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1.
V. K. Lemzikov 《Journal of Volcanology and Seismology》2014,8(2):125-134
This study makes use of spectral models for tectonic earthquakes in application to volcano-tectonic (VT) and deep-focus long period volcanic (DL) earthquakes. For these earthquakes we adjusted the parameters of source spectra, and simultaneously, the medium where seismic waves propagate. We derived preliminary results to characterize the models of source spectra for volcanic earthquakes that occur on Klyuchevskoi Volcano. This method can also be used to estimate the attenuation parameters of seismic waves, which are important for the assessment of stress and strain in a volcanic medium. 相似文献
2.
V. M. Zobin 《Bulletin of Volcanology》1971,35(1):225-229
Determinations of the local mechanisms of three volcanic earthquakes are given connected with the eruption of the Sheveluch volcano (November, 1964). As initial material the data on first arrivals of P-waves are used. The local mechanism of all three earthquakes is close to a strike-slip type of faulting and similar to the focal mechanism of tectonic earthquakes of Kamchatka. One nodal surface of all the volcanic earthquakes strikes in the same direction as the outbursts of the directed volcano explosions. 相似文献
3.
Hetty Triastuty Masato Iguchi Takeshi Tameguri 《Journal of Volcanology and Geothermal Research》2009,187(1-2):1-12
Shallow volcano-tectonic (VT) earthquakes recorded at the Kuchinoerabujima island volcano in southwest Japan are analyzed in order to clarify the role of hydrothermal activity in the development of volcanic seismicity. From analysis of shallow VT earthquakes in 2006, two specific episodes of elevated seismicity are observed in April and November 2006. The VT earthquakes have hypocenters at depths of 0–0.4 km beneath the summit crater, and normal fault focal mechanisms with WNW–ESE extension consistent with the tensional stress field indicated by the alignment of craters and fissures. Although the hypocenters and focal mechanisms are found to be largely invariant during these episodes, the corner frequencies of the VT earthquakes underwent a pronounced increase and decrease accompanying the changes in seismicity rates. The corner frequencies increased to 20–25 Hz approximately one month prior to the onset of elevated seismicity, and then decreased to 10–15 Hz in the period of peak seismicity. The rupture length also decreased at the onset of seismicity, thereafter increasing as the seismicity continued. The peak seismicity in terms of the daily number of VT events was accompanied by inflation around the crater, suggestive of a pressure increase in the volcanic system. It is inferred that the increase in shallow VT seismicity and rupture length is related to the development of a fractured zone. The pressure increase in the volcanic system is attributed to the intrusion of hydrothermal fluids, which is supported by an observed increase in fumarolic temperature and activity. The preceding monochromatic events are thus considered to be generated by the effect of fluid-filled cracks. The shortening of rupture length is then inferred to be related to the closing of non-fluid-filled cracks in the fracture zone under the increasing pressure field, leading to a transition from monochromatic events to low-frequency and shallow VT seismicity. 相似文献
4.
5.
Albert Eggers Jeffery Krausse Harold Rush James Ward 《Journal of Volcanology and Geothermal Research》1976,1(3):229-236
Gravity changes of up to 1.2 ± 0.1 mgal (1 standard deviation) were measured at three points within 400 m of an active vent on Pacaya volcano, Guatemala during eleven days of January, 1975. For five continuous days gravity varied inversely with the average muzzle velocity of ejecta, the frequency of volcanic explosions, and the frequency of volcanic earthquakes. The gravity changes are most reasonably interpreted as the product of intravolcanic movements of magma with masses one to two orders of magnitude larger than any flow ever erupted from the volcano. However, elevation changes and/or combination of elevation and mass distribution changes could also have been an important factor in effecting the observed gravity variations. Because we lack elevation control on the gravity stations, we are unable to unequivocally conclude which factor or which combination of factors produced the gravity changes. The study indicates the possibility of gravity monitoring of hazardous volcanoes as a predictive tool, and as an added means for investigating the internal mechanism of volcanic eruptions. 相似文献
6.
长白山近代火山活动与地震 总被引:5,自引:0,他引:5
概述了长白山火山区的构造环境及其构造的活动性,以天池火山为主体的长白山火山区近代喷发的构造的活动,表现有继承与新生的构造双重性和不均衡的脉动性,区内的火山地震与区域性构造地震趋于同步活动。 相似文献
7.
长白山天池火山地震观测与应力状态的初步研究 总被引:5,自引:2,他引:3
1997年6~9月在长白山天池火山区布设了数字化流动地震观测台网,对长白山火山地震活动进行了近震源观测,获取了大量与火山活动相关的地震信息。通过本次观测及资料处理,对长白山火山地震及其所反映出的应力状态有了一定的认识,为长白山火山活动研究提供了科学依据。 相似文献
8.
A. V. Solomatin 《Journal of Volcanology and Seismology》2014,8(1):54-68
We used the data on the activity of volcanoes in Kamchatka and the North Kuril Islands for the period from 1840 to early 2013 to identify the most significant cyclic components. The resulting periodicities were compared with the recurrence spectrum for great (M ≥ 7.7) earthquakes in the Kuril-Kamchatka region for 1841–2012. We detected 52.8–54.0, 8.58, and 5.72-year cycles, which are common both to seismicity and to volcanic activity. The first interval is close to the three times the value of the 18.613-year lunar rhythm (55.84 years). The 8.58 and 5.72-year periodicities seem to be controlled by solar activity variations and are the second and third harmonics in the 17.15-year cycle. This cycle and its harmonics are used for long-term prediction of great (M ≥ 7.7) earthquakes in the Kuril-Kamchatka region as a whole. It was concluded that the existing increased hazard of great earthquake occurrence in the Kuril-Kamchatka region will last until February 2016 (a 40% probability of a great earthquake during that period). In addition, the long-period phase of increased seismic hazard will last until 2027 with the probability of great earthquakes being 1.6 times the long-term average value. 相似文献
9.
Characterization of the microseismic activity (M L <2.0) has been performed at Mt. Melbourne since 1990. We recorded a group of low frequency events with common morphological characteristics, i.e., an emerging onset, an unclear second phase and a sharply dropping coda. Spectral analysis of events recorded at more than one station indicates that the seismogram characteristics and spectral content are largely due to source effects. A polarization filter applied to a set of three component data revealed a first phase made up ofP waves followed (after about 0.9–1.4 sec.) by a second phase probably composed ofSH-type waves. Particle motion analysis detected a seismic ray angle direction mainly between N70°E and N110°E and apparent angle of incidence between 35° and 48° for the first phase. The studied seismicity was localized in an area on the eastern slope of Mt. Melbourne Volcano which presents a surface temperature anomaly (Mazzarini andSalvini, 1994). We formulate two hypotheses for the type of earthquakes recorded: 1) long-period events involving active presence of magmatic fluids in the source processes; 2) or the result of fracturing processes (shear?) in a medium characterized by transition between brittle and plastic behaviors. In the latter hypothesis the superficial thermal anomaly may be a symptom of this behavior at depth and is confirmed by the lown values observed for the exponential fit in the codaQ analysis. 相似文献
10.
Introduction ZHANG and ZHONG (1977), ZHANG, et al (1978) and ZHANG (1984) pointed out that Chinese mainland is divided into two parts by the NS-trending tectonic belt, i.e., the eastern area and the western area, and each area is divided into tectonic blocks by faults. In the eastern area, the faults are trending NNE and NNW, mainly NNE, and the long axis strike of blocks is nearly trending NS. In the western area, faults are trending NEE and NWW, mainly NWW, long axis strike … 相似文献
11.
讨论了有关五大连池火山的构造背景,区域构造特征,历史和现代火山活动以及火山灾害及其预报和防治等等。 相似文献
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P. W. Lipman 《Bulletin of Volcanology》1980,43(4):703-725
Flow by flow mapping of the 65-km-long anbaerial part of the southwest rift zone and adjacent flanks of Mauna Loa Volcano, Hawaii, and about 50 new14C dates on charcoal from beneath these flows permit estimates of rates of lava accumulation and volcanic growth over the past 10,000 years. The sequence of historic eraptions along the southwest rift zone, beginning in 1868, shows a general pattern of uprift migration and increasing eruptive volume, culminating in the great 1950 eruption. No event comparable to 1950, in terms of volume or vent length, is evident for at least the previous 1,000 years. Rates of lava accumulation during the historic period were several times higher than the average rate for the preceding few thousand years along the southwest rift zone and adjacent flanks. Rates of lava accumulation along the zone have been subequal to those of Kilauea Volcano during the historic period but they were much lower in late prehistoric time (anpubl. Kilauea data byR.T. Holcomb). Thus, only about 30% of the surface of the southwest side of Mauna Loa has been covered by lava during the last 1,000 years, as contrasted with about 90% of the subaerial surface of Kilauea. Rates of surface covering and volcanic growth have been markedly asymmetric along Mauna Loa’s southwest rift zone. Accumulation rates have been about half again as great on the northwest side of the rift zone in comparison with the southeast side. The difference apparently reflects a westward lateral shift of the rift zone of Mauna Loa away from Kilauea Volcano, which may have acted as a barrier to symmetrical growth of the rift zone. 相似文献
14.
Hemendra Acharya 《Pure and Applied Geophysics》1987,125(6):1097-1118
Spatial relationship between volcanism and seismicity prior to the occurrence of several great interplate earthquakes in the circum Pacific area has been examined in order to understand the process of underthrusting in detail. The locations of the epicenters of the great earthquakes have been examined in terms of locations of concentrated volcanic and seismic activity in a short time period in order to determine if there is any relationship between these activities, and whether such relationships can be used to refine the underthrusting model. The study shows that in most cases, (1) there is no volcanic activity in the vicinity of the epicenter of the great earthquake and (2) maximum volcanic activity is localized, i.e., volcanoes adjacent to one another exhibit considerable activity in a short time period. Very little systematic spatial relationship between these three parameters is observed although in most cases, there is no volcanic activity at the time of maximum earthquake activity. Locations of active volcanoes and earthquake activity, during the five years prior to the occurrence of the great earthquake, do not appear to be a guide to the epicenter of the great earthquake. This study therefore suggests that although there is temporal relationship between the occurrence of maximum volcanic and seismic activity and the occurrence of great earthquake, there appears to be no systematic spatial relationship between these three parameters. 相似文献
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16.
V. M. Zobin 《Bulletin of Volcanology》1972,36(4):561-571
The focal mechanism solutions for Type A volcanic earthquakes connected with eruptions of the Miake-sima, Tori-shima (Japan) and Beerenberg (Jan Mayen Island) volcanoes are presented. All the considered volcanic earthquakes show focal mechanism of the strike-slip type of faulting. Stresses acting in the volcanic earthquake foci can well be attributed to the regional stress systems. 相似文献
17.
长白山天池火山地震观测以来,记到了许多微小地震,对此,引起了许多专家们的关注。本文通过几年来观测到的资料分类和比较研究,对长白山天池火山地震波形特征进行详细的剖析,把长白山地震波形分成两大类,从第一类波形中找出反射波特征。 相似文献
18.
Large thrust earthquakes and volcanic eruptions 总被引:2,自引:0,他引:2
Sergio E. Barrientos 《Pure and Applied Geophysics》1994,142(1):225-237
Forty-eight hours after the occurrence of the May 22, 1960 (M
W
=9.5) Chile earthquake, Puyehue volcano initiated its eruptive activity. The closeness in space and time of both phenomena provides us with a unique opportunity to examine the possible causal relationship between the sudden strain change and the mechanism of the eruption. From the slip distribution of the 1960 event (Barrientos andWard, 1990) and a static propagator technique, which allows for variable slip faults in vertically heterogeneous media, I calculate the strain field and its depth dependence in the region beneath the volcano. The presented semi-analytical formalism can be applied to any two-dimensional dipping fault. Calculations show extension at the surface of the order of 40 strain, in agreement with what was observed in triangulation networks in the central valley about 50 km oceanward from the line of volcanoes. The amplitude of the strain field beneath the volcano is uniform up to a depth of 20 km and decreases downward. The sudden extension of the region is thought to be the main factor in facilitating the eruption of the volcano. It is postulated that strain beneath the volcano triggered the eruption of the Puyehue-Cordón Caulle volcanic system because it was in a mature stage of its eruptive cycle and there was lack of eruptive activity in other volcanoes located along the 1960 rupture region in the immediate period following the earthquake. 相似文献
19.
Alain Demant Patrick Lestrade Ruananza T Lubala Ali B Kampunzu Jacques Durieux 《Bulletin of Volcanology》1994,56(1):47-61
Three major phases are distinguished during the growth of Nyiragongo, an active volcano at the western limit of the Virunga
Range, Zaire. Lavas erupted during phase 1 are strongly undersaturated melilitites characterized by the presence of kalsilite
phenocrysts, perovskite, and the abundance of calcite in the matrix. Such lavas crop out mainly on the inner crater wall and
progressively evolve toward more aphyric melilite nephelinites well represented on the flanks of the volcano. Adventive vents
lying at the base of the cone developed along radial fracture systems and erupted olivine and/or clinopyroxene – rich melilitites
or nephelinites. Stage 2 lavas are melilite-free nephelinites. Clinopyroxene is the main phenocryst and feldspathoids are
abundant in the lavas exposed on the crater wall. These flows result from periodic overflowing of a magma column from an open
crater. Extensive fissure flows which erupted from the base of the cone at the end of this stage are related to widespread
draining out of magma which in turn induces the formation of the summit pit crater. Magmas erupted during stage 3 are relatively
aphyric melilite nephelinites and the main volcanological characteristic is the permanent lava lake observed into the pit
crater until the 1977 eruption. Fluctuations of the level of the lava lake was responsible for the development of the inner
terraces. Periodic overflowing of the lava lake from the central pit formed the nepheline aggregate lava flows. Petrography
and major element geochemistry allow the determination of the principal petrogenetic processes. Melilitites and nephelinites
erupted from the summit crater are lavas derived, via clinopyroxene fractionation, from a more primitive melt. The abundance
of feldspathoids in these lavas is in keeping with nepheline flotation. Aphyric melilite nephelinites covering the flanks
and the extensive fissure flows have a homogeneous chemical composition; rocks from the historical lava lake are slightly
more evolved. All these lavas differentiated in a shallow reservoir. Lavas erupted from the parasitic vents are mainly olivine
and/or clinopyroxene-phyric rocks. Rushayite and picrites from Muja cone are peculiar high-magnesium lavas resulting from
the addition of olivine xenocrysts to melilitic or nephelinitic melts. Fluid and melt inclusions in olivine and clinopyroxene
phenocrysts indicate a crystallization depth of 10–14 km. A model involving two reservoirs located at different depths and
periodically connected is proposed to explain the petrography of the lavas; this hypothesis is in accordance with geophysical
data.
Received: July 8, 1993/Accepted: September 10, 1993 相似文献