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1.
Wang Yanzhao 《中国地震研究》2007,21(4):355-364
Seismological and geodetic observations indicate that slow slip sometimes occurs in active fault zones beneath the seismogenic depth, and large slow slip can result in transient ground motion. Slow earthquakes, on the other hand, emit tremor-like signals within a narrow frequency band, and usually produce no catastrophic consequences. In general, slow slip and slow earthquakes probably correspond to deformation processes associated with releasing elastic energy in fault zones, and understanding their mechanisms may help improve our understanding of fault zone dynamic processes. This article reviews the research progress on slow slip and slow earthquakes over the last decade. Crustal motion and tremor activities associated with slow slip and slow earthquakes have been investigated extensively, mainly involving locating sources of slow slip and slow earthquakes and numerical modeling of their processes. In the meantime, debates have continued about slow slip and slow earthquakes, such as their origins, relationship, and mechanisms. 相似文献
2.
Ismail Albayrak Vladimir Nikora Oliver Miler Matthew T. O’Hare 《Aquatic Sciences - Research Across Boundaries》2014,76(2):269-294
Flow–plant interactions are experimentally investigated at leaf, stem, and shoot scales in an open-channel flume at a range of Reynolds numbers. The experiments included measurements of instantaneous drag forces acting on leaves, stems, and shoots of the common freshwater plant species Glyceria fluitans, complemented with velocity measurements, high-resolution video recordings, and biomechanical tests of leaf and stem properties. The analyses of bulk statistics, power spectral densities, transfer functions, and cross-correlations of measured velocities and drag forces revealed that flow characteristics, drag force, and plant biomechanical and morphological properties are strongly interconnected and scale-dependent. The plant element–flow interactions can be subdivided into two classes: (I) passive interactions when the drag variability is due to the time variability of the wetted and frontal areas and squared approach velocity (due to the large-scale turbulence); and (II) active interactions representing a range of element-specific instabilities that depend on the element flexural rigidity and morphology. Implications of experimental findings for plant biophysics and ecology are briefly discussed. 相似文献
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IntroductionAccordingtoEarthquakeResistanceandDisasterReductionLawforthePeoplesRepublicofChina,twomethodsareadoptedforseismicdesignoftheconstructionprojectsinChina.Forkeyprojectsandtheprojectseasytocauseserioussecondarydisasters,seismicsafetyevaluationsmustbecarriedout.Andbasedontheresults,seismicfortificationstandardsaredeterminedtomakeseismicdesign.Forgeneralindustrialandcivilbuildings,seismicdesignsarecarriedoutaccordingtotheseismicfortificationstandardsstipulatedbyseismiczonationmap(Ch… 相似文献
5.
Luo Wei Luo Zhuoli and Chen ShangpingNational Center for Seismic Data Informanon SSB Beijing China Center for Analysis Prediction SSB Beijing China 《中国地震研究》1996,(3)
In this work,the vertical deformation,horizontal displacement,and stress fields of arcuate tectonics are theoretically derived from the horizontal tectonic stress; then the characteristics of tectonic movement,seismicity,and focal mechanism of arcuate tectonics of the entire world are explained.It is pointed out that the island arc and other arcuate tectonics are gradually developed under the displacement and stress fields of the arcuate tectonics and that the under-thrusting action of the ocean plate is secondary.The distance formulas between the volcanic arc and the trench are suggested and also that theoretical results are consistent with actual data. 相似文献
6.
Jacob B. Lowenstern Heather Bleick Jorge A. Vazquez Jonathan M. Castro Peter B. Larson 《Bulletin of Volcanology》2012,74(10):2303-2319
We investigated the distribution of Cl, F, Li, and Be in pumices, obsidians, and crystallized dome rocks at Chaitén volcano in 2008?C2009 in order to explore the behavior of these elements during explosive and effusive volcanic activity. Electron and ion microprobe analyses of matrix and inclusion glasses from pumice, obsidian, and microlite-rich dome rock indicate that Cl and other elements were lost primarily during crystallization of the rhyolitic dome after it had approached the surface. Glass in pumice and microlite-free obsidian has 888?±?121?ppm Cl, whereas residual glass in evolved microlite-rich dome rock generally retains less Cl (as low as <100?ppm). Estimated Cl losses were likely >0.7?Mt Cl, with a potential maximum of 1.8?Mt for the entire 0.8-km3 dome. Elemental variations reflect an integrated bulk distribution ratio for Cl?>?1.7 (1.7 times more Cl was degassed or incorporated into crystals than remained in the melt). Because Cl is lost dominantly as the very last H2O is degassed, and Cl is minimally (if at all) partitioned into microlites, the integrated vapor/melt distribution ratio for Cl exceeds 200 (200 times more Cl in the evolved vapor than in the melt). Cl is likely lost as HCl, which is readily partitioned into magmatic vapor at low pressure. Cl loss is accelerated by the change in the composition of the residual melt due to microlite growth. Cl loss also may be affected by open-system gas fluxing. Integrated vapor-melt distribution ratios for Li, F, and Be all exceed 1,000. On degassing, an unknown fraction of these volatiles could be immediately dissolved in rainwater. 相似文献
7.
Biogeomorphology has been expanding as a discipline, due to increased recognition of the role that biology can play in geomorphic processes, as well as due to our increasing capacity to measure and quantify feedback between biological and geomorphological systems. Here, we provide an overview of the growth and status of biogeomorphology. This overview also provides the context for introducing this special issue on biogeomorphology, and specifically examines the thematic domains of biogeomorphological research, methods used, open questions and conundrums, problems encountered, future research directions, and practical applications in management and policy (e.g. nature-based solutions). We find that whilst biogeomorphological studies have a long history, there remain many new and surprising biogeomorphic processes and feedbacks that are only now being identified and quantified. Based on the current state of knowledge, we suggest that linking ecological and geomorphic processes across different spatio-temporal scales emerges as the main research challenge in biogeomorphology, as well as the translation of biogeomorphic knowledge into management approaches to environmental systems. We recommend that future biogeomorphic studies should help to contextualize environmental feedbacks by including the spatio-temporal scales relevant to the organism(s) under investigation, using knowledge of their ecology and size (or metabolic rate). Furthermore, in order to sufficiently understand the ‘engineering’ capacity of organisms, we recommend studying at least the time period bounded by two disturbance events, and recommend to also investigate the geomorphic work done during disturbance events, in order to put estimates of engineering capacity of biota into a wider perspective. Finally, the future seems bright, as increasingly inter-disciplinary and longer-term monitoring are coming to fruition, and we can expect important advances in process understanding across scales and better-informed modelling efforts. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献
8.
Temporal and spatial variation and stability of the oasis in the Sangong River Watershed, Xinjiang, China 总被引：5，自引：0，他引：5
The unique ecological landscapes are composed of the mountain systems with the obviousvertical differentiation, vast natural desert systems, and oasis systems on which the human beings rely for the existence in the arid areas in West China. Oases are the … 相似文献
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Olga Sarychikhina Ewa Glowacka Braulio Robles F. Alejandro Nava Miguel Guzmán 《Pure and Applied Geophysics》2015,172(11):3139-3162
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《中国地震研究》1994,(1)
Mantle convection results in plate movement.Large-scale mantle convection causes the migration of materials between the mantle and the crust,which leads to the variation of Earth's rotation following the law of conservation of angular momentum.When the Earth's rotation varies,relative movements occur among the plates due to their inertia and different degrees of coupling with the mantle.These relative movements inevitably cause tensile development of fractures,folds,faults and earthquakes along plate boundaries.As a result,several seismic belts have formed along these boundaries.The boundary of the Pacific Plate is the largest seismic belt in the world.Each plate has been cut up into blocks of various sizes by faults.It is the relative movement of the blocks that acts as the major driving force of intraplate earthquakes.These earthquakes are distributed mainly in areas of intermediate latitudes in the Northern Hemisphere.In short,mantle convection,variation of the Earth's rotation and plate movement are 相似文献
12.
A. V. Kiryukhin S. A. Fedotov P. A. Kiryukhin 《Journal of Volcanology and Seismology》2016,10(5):275-291
The local seismicity during the 2012–2013 eruption of Tolbachik Volcano and the 2008–2009 steam–gas eruption of Koryakskii Volcano is here considered as resulting from injections of magma that produced dikes, sills, and renewed activity at preexisting faults. We identified plane-oriented earthquake clusters in order to reveal the above zones using earthquake catalogs made at the Kamchatka Branch of the Geophysical Service of the Russian Academy of Sciences (KB GS RAS). Subsequent space–time analysis of these observations lends itself to the following interpretation. The November 27, 2012 Tolbachik lava eruption was preceded by an injection of magma resulting in a series of dikes trending west-northwestward in the range of absolute depths between–4 and +3 km in a zone situated southeast of the Ploskii Tolbachik Volcano edifice. The dikes penetrated into a nearly horizontal permeable zone at an absolute depth of approximately zero, producing sills and emplacing a magma-conducting dike along the top of the zone of cinder cones (the dip angle is 50° toward the azimuth 300°) 5.5 km from the epicenter of the initial magma injection. The summit steam–gas eruption of Koryakskii Volcano in 2008–2009 was preceded by magma filling a crustal chamber (the top of the chamber is at–3 km absolute depth; the chamber is 2.5 km across) close to the southwestern base of Koryakskii. Further, magma injection in a nearly north–south zone (7.5 by 2.5 km), the absolute depth between–2 and–5 km) in the north sector of Koryakskii Volcano was occurring concurrently with the summit steam–gas eruption. The injection of magma into the cone of Avacha Volcano (2010) produced sills (at altitudes between +1600 and +1900 m) and dikes (mostly striking northwest). 相似文献
13.
B. John Makario Londoño A. John Jairo Sanchez E. Luis Eduardo Toro Fernando Gil Cruz Olga Patricia Bohorquez 《Bulletin of Volcanology》1998,59(8):556-561
Coda Q–1 was calculated at Nevado del Ruiz Volcano (NRV) before and after two phreatomagmatic eruptions (November 1985, September
1989) and for a period of stability (May 1987) using a functional form for coda derived from a single scattering model (Sato
1977). Substantial changes were found before and after the eruptions. The highest value of Q–1 was found during the November 1985 eruption, an intermediate value for the September 1989 eruption, and the lowest value
for May 1987. It seems that the changes in coda Q–1 at NRV have a still-unknown relationship with the volume or magnitude of the eruption. A relatively strong frequency dependence
was found for all periods. Also Q–1 clearly changed with time, suggesting that the scattering was strong for the eruption of November 1985 and decreased for
the eruption of September 1989, and that the intrinsic absorption probably increased. This suggests the possibility that crystallization
is taking place in the NRV magma. The clear change of coda Q–1 before and after the eruptions at NRV also suggests the possibility that coda Q–1 is a premonitory tool of activity at this volcano.
Received: 25 October 1996 / Accepted: 21 January 1998 相似文献
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15.
George P L Walker 《Bulletin of Volcanology》1991,53(7):546-558
Tumuli are positive topographic features that are common on Hawaiian pahoehoe lava flow fields, particularly on shallow slopes, and 75 measured examples are presented here to document the size range. Tumuli form by up-tilting of crustal plates, without any crustal shortening, and are thus distinguished from pressure ridges which are up-buckled by laterally directed pressure. The axial or star-like systems of deep clefts that characterize tumuli are defined here as lava-inflation clefts; their tips advanced into red-hot lava and they widened as uplift proceeded and while the lava crust was thickening. Flat-surfaced uplifts, formed like tumuli by injection of lava under a surface crust, were previously called pressure plateaus, but lava rise is proposed instead. The pits that abound among lava rises, previously attributed to collapse or subsidence, are generally formed because the lava around them rose, and the name lava-rise pit is proposed. Unique examples of tumuli and lava rises, from which lava drained out under a surface crust 1.5 to 2.5 m thick, are described from Kilauea caldera. These examples show that in tumuli and lava rises the crust floats on considerable bodies of fluid lava, and is able to do so because of its higher vesicle content: the fluid lava loses many of its gas bubbles during residence beneath the crust. The bulk densities of samples from tumuli show a general downward increase. The form of the density profile is consistent with the relationship that for any given crustal thickness the density of fluid lava closely matched the average density of that crust, suggesting that the lava was stably density-stratified. It is inferred that stable stratification was regulated by out-flows of the more vesicular lava fractions, loss of bubbles through the lava-inflation clefts, and entry of injected lava at its level of neutral buoyancy. Below the uppermost meter the downward decrease in vesicularity closely conforms with that expected by compression of a uniform mass of gas per unit mass of lava. 相似文献
16.
Masahiko Honda David Phillips Jeff W. Harris Takuya Matsumoto 《Earth and Planetary Science Letters》2011,301(1-2):43-51
We have undertaken helium, neon and argon step-heating, isotopic analyses of eleven polycrystalline diamonds of known peridotite/eclogite paragenesis from the Jwaneng kimberlite pipe, Botswana. In contrast to the findings of crustal noble gases in framesites from the same kimberlite pipe (Honda et al., 2004. Unusual noble gas compositions in polycrystalline diamonds: preliminary results from the Jwaneng kimberlite, Botswana. Chem. Geol. 203, 347–358.), the Jwaneng polycrystalline diamonds appear to contain similar noble gas isotopic compositions (particularly Ne) to those representing a mantle source for MORBs. This implies that the Jwaneng polycrystalline diamonds may have formed in recent times, possibly close to the time of kimberlite emplacement at ~ 235 Ma. In contrast, Jwaneng framesites could be as old as gem diamonds (mineral inclusion ages of ~ 2.9 Ga). Furthermore, the data indicate that the sub-continental mantle lithosphere in the region has heterogeneous Ne isotopic compositions, or that these compositions changed over time from crustal Ne (as observed in the framesites) to MORB-like (as observed in the polycrystalline diamonds). 相似文献
17.
The occurrence of persistent organic pollutants (POPs) as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDE) in crabs Hepatus pudibundus and Callinectesdanae was assessed from two different places inside of the Santos Bay and Moela Island near one of the most economically important metropolitan areas in Southern Brazil. Among POPs analyzed, ∑PCBs (222-923 ng g(-1)lipid weight) and ∑DDTs (154-410 ng g(-1)lw) exhibited the highest concentrations in the crabs. ∑HCHs ranged from 10.3 to 30.9 ng g(-1)lw and were found in all individuals. Other OCPs found in lower concentration was Mirex (7.6-41.6 ng g(-1)lw) and HCB (5.83-16.9 ng g(-1)lw). ∑PBDEs (24.1 ng g(-1)lw) were only found in one male individual from the species C. danae collected near to the submarine sewage of Santos. Male crabs showed higher POP concentrations than female crabs for those two species. 相似文献
18.
The results of original experiments performed with a ground-based geophysical laser interferometer and a GPS-based satellite ionospheric profilometer are given. Synchronous growth was recorded for deformations of the Earth’s surface and variations in the atmospheric pressure and in the level of spatiotemporal modifications of the electron content within the ionospheric F2 layer with characteristic space scales of 102–103 km and periods of 102–103 s. The relationship between the revealed phenomena and the Earth’s seismic activity is analyzed. 相似文献
19.
This paper presents an analysis of Advanced Very High-Resolution Radiometer (AVHRR) thermal data from Shiveluch, Kliuchevskoi and Karymsky (Kamchatka, Russia) from 1993 to 2008. These different volcanoes show contrasting and variable patterns in their thermal data and lack reliable precursory thermal trends prior to large explosions. Pixel-integrated temperatures (pirT) at Shiveluch were above background during three phases: (1) 1993–1995, (2) 2001–2005 and (3) 2006–time of writing, each of which was associated with growth of an andesitic dome punctuated by explosions. The coarse spatial resolution of the AVHRR may have prevented observation of precursory thermal patterns at this volcano. Kliuchevskoi showed five phases, these show a rapid (days) or gradual (weeks to months) increase in temperature followed by rapid drop-offs, suggesting these basaltic eruptions start explosively, followed by lava effusion or vice versa. Fast magma ascent rates probably prevent the generation of thermal precursors. At Karymsky, elevated pirT values cluster into seven phases showing three trends: (1) persistently high pirT, (2) a gradual increase and decrease and (3) gradual increase followed by steep drop-offs. These trends are due to the extrusion of viscous andesitic–dacitic lava, not to Strombolian–Vulcanian activity, and show no consistent pattern prior to large explosions. PirT values at Karymsky Lake reflect the dyke intrusion that started the 1996 eruptive cycle at Karymsky. The values obtained here provide a baseline against which to monitor these volcanoes and Karymsky Lake in the future. 相似文献
20.
The Soufrière Hills Volcano, Montserrat, erupting since 18 July 1995, intensified its degassing in early 1996 with the continuing
growth of the lava dome inside the summit crater. During this period of increased activity, between 11 and 18 March 1996,
we measured gases and particles within the visible plume to determine whether at that time it posed a health risk to the population
of Plymouth, the capital town, which is 5 km southwest (downwind) and was then still occupied. Gravimetric measurements were
made of total suspended particles (TSP) and particles having an aerodynamic diameter of less than 10 μm (PM10). Measurements were made of sulphur dioxide (SO2), hydrochloric acid (HCl), hydrofluoric acid (HF), nitric acid (HNO3), acetic acid (CH3COOH), formic acid (HCOOH), and particulate sulphate (SO4
2–), chloride (Cl–), nitrate (NO3
–), fluoride (F–), methanesulphonate (CH3SO3
–), acetate (CH3COO–), formate (HCOO–), ammonium (NH4
+), sodium (Na+) and acidity (H+). Trace metals having human health implications [chromium (Cr), nickel (Ni), cobalt (Co), copper (Cu), zinc (Zn), arsenic
(As), selenium (Se), cadmium (Cd), tin (Sn), mercury (Hg) and lead (Pb)] were also determined. Mean concentrations of HCl,
SO2 and HF obtained in the town of Plymouth were 14.0, 5.9 and 0.8 ppbv, respectively. Corresponding concentrations in the mixed
plume on the crater edge were 533, 168 and 22 ppbv. There were no direct emissions of HNO3, although nitrate was detected in coarse particles at the source. Higher concentrations of CH3COOH and HCOOH were measured close to the crater. Mean TSP and PM10 were 64 and 15 μg m–3 in Plymouth, and 455 and 47 μg m–3 on the upper volcano slope. Aerosols were highly acidic at the source but rapidly neutralised during transport. Trace metals
were enriched in the aerosol relative to crater surface material. The concentrations of the acid gases, sulphur dioxide in
particular, and particles were found to be too small to pose a health hazard at the time of these measurements, when relatively
modest volcanic activity was occurring.
Received: 9 September 1998 / Accepted: 29 August 1999 相似文献