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1.
2.
We considered the seismic regime in the upper 70–100 km of the lithosphere and identified the layers (at depths of about 10,
20–30, and 60–80 km) characterized by relatively reduced effective strength and increased seismicity. The existence of such
layers is related to changes in the regime of fluid-rock interaction, namely, to the characteristic depths of a jump-like
decrease in the effective permeability of rocks and an increase in the spatial homogeneity of a fluid-rock system. 相似文献
3.
L. I. Gontovaya S. V. Popruzhenko I. V. Nizkous 《Journal of Volcanology and Seismology》2010,4(4):232-247
We consider results from modeling the crustal and upper mantle velocity structure in Kamchatka by seismic tomography and compare
these with gravity data and present-day tectonics. We found a well-pronounced (in the physical fields) vertical and lateral
variation for the upper mantle and found that it is controlled by fault tectonics. Not only are individual lithosphere blocks
moving along faults, but also parts of the Benioff zone. The East Kamchatka volcanic belt (EKVB) is confined to the asthenospheric
layer (the asthenosphere lens) at a depth of 70–80 km; this lens is 10–20 km thick and seismic velocity in it is lower by
2–4%. The top of the asthenosphere lens has the shape of a dome uplift beneath the Klyuchevskoi group of volcanoes and its
thickness is appreciably greater; overall, the upper mantle in this region is appreciably stratified. A low-velocity heterogeneity
(asthenolith) at least 100 km thick has been identified beneath the Central Kamchatka depression; we have determined its extent
in the upper mantle and how it is related to the EKVB heterogeneities. Gravity data suggest the development of a rift structure
under the Sredinnyi Range volcanic belt. The Benioff zone was found to exhibit velocity inhomogeneity; the anomalous zones
that have been identified within it are related to asthenosphere inhomogeneities in the continental and oceanic blocks of
the mantle. 相似文献
4.
V. P. Sivokon’ 《Geomagnetism and Aeronomy》2011,51(4):513-519
The paper proposes a method for observing electromagnetic fluctuations in a range of geomagnetic pulsations based on the registration
of electrojet variations in the ULF-VLF hiss band modulated by these electromagnetic fluctuations. The observations of natural
noise at the Kamchatka electric networks made it possible to detect electromagnetic fluctuations in the (35–67) × 10−3 Hz frequency band. It has been indicated that these fluctuations can originate in the ionospheric-magnetospheric oscillatory
circuit formed by magnetic force tubes (inductance) and the electrojet-Earth region (capacity). 相似文献
5.
M. I. Beloglazov V. M. Demkin A. A. Krasilnikov L. M. Kukin Yu. Yu. Kulikov V. G. Ryskin V. N. Shanin 《Geomagnetism and Aeronomy》2010,50(2):256-262
As a result of the long-term observations lead in region of Kola Peninsula, connection between character of variations of
the ozone content in a stratosphere of Arctic regions and behavior and structure of a winter polar vortex is established.
During winter seasons with well developed cyclone and duration of stable existence not less than 1.5–2 months were observed
extremely low ozone number density at heights 20–25 km connected, apparently, with its chemical destruction. On the other
hand, during disturbances of the vortex, accompanied strong stratospheric warming, was registered almost double increase of
ozone amount in a high-altitude interval from 20 up to 40 km. Comparison of results of ground-based microwave monitoring of
an ozone layer to data of the satellite instrument EOS MLS installed on satellite AURA is lead. In most cases comparison has
shown satisfactory within the limits of an error of measurements coincidence of results. However in conditions of atmospheric
disturbances when arose significant spatial heterogeneity, the discrepancy of results of comparison was marked. The possible
reasons which cause the detected disagreement in results are discussed. 相似文献
6.
B. M. Shevtsov V. V. Bychkov V. N. Marichev A. S. Perezhogin A. V. Shumeiko 《Geomagnetism and Aeronomy》2009,49(8):1302-1304
The dynamics of aerosol layers in comparison with geomagnetic and ionospheric data has been studied based on the nighttime
single-frequency lidar sounding of the atmosphere over Kamchatka at altitudes of 10 to 90 km. The relation of the aerosol
density to solar, magnetic, and ionospheric activity has been studied, and the stratospheric aerosol formation mechanisms
have been considered. It has been indicated that variations in the aerosol density correlate with radiowave absorption, perturbations
of the ionospheric parameters, and geomagnetic characteristics. The spatial and time scales of aerosol layers have been estimated.
The role of stratospheric aerosol as an indicator of geophysical processes is discussed. 相似文献
7.
The caldera-forming eruption of Volcán Ceboruco, Mexico 总被引：1，自引：1，他引：0
3 of magma erupted, ∼95% of which was deposited as fall layers. During most of the deposition of P1, eruptive intensity (mass
flux) was almost constant at 4–8×107 kg s−1, producing a Plinian column 25–30 km in height. Size grading at the top of P1 indicates, however, that mass flux waned dramatically,
and possibly that there was a brief pause in the eruption. During the post-P1 phase of the eruption, a much smaller volume
of magma erupted, although mass flux varied by more than an order of magnitude. We suggest that caldera collapse began at
the end of the P1 phase of the eruption, because along with the large differences in mass flux behavior between P1 and post-P1
layers, there were also dramatic changes in lithic content (P1 contains ∼8% lithics; post-P1 layers contain 30–60%) and magma
composition (P1 is 98% rhyodacite; post-P1 layers are 60–90% rhyodacite). However, the total volume of magma erupted during
the Jala pumice event is close to that estimated for the caldera. These observations appear to conflict with models which
envision that, after an eruption is initiated by overpressure in the magma chamber, caldera collapse begins when the reservoir
becomes underpressurized as a result of the removal of magma. The conflict arises because firstly, the P1 layer makes up too
large a proportion (∼75%) of the total volume erupted to correspond to an overpressurized phase, and secondly, the caldera
volume exceeds the post-P1 volume of magma by at least a factor of three. The mismatches between model and observations could
be reconciled if collapse began near the beginning of the eruption, but no record of such early collapse is evident in the
tephra sequence. The apparent inability to place the Jala pumice eruptive sequence into existing models of caldera collapse,
which were constructed to explain the formation of calderas much greater in volume than that at Ceboruco, may indicate that
differences in caldera mechanics exist that depend on size or that a more general model for caldera formation is needed.
Received: 18 November 1998 / Accepted: 23 October 1999 相似文献
8.
G. I. Druzhin V. N. Uvarov V. A. Mullayarov V. I. Kozlov A. A. Korsakov 《Geomagnetism and Aeronomy》2010,50(2):211-218
The effect of the solar eclipse that occurred on August 1, 2008, on the level of the natural electro-magnetic emission signals
in the ELF-VLF range, simultaneously observed at Kamchatka and in Yakutsk, and the variations in the amplitude and phase of
signals from the VLF radiostations, registered in Yakutsk, has been considered. The VLF radiostations in Krasnodar, Novosibirsk,
and Khabarovsk successively emitted signals at frequencies of 11 905, 12 649, and 14 880 Hz. Based on the observations of
the signals from these radiostations, it has been established that the signal amplitudes and phases increased by 3–5% and
30°–45° when the signals crossed the lunar shadow region. The synchronous registration of the ELF-VLF noise emission indicated
that a bay-like increase and the following decrease in the emission to the background level was observed at both receiving
points during the eclipse from ∼1000 to 1130 UT. This effect was registered at frequencies of 0.6–5.6 kHz in Yakutsk and at
lower (30–200 Hz) and higher (2.5–11 kHz) frequencies at Kamchatka. In this case the noise emission intensity maximum was
observed when the lunar shadow maximally approached the registration point. At higher frequencies, the emission maximum was
observed simultaneously at both points (at 1100 UT) but with a delay relative to the maximum at lower frequencies. The possible
causes of the appearance of the solar eclipse effects in the natural ELF-VLF emission are considered. 相似文献
9.
S. I. Boldyrev G. S. Ivanov-Kholodny O. P. Kolomiitsev A. I. Osin 《Geomagnetism and Aeronomy》2011,51(4):546-549
This article studies long-period variations in the Earth’s upper atmosphere density over several solar activity cycles, using
long-term data on the evolution of motion of three artificial satellites (Intercosmos-19, Meteor-1-2, and Cosmos-1154) in
orbits at heights of 400–1000 km. The time interval when the satellites were in the orbits covered three solar activity cycles
(partly the 21st, completely the 22nd, and partly the 23rd). It is found that the variations in the average density of the
upper atmosphere at heights of 400–600 km in the 1980–2000 period were governed by the changes in the solar activity level. 相似文献
10.
Based on observations of mesopause emissions, namely, emissions of hydroxyl (band (6-2)) and molecular oxygen (band (0-1)
of the atmospheric system), their systematic nighttime and seasonal variations are determined at Zvenigorod Observatory in
2000–2008. It is shown that the intensity of hydroxyl emission decreases during the entire night or first half-night, probably
due to the influence of the chemical sink of atomic oxygen on the nighttime behavior of hydroxyl emission. The nighttime behavior
of the intensity of molecular oxygen emission is explained by the action of atmospheric tides. The seasonal behavior of emissions
is characterized by two minima, in April–May and December; it is caused by the annual behavior of the atomic oxygen content,
temperature, and atmospheric density in the emitting layer. Based on the emission data, we determined the seasonal variations
of atomic oxygen at heights of ∼87 km (maximum of hydroxyl emission) and ∼95 km (maximum of molecular oxygen emission). 相似文献
11.
We measured and interpreted 30 physical magnetotelluric sounding sites using an SGS-E station and 20 km of electrical profiling
observations using SDVR-4M instrumentation. We constructed a map of seismicity, an interpretation map, and four geoelectric
sections, which give an idea of the deep structure for the Kulu earthquake-generating zone. A general geoelectric upper crustal
model was developed for the zone down to depths of 20–22 km. Three nearly vertical conductive volumes were identified (thickness
3–5 km, depth 10–22 km), which provide the positions of seismically active deep-seated faults that pinpoint the Kulu earthquake-generating
zone. The preliminary boundary of the zone was determined. It was found that earth-quake epicenters are confined to lithosphere
volumes with increased concentrations of conductive layers and zones. 相似文献
12.
G. N. Kopylova G. M. Steblov S. V. Boldina I. A. Sdel’nikova 《Izvestiya Physics of the Solid Earth》2010,46(1):47-56
A method for point estimation of coseismic volume deformation from amplitudes of earthquake-induced jumps in the water level
and from the tidal sensitivity of the water level is presented. Application of this method is illustrated by six Kamchatka
earthquakes of 1997–2004 with M
w
= 6.2–7.8 that occurred 128–316 km from the YuZ-5 well. Estimates of coseismic deformation provided by the level gage observations
and by the model agree in amplitude and sign. The model reproduces an extended dislocation source in a homogeneous elastic
isotropic half-space. Source rupture parameters correspond to focal mechanisms from the CMT international catalog. Consistence
in experimental and theoretical estimates of the volume coseismic deformation indicates the high strain-resistance properties
of YuZ-5 borehole and the possibility of quantitative estimation of seismotectonic deformation from high-precision water level
measurements with time resolution not lower than 10 minutes. 相似文献
13.
Lightning and electrification at volcanoes are important because they represent a hazard in their own right, they are a component
of the global electrical circuit, and because they contribute to ash particle aggregation and modification within ash plumes.
The role of water substance (water in all forms) in particular has not been well studied. Here data are presented from a comprehensive
global database of volcanic lightning. Lightning has been documented at 80 volcanoes in association with 212 eruptions. The
Volcanic Explosivity Index (VEI) could be determined for 177 eruptions. Eight percent of VEI = 3–5 eruptions have reported
lightning, and 10% of VEI = 6, but less than 2% of those with VEI = 1–2. These findings suggest consistent reporting for larger
eruptions but either less lightning or possible under-reporting for small eruptions. Ash plume heights (142 observations)
show a bimodal distribution with main peaks at 7–12 km and 1–4 km. The former are similar to heights of typical thunderstorms
and suggest involvement of water substance, whereas the latter suggest other factors contributing to electrical behavior closer
to the vent. Reporting of lightning is more common at night (56%) and less common in daylight (44%). Reporting also varied
substantially from year to year, suggesting that a more systematic observational strategy is needed. Several weak trends in
lightning occurrence based on magma composition were found. The bimodal ash plume heights are obvious only for andesite to
dacite; basalt and basaltic-andesite evenly span the range of heights; and rhyolites are poorly represented. The distributions
of the latitudes of volcanoes with lightning and eruptions with lightning roughly mimic the distribution of all volcanoes,
which is generally flat with latitude. Meteorological lightning, on the other hand, is common in the tropics and decreases
markedly with increasing latitude as the ability of the atmosphere to hold water decreases poleward. This finding supports
the idea that if lightning in large (deep) eruptions depends on water substance, then the origin of the water is primarily
magma and not entrainment from the surrounding atmosphere. Seasonal effects show that more eruptions with lightning were reported
in winter (bounded by the respective autumnal and vernal equinoxes) than in summer. This result also runs counter to the expectations
based on entrainment of local water vapor. 相似文献
14.
K.V.S. Badarinath Shailesh Kumar Kharol Anu Rani Sharma 《Journal of Atmospheric and Solar》2009,71(1):112-120
Agriculture crop residue burning in tropics is an important source of atmospheric aerosols and monitoring their long-range transport is an important element in climate change studies. Synchronous measurements using micro-pulsed lidar, MICROTOPS-II sun photometer, multi-filter rotating shadow band radiometer (MFRSR) on aerosol optical depth and ground reaching solar irradiance were carried at an urban location in central region of India. Aerosol backscatter profiles obtained from micro-pulse lidar showed elevated aerosol layers up to ～3 km on certain days during October 2007. Satellite data observations on aerosol properties suggested transport of particles from agriculture crop residue burning in Indo-Gangetic Plains over large regions. Radiative forcing of aerosols estimated from SBDART model with input information on aerosol chemical properties, aerosol optical depth and single scattering albedo and broadband solar irradiance measurements using MFRSR showed good correlation (R=0.98). 相似文献
15.
Volcanic plumes and wind: Jetstream interaction examples and implications for air traffic 总被引：1，自引：1，他引：0
M.I. Bursik S.E. Kobs A. Burns O.A. Braitseva L.I. Bazanova I.V. Melekestsev A. Kurbatov D.C. Pieri 《Journal of Volcanology and Geothermal Research》2009,186(1-2):60
Volcanic plumes interact with the wind at all scales. On smaller scales, wind affects local eddy structure; on larger scales, wind shapes the entire plume trajectory. The polar jets or jetstreams are regions of high [generally eastbound] winds that span the globe from 30 to 60° in latitude, centered at an altitude of about 10 km. They can be hundreds of kilometers wide, but as little as 1 km in thickness. Core windspeeds are up to 130 m/s. Modern transcontinental and transoceanic air routes are configured to take advantage of the jetstream. Eastbound commercial jets can save both time and fuel by flying within it; westbound aircraft generally seek to avoid it.Using both an integral model of plume motion that is formulated within a plume-centered coordinate system (BENT) as well as the Active Tracer High-resolution Atmospheric Model (ATHAM), we have calculated plume trajectories and rise heights under different wind conditions. Model plume trajectories compare well with the observed plume trajectory of the Sept 30/Oct 1, 1994, eruption of Kliuchevskoi Volcano, Kamchatka, Russia, for which measured maximum windspeed was 30–40 m/s at about 12 km. Tephra fall patterns for some prehistoric eruptions of Avachinsky Volcano, Kamchatka, and Inyo Craters, CA, USA, are anomalously elongated and inconsistent with simple models of tephra dispersal in a constant windfield. The Avachinsky deposit is modeled well by BENT using a windspeed that varies with height.Two potentially useful conclusions can be made about air routes and volcanic eruption plumes under jetstream conditions. The first is that by taking advantage of the jetstream, aircraft are flying within an airspace that is also preferentially occupied by volcanic eruption clouds and particles. The second is that, because eruptions with highly variable mass eruption rate pump volcanic particles into the jetstream under these conditions, it is difficult to constrain the tephra grain size distribution and mass loading present within a downwind volcanic plume or cloud that has interacted with the jetstream. Furthermore, anomalously large particles and high mass loadings could be present within the cloud, if it was in fact formed by an eruption with a high mass eruption rate. In terms of interpretation of tephra dispersal patterns, the results suggest that extremely elongated isopach or isopleth patterns may often be the result of eruption into the jetstream, and that estimation of the mass eruption rate from these elongated patterns should be considered cautiously. 相似文献
16.
Results are reported from a detailed study of central Kamchatka seismicity for the period 1962–1997 based on a modification
of the traditional approach. The approach involves (a) a detailed structure of the seismic region that recognizes the Kronotskii
and Shipunskii geoblocks and two further blocks, the continental slope, and the offshore portion, (b) a study of variations
in the rate of M = 3.0–7.2 earthquakes and the amount of seismic energy released at depths of 0–50 and 51–100 km, (c) a study
of seismicity variability, and (d) separate estimates of the recurrence of crust-mantle earthquakes (depths 0–50 km) and mantle
events (51–100 km). As a result, apart from corroborating the fact of a quiescence preceding the December 5, 1997 Kronotskii
earthquake (M 7.9), we also found that a relationship exists between its beginning and the position of the earthquake-generating
region relative to the mainshock epicenter. The quiescence dominates the seismic process during the pre-mainshock period and
is characterized by a decreased rate of earthquakes (the first feature) and a decreased amount of seismic energy release (the
second feature). Based on the first feature, we found that the quiescence started in 1987 throughout the entire depth range
(0–100 km) in both parts of the Kronotskii geoblock close to the rupture zone of the eponymous earthquake. As to the Shipunskii
geoblock, which is farther from the rupture zone, the quiescence began in the mantle of the inner area first (1988) and somewhat
later at depths of 0–50 km within the continental slope (1989). By the second feature, the quiescence began at shallower depths
in the inner area of the Kronotskii geoblock at the same time and later on (a year later) in the mantle (1988). Under the
continental slope of the trench in the Shipunskii geoblock the shallower quiescence also began in 1987, while it was 3 years
late in the inner zone (1990) and involved the earthquake-generating earth volume at depths of 0–100 km. These data are identical
with or sufficiently close to the estimate for the beginning of this quiescence using a circular area of radius 150 km that
combines the Kronotskii and Shipunskii geoblocks by the RTL method (1990). 相似文献
17.
Fabrizio Alfano Costanza Bonadonna Alain C. M. Volentik Charles B. Connor Sebastian F. L. Watt David M. Pyle Laura J. Connor 《Bulletin of Volcanology》2011,73(5):613-630
On May 1st 2008 Mount Chaitén (southern Chile) interrupted a long period of quiescence, generating a sequence of explosive
eruptions and causing the evacuation of Chaitén town located a few kilometers south of the volcano. The activity was characterized
by several explosive events each associated with plumes which reached up to about 19 km above sea level. The products were
dispersed across a wide area, with the finest ash reaching the Atlantic coast of Argentina. Our field observations in the
proximal-medial area (3–25 km from the vent) indicate that the May 2008 tephra deposit consists of numerous layers, most of
which can be correlated with individual eruptive events. These layers vary from extremely fine-grained ash to layers of lapilli
and blocks, composed of both juvenile and lithic material. Here we describe the stratigraphy and physical characteristics
of the May 2008 deposits, and propose a reconstruction of the timing of the May 2008 events. The deposits are mainly associated
with the three main explosive phases which occurred on 1st–2nd May, 3rd–5th May and 6th May, with an estimated bulk tephra
volume of 0.5–1.0 km3 (integration of both exponential and power-law fitting). For the 6th May event, represented by a layer composed mainly of
lithic lapilli and blocks (>2 mm), an isopleth map was compiled from which a 19 km plume height was determined, which is in
good agreement with satellite observations. 相似文献
18.
I. N. Tikhonov 《Journal of Volcanology and Seismology》2010,4(3):213-221
We report the results from a search for statistically significant (at a significance level of <0.05) periodicities that synchronize
the occurrence of large shallow (h ≤ 100 km) earthquakes in the eight world regions with the highest level of seismicity. The periodicities in question include
the synodic periods of planets of the solar system (Mercury, Venus, Mars, and Jupiter), as well as the precession period of
the lunar orbit. In five of the eight regions we have found statistically significant results for the period T ≈ 780 days, corresponding to the synodic period of Mars. The lunar cycle and the period of Mercury were significant in two
regions. These results cannot be accounted for by invoking the disturbing influence of gravitational and tidal forces due
to planets other than the Earth. The significant periodicities were used to develop a forecast (for the period 2004–2009)
of the most probable time intervals for the occurrence of large earthquakes in four regions: Kamchatka, the South Kurils,
northeastern Japan, and the Nankai trough. 相似文献
19.
We report results from a detailed study of seismicity in central Kamchatka for the period from 1960 to 1997 using a modified
traditional approach. The basic elements of this approach include (a) segmentation of the seismic region concerned (the Kronotskii
and Shipunskii geoblocks, the continental slope and offshore blocks), (b) studying the variation in the rate of M = 4.5–7.0 earthquakes and in the amount of seismic energy release over time, (c) studying the seismicity variations, (d)
separate estimates of earthquake recurrence for depths of 0–50 and 50–100 km. As a result, besides corroborating the fact
that a quiescence occurred before the December 5, 1997, M = 7.9 Kronotskii earthquake, we also found a relationship between the start of the quiescence and the position of the seismic
zone with respect to the rupture initiation. The earliest date of the quiescence (decreasing seismicity rate and seismic energy
release) was due to the M = 4.5–7.0 earthquakes at depths of 0–100 km in the Kronotskii geoblock (8–9 years prior to the earthquake). The intermediate
start of the quiescence was due to distant seismic zones of the Shipunskii geoblock and the circular zone using the RTL method, combining the Shipunskii and Kronotskii geoblocks (6 years). Based on the low magnitude seismicity (M≥2.6) at depths of 0–70 km in the southwestern part of the epicentral zone (50–100 km from the mainshock epicenter), the quiescence
was inferred to have occurred a little over 3 years (40 months) before the mainshock time and a little over 2 years (25 months)
in the immediate vicinity of the epicenter (0–50 km). These results enable a more reliable identification of other types of
geophysical precursors during seismic quiescences before disastrous earthquakes. 相似文献
20.
Data from the literature were used to systematize intermediate-term (with advance times of 1 month to ∼2.5 years) precursors
to the M ≥ 6.6 Kamchatka earthquakes of 1987–2004. The precursors were observed as changes in seismological, geodetic, geophysical,
water-level, and hydrochemical parameters. Retrospective assessment of the information content in these intermediate-term
precursors for earthquake prediction is in progress. The focus was on estimating the occurrence times of various precursors
as functions of earthquake parameters (magnitude M, hypocentral distance R, and epicenter location). In the conditions of the Kamchatka observing network, precursors can be identified by a combination
of methods, mostly before M ∼ 7 earthquakes or greater south of the Kronotskii Peninsula, for which M/logR ≥ 3. It is shown that the relative proportion of earthquakes for which precursors have been identified in the observations
considered here is 0.43–0.86. 相似文献