a high-frequency band and Al is the signal amplitude in a low-frequency band. A continuous seismic record is split in frequency bands by the SWAN program (author, Dmitry Droznin).
The empiric method was tested on four active volcanoes (Shiveluch, Karymsky, Bezymyanny, and Kizimen), and it was a success. Our experience shows: accuracy of height calculations based on seismic data is about 30 percent of the height and is comparable to the satellite data. From 2001 till 2011, the new data management system made it possible to send over 680 urgent messages within the international KVERT project on ash emissions dangerous to air flights.
FIERY BREATH OF THE PENINSULA
What has been happening to Kamchatka volcanoes in recent years? According to the Geological Service, there are 9 active volcanoes in the region: Karymsky, Plosky Tolbachik, Shiveluch, Klyuchevskoy, Mutnovs-ky, Zhupanovsky, Gorely, Bezymyanny, and Kizimen.
Powerful ash emissions have been registered recently on Shiveluch-the northernmost of the active giants located in the Ust-Kamchatsky district. It woke up on December 4, 2006, after a silent year. Its eruptions are in the active, though irregular, phase; there are several eruptions each year. In active periods the height of ash emissions can reach 10 km above sea level. Then come quiet days, and the giant is asleep for a few weeks. The cycle repeats over and over again. The volcano has been persisting in this state for as long as 8 years. And it will keep up like that.
The eruption of Plosky Tolbachik volcano located in the same Ust-Kamchatsky district that started on November 27, 2012, with the formation of a giant fracture 5 km long, is certainly grand. The volcano had been silent for 36 years. Two lava emission centers (with the temperature about 1,000 °C) were formed on its slope. One lava flow ran over 6 km, the other-over 15 km. The area of lava streams erupted in the first days can be compared to that of Elizarovo, the second largest town in Kamchatka. This fracture eruption was dedicated to the 50th jubilee of the Institute of Volcanology and Seismology. In April 2013 the underground activity of Plosky Tolbachik slackened somewhat, and on August 23 the violent eruption phase came to an end. According to our data, the fire-breathing mountain is unlikely to regain its power soon.
Located in the center of the Klyuchevskaya group of volcanoes 350 km northwest of Petropavlovsk-Kam-chatsky, the Bezymyanny volcano had kept silent for a
thousand years, it was considered dead up until 1955. Its first eruption in recent history began in October of 1955. On March 30, 1956, a powerful explosion blew off the top of the volcano (it became 30 m lower) and changed the ambient environment. After that the volcano erupted once or twice a year with its ash rising 6 to 15 km above sea level.
In 2004 our laboratory specialists developed the first prediction algorithm for the volcano's activity based on seismic and space data. This algorithm was used in a period from 2005 to 2010, making it possible to forecast 7 middle-range explosive eruptions out of 9 recorded events, with one false alarm. The updated algorithm enabled us to forecast the eruptions of the volcano that took place on April 13, 2011, then on March 8, 2012, and on September 1, 2012. No false alarms!
Klyuchevskaya is the highest (~4,750 m) and the most powerful basalt volcano of the Kuril-Kamchatka Region. In 2000-2010 five long eruptions accompanied by ash emissions and lava flows were registered in the central crater of the volcano. All these events have one thing in common: the eruption developed gradually, and that is why forecasts for Bezymyanny were most important (outbursts were sudden and powerful). The collected data and their assessment made it possible to make three mid-term forecasts for Klyuchevskaya (4 recent eruptions).
The Kizimen volcano on the western slope of the southern edge of the Tumrok mountain chain 265 km away from Petropavlovsk-Kamchatsky has become more active recently. Many strong earthquakes were registered in the region before October 2010, though we registered no meaningful changes in volcanic activity. However, we registered gas emissions from an old fuma-role (smoking crack, hole) on the northern slope 400 m away from the top. In October of 2010 three great earthquakes took place at a depth of 2 to 3 km. Satellite photos showed a thermal anomaly near Kizimen in December: hot matter was rising to the surface. Accordingly, data management experts of the Laboratory for Seismic and Volcanic Activity Research filed and sent the following forecast: "According to the available data, the volcano is becoming active: a powerful explosive eruption may occur next month and destroy the volcanic structure." Indeed, on December 12, 2010, seismic stations recorded a powerful explosive eruption of Kizimen. The eruption was confirmed by space monitoring data of the Alaska Volcano Observatory which registered an ash cloud about 10 km above moving northwest across the Kozyrevsk and Tigil settlements. Since then the volcano has been seismically active throwing up powerful lava flows, and gas-and-vapor. The violent eruption of 2011 changed greatly the surrounding landscape.
Air traffic controllers route the planes over Kamchatka away from active seismic zones. They are making use of our seismic monitoring data as well.
Опубликовано на Порталусе 24 ноября 2021 года
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