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31.
A swarm of earthquakes of magnitudes up to M
L = 3.8 stroke the region of West Bohemia/Vogtland (border area between Czechia and Germany) in October 2008. It occurred in
the Novy Kostel focal zone, where also all recent earthquake swarms (1985/1986, 1997, and 2000) took place, and was striking
by a fast sequence of macroseismically observed earthquakes. We present the basic characteristics of this swarm based on the
observations of a local network WEBNET (West Bohemia seismic network), which has been operated in the epicentral area, on
the Czech territory. The swarm was recorded by 13 to 23 permanent and mobile WEBNET stations surrounding the swarm epicenters.
In addition, a part of the swarm was also recorded by strong-motion accelerometers, which represent the first true accelerograms
of the swarm earthquakes in the region. The peak ground acceleration reached 0.65 m/s2. A comparison with previous earthquake swarms indicates that the total seismic moments released during the 1985/1986 and
2008 swarms are similar, of about 4E16 Nm, and that they represent the two largest swarms that occurred in the West Bohemia/
Vogtland region since the M
L = 5.0 swarm of 1908. Characteristic features of the 2008 swarm are its short duration (4 weeks) and rapidity and, consequently,
the fastest seismic moment release compared to previous swarms. Up to 25,000 events in the magnitude range of 0.5 < M
L < 3.8 were detected using an automatic picker. A total of nine swarm phases can be distinguished in the swarm, five of them
exceeding the magnitude level of 2.5. The magnitude–frequency distribution of the complete 2008 swarm activity shows a b value close to 1. The swarm hypocenters fall precisely on the same fault portion of the Novy Kostel focal zone that was activated
by the 2000 swarm (M
L ≤ 3.2) in a depth interval from 6 to 11 km and also by the 1985/1986 swarm (M
L ≤ 4.6). The steeply dipping fault planes of the 2000 and 2008 swarms seem to be identical considering the location error
of about 100 m. Furthermore, focal mechanisms of the 2008 swarm are identical with those of the 2000 swarm, both matching
an average strike of 170° and dip of 80° of the activated fault segment. An overall upward migration of activity is observed
with first events at the bottom and last events at the top of the of the activated fault patch. Similarities in the activated
fault area and in the seismic moments released during the three largest recent swarms enable to estimate the seismic potential
of the focal zone. If the whole segment of the fault plane was activated simultaneously, it would represent an earthquake
of M
L ~5. This is in good agreement with the estimates of the maximum magnitudes of earthquakes that occurred in the West Bohemia/Vogtland
region in the past. 相似文献
32.
We present the pattern of seismic activity in the period between 2001 and 2007 for the Novy Kostel focal zone, which is recently
the most active zone of the West-Bohemia/Vogtland earthquake swarm region. While the year 2001 was characterized by dying
out of the 2000-swarm activity in the form of a few microswarms, almost no seismicity occurred in the period between 2002
and 2003. Since 2004 an elevated seismic activity occurs in the form of repeating microearthquake swarms. We used a relative
location method to relate the hypocenter positions of the post-swarm activity to the geometry of the 2000-swarm cluster. We
found that the activity has concentrated in several clusters, which have been repeatedly activated. Some clusters coincide
with the position of the previous activity; the others have activated so far inactive deep segments at the southern edge of
the Novy Kostel fault. Besides the shift of the hypocenters to the edges of the previously active area we observe a southward
migration of the activity and an increase of maximum depths of earthquakes from 10 to 13 km. The waveform similarity analysis
disclosed that some fault patches consist of only a single, repeatedly activated fault plane, while the others consist of
multiple, differently oriented fault planes activated almost simultaneously. Most of the focal mechanisms are consistent with
the geometry of hypocenters showing NNW-SSE trending steep fault planes with left-lateral strike-slip mechanisms and varying
dip-slip component. 相似文献
33.
One‐dimensional flow simulations were conducted at four locations of the shallow alluvial aquifer of the upper Rhine River (at the Erstein polder) to quantify the time‐dependent moisture distribution, the water flux and the water volume infiltrated in the unsaturated zone as a function of soil heterogeneities during a five‐day‐long flooding event. Three methods of estimating the hydraulic parameters of soil in the vadose zone were tested. They are based on the following: (1) experimental data, (2) soil particle‐size distribution and (3) pedology information on soils. Water fluxes calculated from modelling approaches 2 and 3 were compared with those of the experiment‐based values and the effect of these differences on the arrival time and velocity of water at the water table were analysed. Major differences in water fluxes were found among the methods of estimating the hydrodynamic parameters. At the Terrace location, the groundwater recharge predicted using soil data from methods 1 and 2 are approximately 4500 and 2400 mm, respectively. Flow simulations using soil data and the experiment‐based method show the highest velocities of infiltrating water at the soil surface and largest volume of groundwater infiltration but result in the lowest centres of the moisture content mass. The results obtained using soil data based on the pedological method are similar to those calculated using soil parameters based on the particle‐size distribution of extracted soil samples. Water pressure profiles calculated on Terrace and Channel location, 3 and 7 days after the inundation event agreed reasonably well with those observed when using hydrodynamic parameters from the experiment‐based method. However, the flow model using the pedology‐based parameters largely underestimates the time needed to achieve hydrostatic conditions of the soil water profile once water flooding at the soil surface stops. This can be mainly attributed to the low values of estimated van Genuchten parameter α. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
34.
Giacomo BRIANI Matthieu GOUNELLE Michèle BOUROT‐DENISE Michael E. ZOLENSKY 《Meteoritics & planetary science》2012,47(5):880-902
Abstract– Xenoliths are inclusions of a given meteorite group embedded in host meteorites of a different group. Xenoliths with dimensions between a few μm and about 1 mm (microxenoliths) are “meteorite‐trapped” analogues of micrometeorites collected on the Earth. However, they have the unique features of sampling the zodiacal cloud (1) at more ancient times than those sampled by micrometeorites and (2) at larger distances from the Sun (corresponding to the asteroid Main Belt) than that sampled by micrometeorites (1 AU). Herein we describe a systematic search for new xenoliths and microxenoliths in H chondrites, aimed at determining their abundance in these ordinary chondrites, analyzing their mineralogy, and searching for possible correlations with host meteorite properties. Sixty‐six sections from 40 meteorites have been analyzed. Twenty‐four new xenoliths have been discovered. About 87% of them are microxenoliths (i.e., <1 mm), only three are >1 mm in their largest dimension. All the newly discovered xenoliths and microxenoliths are composed of carbonaceous chondritic material. Hence, the zodiacal cloud was dominated by carbonaceous material even in past epochs. All the new xenoliths and microxenoliths have been found in regolith breccias. Hydrous‐phase‐rich xenoliths and microxenoliths in H4 and H5 chondrites attest that their embedding happened after the end of the thermal metamorphism. All these data suggest that xenoliths and microxenoliths were embedded when their host meteorites were part of the parent body regolith. This, combined with the H chondrite impact age distribution, attests that the embedding may have happened as early as 3.5 Gyr ago. 相似文献
35.
Structure,composition, and location of organic matter in the enstatite chondrite Sahara 97096 (EH3) 总被引：1，自引：0，他引：1
Laurette PIANI François ROBERT Olivier BEYSSAC Laurent BINET Michèle BOUROT‐DENISE Sylvie DERENNE Corentin LE GUILLOU Yves MARROCCHI Smail MOSTEFAOUI Jean‐Noël ROUZAUD Aurélien THOMEN 《Meteoritics & planetary science》2012,47(1):8-29
Abstract– The insoluble organic matter (IOM) of an unequilibrated enstatite chondrite Sahara (SAH) 97096 has been investigated using a battery of analytical techniques. As the enstatite chondrites are thought to have formed in a reduced environment at higher temperatures than carbonaceous chondrites, they constitute an interesting comparative material to test the heterogeneities of the IOM in the solar system and to constrain the processes that could affect IOM during solar system evolution. The SAH 97096 IOM is found in situ: as submicrometer grains in the network of fine‐grained matrix occurring mostly around chondrules and as inclusions in metallic nodules, where the carbonaceous matter appears to be more graphitized. IOM in these two settings has very similar δ15N and δ13C; this supports the idea that graphitized inclusions in metal could be formed by metal catalytic graphitization of matrix IOM. A detailed comparison between the IOM extracted from a fresh part and a terrestrially weathered part of SAH 97096 shows the similarity between both IOM samples in spite of the high degree of mineral alteration in the latter. The isolated IOM exhibits a heterogeneous polyaromatic macromolecular structure, sometimes highly graphitized, without any detectable free radicals and deuterium‐heterogeneity and having mean H‐ and N‐isotopic compositions in the range of values observed for carbonaceous chondrites. It contains some submicrometer‐sized areas highly enriched in 15N (δ15N up to 1600‰). These observations reinforce the idea that the IOM found in carbonaceous chondrites is a common component widespread in the solar system. Most of the features of SAH 97096 IOM could be explained by the thermal modification of this main component. 相似文献
36.
Silveira Mariana V. Casagrande Michéle D. T. 《Geotechnical and Geological Engineering》2021,39(5):3875-3887
Geotechnical and Geological Engineering - This paper presents the results of an experimental program about the behavior and durability of soils reinforced with randomly distributed vegetal fibers... 相似文献
37.
Pierre ROCHETTE Jérôme GATTACCECA Michèle BOUROT‐DENISE Guy CONSOLMAGNO Luigi FOLCO Tomas KOHOUT Lauri PESONEN Leonardo SAGNOTTI 《Meteoritics & planetary science》2009,44(3):405-427
Abstract— A database of magnetic susceptibility measurements of stony achondrites (acapulcoite‐lodranite clan, winonaites, ureilites, angrites, aubrites, brachinites, howardite‐eucrite‐diogenite (HED) clan, and Martian meteorites, except lunar meteorites) is presented and compared to our previous work on chondrites. This database provides an exhaustive study of the amount of iron‐nickel magnetic phases (essentially metal and more rarely pyrrhotite and titanomagnetite) in these meteorites. Except for ureilites, achondrites appear much more heterogeneous than chondrites in metal content, both at the meteorite scale and at the parent body scale. We propose a model to explain the lack of or inefficient metal segregation in a low gravity context. The relationship between grain density and magnetic susceptibility is discussed. Saturation remanence appears quite weak in most metal‐bearing achondrites (HED and aubrites) compared to Martian meteorites. Ureilites are a notable exception and can carry a strong remanence, similar to most chondrites. 相似文献
38.
Michèle Moons 《Celestial Mechanics and Dynamical Astronomy》1996,65(1-2):175-204
The study of mean motion resonance dynamics was motivated by the search for an explanation for the puzzling problem of the Kirkwood gaps. The most important contributions in this field within the last 32 years are reviewed here. At the beginning of that period, which coincides with the first long-term numerical investigations of resonant motion, different hypotheses (collisional, gravitational, statistical and cosmological) to explain the origin of the gaps were still competing with each other. At present, a general theory, based on gravitational mechanisms only, is capable of explaining in a uniform way all the Kirkwood gaps except the 2/1 one. Indeed, in the 4/1, 3/1, 5/2 and 7/3 mean motion commensurabilities, the overlap of secular resonances leads to almost overall chaos where asteroids undergo large and wild variations in their orbital elements. Such asteroids, if not thrown directly into the Sun, are sooner or later subject to strong close encounters with the largest inner planets, the typical time scale of the whole process being of the order of a few million years. Unfortunately, this mechanism is not capable of explaining the 2/1 gap where the strong chaos produced by the overlapping secular resonances does not attain orbits with moderate eccentricity, of low inclination and with low to moderate amplitude of libration. In the light of the most recent studies, it appears that the 2/1 gap is the global consequence of slow diffusive processes. At present, the origin of these processes remains under study. 相似文献
39.
Frédéric Villiéras Laurent J. Michot Frédérique Bardot Manuel Chamerois Céline Eypert-Blaison Michèle François Gilles Gérard Jean-Maurice Cases 《Comptes Rendus Geoscience》2002,334(9):597-609
The precise study of adsorption mechanisms at solid–liquid interfaces requires a good analysis of the surface heterogeneity of the studied solids. For that purpose, molecular probe technique is one of the most powerful, especially at solid–gas interfaces. Indeed, low-pressure gas adsorption coupled to modelling of derivative adsorption isotherms as a function of logarithm of pressure allows to study qualitatively and quantitatively the effect of surface heterogeneity on the energy distribution of adsorption centres. The present review points out the interests of that approach to determine the shape of particles, the presence of high-energy adsorption sites and the surface polarity. Results comparing adsorption at solid–gas and solid–liquid interfaces are also mentioned. To cite this article: F. Villiéras et al., C. R. Geoscience 334 (2002) 597–609. 相似文献
40.
Daniel?BernoulliEmail author Urs?Schaltegger Willem?B.?Stern Martin?Frey? Michèle?Caron Simonetta?Monechi 《International Journal of Earth Sciences》2004,93(3):384-399
At Montagna della Maiella and at Gola del Furlo (central Apennines) two discrete layers of bentonic clay are intercalated within the pelagic (Furlo) and turbiditic/pelagic limestones (Maiella) of the Upper Cretaceous basinal succession of the Umbrian basin (Scaglia facies). The bentonite layers are dated by planktonic foraminifera to the Globotruncanita elevata zone, early Campanian, and by calcareous nannofossils to the Aspidolithus parcus zone (CC 18); they fall into the reversed interval of chron 33. Detailed correlation shows the layers to be of exactly the same age. The upper layer is dated by U/Pb on magmatic zircons to 81.67±0.21 Ma, an age compatible with the Cretaceous time-scale of Obradovich. The mineralogy of the bentonitic clays is almost pure montmorillonite and contrasts sharply with the clay mineral assemblage of the enclosing pelagic and turbiditic limestones, which is dominated by soil-derived smectite and illite in different proportions. The bentonite seams are interpreted as the submarine alteration products of wind-borne volcanic ashes. They can be followed with only minor changes in thickness over 200 km and must be derived from distant volcanic sources and related to extreme volcanic events. A possible source area is present in the Dinarides where Upper Cretaceous subduction-related magmatic rocks are widespread. 相似文献