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1.
This paper demonstrates techniques for pre-eruption prediction of lahar-inundation zones in areas where a volcano has not
erupted within living memory and/or where baseline geological information about past lahars could be scarce or investigations
to delimit past lahars might be incomplete. A lahar source (or proximal lahar-inundation) zone is predicted based on ratio
of vertical descent to horizontal run-out of eruptive deposits that spawn lahars. Immediate post-eruption distal lahar-inundation
zones are predicted based on “pre-eruption” distal lahar-inundation zones and on spatial factors derived from a digital elevation
model. Susceptibility to distal lahar-inundation is estimated by weights-of-evidence, by logistic regression and by evidential
belief functions. Predictive techniques are applied using a geographic information system and are tested in western part of
Pinatubo volcano (Philippines). Predictive maps are compared with a forecast volcanic-hazard map through validation against
a field-based volcanic-hazard map. The predictive model of proximal lahar-inundation zone has “true positive” prediction accuracy,
“true negative” prediction accuracy, “false positive” prediction error and “false negative” prediction error that are similar
to those of the forecast volcanic-hazard map. The predictive models of distal lahar inundation zones have higher “true positive”
prediction accuracy and lower “false negative” prediction error than the forecast volcanic-hazard map, although the latter
has higher “true negative” prediction accuracy and lower “false positive” prediction error than the former. The results illustrate
utility of proposed predictive techniques in providing geo-information could be used, howbeit with caution, for planning to
mitigate potential lahar hazards well ahead of an eruption that could generate substantial source materials for lahar formation. 相似文献
2.
Groundwater pollution risk mapping for the Eocene aquifer of the Oum Er-Rabia basin, Morocco 总被引:2,自引:0,他引:2
Said Ettazarini 《Environmental Geology》2006,51(3):341-347
Sustainable development requires the management and preservation of water resources indispensable for all human activities. When groundwater constitutes the main water resource, vulnerability maps therefore are an important tool for identifying zones of high pollution risk and taking preventive measures in potential pollution sites. The vulnerability assessment for the Eocene aquifer in the Moroccan basin of Oum Er-Rabia is based on the DRASTIC method that uses seven parameters summarizing climatic, geological, and hydrogeological conditions controlling the seepage of pollutant substances to groundwater. Vulnerability maps were produced by using GIS techniques and applying the “generic” and “agricultural” models according to the DRASTIC charter. Resulting maps revealed that the aquifer is highly vulnerable in the western part of the basin and areas being under high contamination risk are more extensive when the “agricultural” model was applied. 相似文献
3.
Kinematics of shear bands 总被引:2,自引:2,他引:0
Dimitrios Kolymbas 《Acta Geotechnica》2009,4(4):315-318
Shear bands appear at limit states of soil bodies. They are analysed as thin zones of localised deformation that takes place
as simple (i.e. dilatant) shear. It can be observed, however, that shear bands are discontinuous and also may be “reflected”
at rigid boundaries. These phenomena appear as incompatible with the assumed shear deformation. The analysis in this paper
reveals the kinematics of such “incompatibilities” in terms of continuous deformation fields. 相似文献
4.
Landslide Hazard Zonation using Remote Sensing and GIS: a case study of Dikrong river basin, Arunachal Pradesh, India 总被引:3,自引:0,他引:3
Landslides are among the most costly and damaging natural hazards in mountainous regions, triggered mainly under the influence
of earthquakes and/or rainfall. In the present study, Landslide Hazard Zonation (LHZ) of Dikrong river basin of Arunachal
Pradesh was carried out using Remote Sensing and Geographic Information System (GIS). Various thematic layers namely slope,
photo-lineament buffer, thrust buffer, relative relief map, geology and land use / land cover map were generated using remote
sensing data and GIS. The weighting-rating system based on the relative importance of various causative factors as derived
from remotely sensed data and other thematic maps were used for the LHZ. The different classes of thematic layers were assigned
the corresponding rating value as attribute information in the GIS and an “attribute map” was generated for each data layer.
Each class within a thematic layer was assigned an ordinal rating from 0 to 9. Summation of these attribute maps were then
multiplied by the corresponding weights to yield the Landslide Hazard Index (LHI) for each cell. Using trial and error method
the weight-rating values have been re-adjusted. The LHI threshold values used were: 142, 165, 189 and 216. A LHZ map was prepared
showing the five zones, namely “very low hazard”, “low hazard”, “moderate hazard”, “high hazard” and “very high hazard” by
using the “slicing” operation. 相似文献
5.
Fezer Fritz Prof. Dr. Reichenbach Bernhard Witschel Christian MA Hell Günter Prof. Dr.-Ing. Duster Manfred Dipl.-Ing Heidrich Brigitte 《GeoJournal》1987,14(4):467-478
Airphotos have been used for topographic survey since the Twenties. The “European Space Agency” (ESA), the “Deutsche Forschungs-
und Versuchsanstalt für Luft- und Raumfahrt” (DFVLR) and “Carl Zeiss” have modified this successful technique for spacecraft
and recently have tested the system over four continents. Each of these satellite photos covers a region of 189×189 km to
the scale of 1∶800000 and may be enlarged to 1∶250000 or 1∶100000. Between the altitudes of 200 and 300 km, mapmaking or-revision
seems to be economic in zones or in countries, where existing maps are of minor quality or outdated. In this paper, examples
from deserts and semideserts in the Sudan are presented. 相似文献
6.
Characteristics of the seismicity in depth ranges 0–33 and 34–70 km before ten large and great (M
w
= 7.0−9.0) earthquakes of 2000–2008 in the Sumatra region are studied, as are those in the seismic gap zones where no large
earthquakes have occurred since at least 1935. Ring seismicity structures are revealed in both depth ranges. It is shown that
the epicenters of the main seismic events lie, as a rule, close to regions of overlap or in close proximity to “shallow” and
“deep” rings. Correlation dependences of ring sizes and threshold earthquakes magnitudes on energy of the main seismic event
in the ring seismicity regions are obtained. Identification of ring structures in the seismic gap zones (in the regions of
Central and South Sumatra) suggests active processes of large earthquake preparation proceed in the region. The probable magnitudes
of imminent seismic events are estimated from the data on the seismicity ring sizes. 相似文献
7.
N. A. Gnatus’ M. D. Khutorskoy V. K. Khmelevskoi 《Moscow University Geology Bulletin》2011,66(3):151-157
The geological-geophysical, methological, and economic aspects of extraction and utilization of petrothermal resources (“hot
dry rock thermal”) for thermal and electric energy production were considered. Heat collectors are hydraulic fracturing zones
of natural or artificially made cracks in the crystalline rocks of the basement; these rocks have higher temperature and can
be a kind of “thermal cauldron.” Detection of such “collectors” can be carried out by geophysical methods. When pumped out
of wells and warmed to 100–300°C, waters function as a heat transfer for thermal energy supply and electric energy generation.
If the technical problem of the rapid drilling of 6–10 km wells could be solved, then petrothermal energy will become competitive
with the traditional types of energy production and supply. 相似文献
8.
9.
M. Tischler H. R. Gröger B. Fügenschuh S. M. Schmid 《International Journal of Earth Sciences》2007,96(3):473-496
The interplay between the emplacement of crustal blocks (e.g. “ALCAPA”, “Tisza”, “Dacia”) and subduction retreat is a key
issue for understanding the Miocene tectonic history of the Carpathians. Coeval thrusting and basin formation is linked by
transfer zones, such as the Mid-Hungarian fault zone, which seperates ALCAPA from Tisza-Dacia. The presented study provides
new kinematic data from this transfer zone. Early Burdigalian (20.5 to ∼18.5 Ma) SE-directed thrusting of the easternmost
tip of ALCAPA (Pienides), over Tisza-Dacia is linked to movements along the Mid-Hungarian fault zone and the Periadriatic
line, accommodating the lateral extrusion of ALCAPA. Minor Late Burdigalian (∼18.5 to 16 Ma) NE-SW extension is interpreted
as related to back-arc extension. Post Burdigalian (post-16 Ma) NE–SW shortening and NW–SE extension correlate with “soft
collision” of Tisza-Dacia with the European foreland coupled with southward migration of active subduction. During this stage
the Bogdan-Voda and Dragos-Voda faults were kinematically linked to the Mid-Hungarian fault zone. Sinistral transpression
(16 to 12 Ma) at the Bogdan-Voda fault was followed by sinistral transtension (12–10 Ma) along the coupled Bogdan-Dragos-Voda
fault system. During the transtensional stage left-lateral offset was reduced eastwards by SW trending normal faults, the
fault system finally terminating in an extensional horse-tail splay. 相似文献
10.
Chemodynamics of trace metal fractions in surface sediments of the Pandoh Lake,Lesser Himalaya,India
Anshumali A. L. Ramanathan Gurdeep Singh Gurmeet Singh Rajesh Ranjan Parijat Tripathi 《Environmental Geology》2009,57(8):1865-1879
The seasonal variation in the trace metals’ concentrations (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn) were investigated in surface
sediments of the Pandoh Lake. The horizontal distribution of TC, TN, and TP reflects spatial and temporal differences in sedimentary
organic production. The chemical sequential extraction of heavy metals was carried out by seven-step fractionation scheme
(Leleyter and Probst in Int J Environ Chem 73:109–128, 1999). The significant concentrations of Ni and Cd were associated with “water soluble (Eua)” fraction in the monsoon and winter,
respectively, while “exchangeable (Exch)” and “carbonate-bound (Carb)” fractions for Ni and Cd were abundant in winter and
summer. The Cd, Cu, and Pb associated with “Exch” fraction in the summer season support their availability on exchange sites
due to oxidized nature of surface sediments. Enrichment of Co, Fe, Mn, and Zn in “AFeO” fraction showed poor bioavailability,
while Cd, Cu, and Mn in the monsoon, Co in the winter and summer, and Zn in the winter season showed significant “organically
bound (Org)” fraction. The ANOVA was significant for chemical fractions of trace elements except “Carb” fraction of Pb and
Zn and “CFeO” fraction of Pb. Factor analysis revealed that the “Eua”, “Exch”, and “Carb” fractions together control the metal
enrichment of “MnO”, “AFeO”, and “CFeO” fractions in the summer season. 相似文献
11.
In this work some examples of “twisting” of the Earth in the geologic past are given: displacement of the northern parts of
the global submeridional structures to the west relative to their southern parts; the rotation of the “geodynamic pair” of
Siberia-Laurentia in the Proterozoic; sinistral displacement of the Northern Hemisphere relative to the Southern Hemisphere
after the collapse of the last Pangaea; the equatorial rotation of the continental plates; oblique orientation of the global
network of planetary fracturing; an inclination of the axis of submeridional compression; sinistral “beveling”; the dextral
“twisting” of Venus. All these examples confirm the idea of possible sinistral “twisting” of the Earth that has been proposed
by many authors. The cause of such “twisting” is unclear, although it is likely connected with the Earth’s rotation around
its axis. Some of these examples show that many paleomagnetic reconstructions can be usefully discussed in a tectonophysical
aspect. Moreover, in connection with this data, the development of a new scientific field, called “paleomagnetic tectonophysics”, is possible. 相似文献
12.
M. D. Khutorskoi L. V. Podgornykh O. I. Suprunenko B. I. Kim A. A. Chernykh 《Doklady Earth Sciences》2011,440(2):1381-1386
2D and 3D geotemperature models of the sedimentary cover within the Laptev Sea shelf have been calculated. The presence of
several “thermal domes” (zones of uplifted isotherms) has been found. Based on analogous sedimentary basins with domes, which
correlate to the location of hydrocarbon deposits, the forecasting has been made that the Ust-Lena graben and Omoloi trough
are the most promising areas for oil-and-gas prospecting. 相似文献
13.
Summary ?Results of experimental investigations in the dry system PtS-PdS-NiS at 1100°C, 1000°C, and 900°C are presented. The phases
observed at 1100°C are “cooperite” and a melt, at 1000°C “cooperite”, “braggite”, and a melt and at 900°C “cooperite”, “braggite”,
“vysotskite”, Ni1−xS, and a melt. At 1100°C the maximum solubility of Ni in ideal, Pd-free “cooperite” is 2.7 atomic per cent and the Pd-content
limit in Ni-free “cooperite” is 12.8 atomic per cent. At 1000°C the maximum solubility of Ni in ideal, Pd-free “cooperite”
is 3.3 atomic per cent and the Pd-content in Ni-free “cooperite” is 13.7 atomic per cent. The “braggite” composition ranges
from Pt0.56Pd0.38Ni0.06S and Pt0.59Pd0.41S in a Ni-saturated and Ni-free environment respectively to Pt0.18Pd0.80Ni0.02S and Pt0.14Pd0.86S respectively. At 900°C the maximum Ni-content in ideal Pd-free “cooperite” is 3.1 atomic per cent and the Pd-limit in Ni-free
“cooperite” is 12.5 atomic per cent. The “braggite” composition ranges from Pt0.59Pd0.29Ni0.12S and Pt0.60Pd0.40S for a Ni-saturated and Ni-free environment respectively, to Pd0.91Ni0.09S and PdS respectively. The Ni-content in “braggite” and “vysotskite” increases slightly with increasing Pt/Pd ratios and
is higher at 900°C than at 1000°C. Comparison of experimental trends with cooperite, braggite, and vysotskite analyses from
the literature implies high temperatures of formation for Pt-Pd-Ni sulphides in placers if Ni-saturation is assumed.
Received October 1, 1998;/revised version accepted September 7, 1999 相似文献
Zusammenfassung ?Synthetischer ,,Cooperit”, ,,Braggit” und “Vysotskit” im System PtS-PdS-NiS bei 1100°C, 1000°C und 900°C Ergebnisse experimenteller Untersuchungen im trockenen System PtS-PdS-NiS bei 1100°C, 1000°C und 900°C werden dargestellt. Bei 1100°C sind die Phasen “Cooperit” und Schmelze, bei 1000°C “Cooperit”, “Braggit” und Schmelze und bei 900°C “Cooperit”, “Braggit”, “Vysotskit”, Ni1−xS und Schmelze stabil. Bei 1100°C ist die maximale L?slichkeit von Ni in idealem, Pd-freiem “Cooperit” 2.7 Atomprozent und der Pd-Gehalt in Ni-freien “Cooperit” liegt bei maximal 12.8 Atomprozent. Bei 1000°C ist die maximale L?slichkeit von Ni in idealem, Pd-freien “Cooperit” 3.3 Atomprozent und der Pd-Gehalt in Ni-freien “Cooperit” liegt bei maximal 13.7 Atomprozent. Die Zusammensetzung des “Braggits” variiert zwischen Pt0.56Pd0.38Ni0.06S und Pt0.18Pd0.80Ni0.02S in einem Ni-ges?ttigtem und zwischen Pt0.59Pd0.41S und Pt0.14Pd0.86S in einem Ni-freien Umfeld. Bei 900°C liegt die maximale L?slichkeit von Ni in idealem Pd-freien “Cooperit” bei 3.1 Atomprozent und der Pd-Gehalt in Ni-freien “Cooperit” liegt bei maximal 12.5 Atomprozent. Die Zusammensetzung des “Braggits” variiert zwischen Pt0.59Pd0.29Ni0.12S und Pd0.89Ni0.08S in einem Ni-ges?ttigten und zwischen Pt0.59Pd0.40S und PdS in einem Ni-freien Umfeld. Der Nickelgehalt in “Braggit” und “Vysotskit” nimmt mit zunehmendem Pt/Pd Verh?ltnis zu und ist bei 900°C h?her als bei 1000°C. Ein Vergleich der experimentellen Trends mit Cooperit, Braggit und Vysotskit Analysen aus der Literatur weist auf eine Hochtemperaturbildung der Pt-Pd-Ni Sulfide in Seifenlagerst?tten hin, wenn man von Nickels?ttigung ausgeht.
Received October 1, 1998;/revised version accepted September 7, 1999 相似文献
14.
Chlorite-rich ultramafic reaction zones in Colorado Plateau xenoliths: recorders of sub-Moho hydration 总被引:5,自引:0,他引:5
Douglas Smith 《Contributions to Mineralogy and Petrology》1995,121(2):185-200
Three chlorite-rich and one garnet-pyroxenite xenolith from the diatreme at Moses Rock, Utah, document storage and transport
of water and consequent metasomatism in the mantle within the stability field of garnet peridotite, probably at depths of
at least 75 km. Three mineral assemblages are present in zones in one chlorite-rich xenolith: in that xenolith, an assemblage
of chlorite+enstatite+diopside+ ilmenite+titanian chondrodite is separated by diop- side+“talc” from an assemblage of chlorite+diopside+ilmenite+pyrite.
Euhedral grains of enstatite (0.02% Al2O3, 0.05% CaO)+diopside record low temperatures, and high Mn/Fe in these pyroxenes was caused by growth in chlorite-dominated
rock. Derivation from garnet lherzolite is established by relict pyrope (Py71Gr11Alm18). The “talc” has Fe/Mg unusually high relative to that of associated chlorite, and electron probe analyses of the “talc”
sum low, consistent with excess water; the unusual composition may be due solely to alteration and consequent submicroscopic
intergrowths of other phases, but the “talc” could be an analogue of the high-pressure synthetic 10-Å phase. Garnet pyroxenite
has a retrograde assemblage of chlorite-garnet-omphacite. The chlorite-rich rocks formed at contacts between garnet peridotite
and other mantle rock in response to fluid flow. Pressures ≥2.2 GPa are consistent with stability of enstatite + aqueous fluid
and of diopside + talc, with the occurrence of titanian chondrodite, and with the stability of garnet lherzolite. A chlorite
separate has δ18O=6.9, consistent with mantle hydration. The small-scale reaction zones could have formed in a geologically brief time, plausibly
just before eruption at about 25 Ma, and the responsible fluids probably also catalyzed recrystallization of associated eclogites.
The hydration may have been restricted to shear zones that traversed the lower crust and the mantle to at least 75 km depth.
The chlorite-rich rocks may be from the deepest part of the mantle that was sampled by the diatreme eruption. Chlorite-garnet
pairs in garnet pyroxenites and pyrope megacrysts yield temperatures in the range 410–510° C. Low temperatures in the mantle of the Colorado Plateau are consistent with an unusually low mantle heat flux and with
cooling of lithosphere by an underlying subducted slab.
Received: 14 April 1994/Accepted: 23 December 1994 相似文献
15.
Geological, methodological, and economic aspects of the production and utilization of petrother mal resources (heat of “dry”
rocks) for electric energy production and heat supply are considered. Possibility of the utilization of natural fracture zones
or artificial fissure zones, which are created by hydraulic fracturing of underground rock massifs, is noted. Application
of new tools for drilling deep wells makes the petrochemical energy competitive relative to both other types of renewable
resources and traditional organic fuel. 相似文献
16.
Comparison of Mathematical Methods of Potential Modeling 总被引:1,自引:0,他引:1
Helmut Schaeben 《Mathematical Geosciences》2012,44(1):101-129
Various attempts are known to turn the “catalogue” of mineral deposit models compiled by Cox and Singer (1986) operational, and have initiated activities called “potential mapping”, “potential modeling”, or “targeting”. The common
ultimate objective is to estimate the probability for a given location that a mineralization of a given type occurred. The
mathematics range from “weights of evidence” and others featuring a Bayesian approach to logistic regression by maximum likelihood,
and include other realizations by means of fuzzy methods, genetic programming, and artificial neural nets. Once developed
and coded, applications are not restricted to mineral prospection and exploration but include any kind of occurrences and
their estimated probabilities, e.g., risk assessment of land slides and many others. 相似文献
17.
Indrajit Pal Sankar Kumar Nath Khemraj Shukla Dilip Kumar Pal Abhishek Raj K. K. S. Thingbaijam B. K. Bansal 《Natural Hazards》2008,45(3):333-377
An earthquake hazard zonation map of Sikkim Himalaya is prepared using eight thematic layers namely Geology (GE), Soil Site
Class (SO), Slope (SL), Landslide (LS), Rock Outcrop (RO), Frequency–Wavenumber (F–K) simulated Peak Ground Acceleration (PGA),
Predominant Frequency (PF), and Site Response (SR) at predominant frequencies using Geographic Information System (GIS). This
necessitates a large scale seismicity analysis for seismic source zone classification and estimation of maximum earthquake
magnitude or maximum credible earthquake to be used as a scenario earthquake for a deterministic or quasi-probabilistic seismic
scenario generation. The International Seismological Center (ISC) and Global Centroid Moment Tensor (GCMT) catalogues have
been used in the present analysis. Combining b-value, fractal correlation dimension (Dc) of the epicenters and the underlying tectonic framework, four seismic source zones
are classified in the northeast Indian region. Maximum Earthquake of M
W 8.3 is estimated for the Eastern Himalayan Zone (EHZ) and is used to generate the seismic scenario of the region. The Geohazard
map is obtained through the integration of the geological and geomorphological themes namely GE, SO, SL, LS, and RO following
a pair-wise comparison in an Analytical Hierarchy Process (AHP). Detail analysis of SR at all the recording stations by receiver
function technique is performed using 80 significant events recorded by the Sikkim Strong Motion Array (SSMA). The ground
motion synthesis is performed using F–K integration and the corresponding PGA has been estimated using random vibration theory
(RVT). Testing for earthquakes of magnitude greater than M
W 5, a few cases presented here, establishes the efficacy and robustness of the F–K simulation algorithm. The geohazard coverage
is overlaid and sequentially integrated with PGA, PF, and SR vector layers, in order to evolve the ultimate earthquake hazard
microzonation coverage of the territory. Earthquake Hazard Index (EHI) quantitatively classifies the terrain into six hazard
levels, while five classes could be identified following the Bureau of Indian Standards (BIS) PGA nomenclature for the seismic
zonation of India. EHI is found to vary between 0.15 to 0.83 quantitatively classifying the terrain into six hazard levels
as “Low” corresponding to BIS Zone II, “Moderate” corresponding to BIS Zone III, “Moderately High” belonging to BIS Zone IV,
“High” corresponding to BIS Zone V(A), “Very High” and “Severe” with new BIS zones to Zone V(B) and V(C) respectively. 相似文献
18.
The sediment-hosted disseminated gold deposits in the Oinling region are of sedimentation-slight-metamorphic origin superimposed by hydrothermal reworking at moderate-low temperatures and are well comparable with the typical Carlin gold deposits in the United States.In view of the confusing concept concerning the “sediment-hosted”and “Carlin-type” gold deposits,the authors propose that the term“sediment-hosted gold deposit”should be used in a broad sense which encompasses at least the four subtypes,i.e.,the Carlin type,the metamorphic fine clastic type,the hydrothermal sedimentary type and the vein type.In oter words,the “Carlin-type”should not be used as a synonym for “sediment-hosted”but is recommended as a subtype under the general category of “sediment-hosted gold deposits” 相似文献
19.
Entropies of Al-Si in layer silicates have been calculated using a series of CVM approximations for the honeycomb lattice.
The parameters of the models have been constrained by 29Si NMR data. The results of low order approximations such as “pair” and “star” have been rejected because of their low accuracy
at high Al/(Al+Si) ratios. Reasonably accurate results have been achieved with the help of the “hexagon” and “star-hexagon”
approximations.
Received: 31 October 1997 / Revised, accepted: 17 April 1998 相似文献
20.
There is growing recognition among political ecologists of the need to examine shifting natural resource regimes and their
effects on livelihoods in “First World” places. This emerging literature has variously examined the “Third World within,”
the persistence of “subsistence activities” in the “First World,” and the “reterritorialization” of land tenure and access.
However, much of this work has tended to focus on traditional extractive industries in the American West, indigenous claims
to lands and resources in the U.S. and Canada, and non-timber resources on public lands. In contrast, we use a case study
of African-American sweetgrass basket-makers, associated with the Gullah culture, in South Carolina’s lowcountry to examine
the ways in which ongoing amenity-driven residential development is fundamentally reshaping resource access on private lands.
Historically, basket-makers harvested the materials (primarily sweetgrass or Mulenbergia filipes) needed for their culturally
important art form from accessible, rural, and privately held tracts of land in close proximity to their communities, but
development pressures and changes in resident interpretation of property rights has decreased access to basket-making resources.
The case is particularly illuminating, as it examines the emergence of ‘conservation subdivisions’ in the region and raises
important questions about what “rural uses” and users are being conserved through responses to exurban, suburban, and urban
development in formerly rural areas. 相似文献