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1.
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
2.
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
3.
The slow spreading mid-Indian Ocean ridge system containing the Carlsberg, Central and Southwest Indian ridges is seismically
very active. In the present study, a detailed analysis has been carried out of the data of earthquake sources along different
ridge segments in order to investigate the spatial and temporal clustering patterns and to evaluate crustal processes related
to the swarm occurrences along these ridges. The spatial and temporal clustering pattern of the recent earthquakes (1980–1990)
pertaining to nine major spreading segments and eight fracture zones suggests that the events cluster in greater proportion
along the spreading segments than along the fracture zones.
We performed a systematic search of earthquake catalogue during the period 1964–1990 by examining the spatio-temporal hypocentral
clusters in order to identify the swarm occurrences along these ridges. The search included eighteen prominent sequences,
of which, thirteen were earthquake swarms. Except two, all other swarms were found to be occurring mainly on the spreading
segments. The maximum magnitude observed in these swarms is mb = 5.4 and have many events predominantly showing normal faulting mechanisms. The spatial disposition and temporal activity
of the events in swarms is much similar to the foreshock-mainshock-aftershock sequences observed along the spreading rift
valley zones. These characteristics help us to support that swarms along the slow spreading mid-Indian Ocean ridges are the
result of extensional tectonic activity, leading to the development of the median valley topography, a mechanism similar to
that proposed by Bergman and Solomon (1990) for the Mid-Atlantic Ridge. 相似文献
4.
The Andaman-Sumatra subduction zone is seismically one of the most active and complex subduction zones that produced the 26
December 2004 mega thrust earthquake (Mw 9.3) and large number of aftershocks. About 8,000 earthquakes, including more than
3,000 aftershocks (M ≥ 4.5) of the 2004 earthquake, recorded during the period 1964–2007, are relocated by the EHB method. We have analysed this
large data set to map fractal correlation dimension (Dc) and frequency-magnitude relation (b-value) characteristics of the seismogenic structures of this ~3,000-km-long mega thrust subduction zone in south-east Asia.
The maps revealed the seismic characteristics of the Andaman-Sumatra-Java trenches, West Andaman fault (WAF), Andaman Sea
Ridge (ASR), Sumatra and Java fault systems. Prominent N–S to NW–SE to E–W trending fractal dimension contours all along the
subduction zone with Dc between 0.6 and 1.4 indicate that the epicentres mostly follow linear features of the major seismogenic
structures. Within these major contours, several pockets of close contours with Dc ~ 0.2 to 0.6 are identified as zones of
epicentre clusters and are inferred to the fault intersections as well as asperity zones along the fault systems in the fore
arc. A spatial variation in the b-value (1.2–1.5) is also observed along the subduction zone with several pockets of lower b-values (1.2–1.3). The smaller b-value zones are corroborated with lower Dc (0.5–0.9), implying a positive correlation. These zones are identified to be the
zones of more stress or asperity where rupture nucleation of intermediate to strong magnitude earthquakes occurred. 相似文献
5.
First Order Seismic Microzonation of Delhi,India Using Geographic Information System (GIS) 总被引：2，自引：4，他引：2
William K. Mohanty M. Yanger Walling Sankar Kumar Nath Indrajit Pal 《Natural Hazards》2007,40(2):245-260
A first order seismic microzonation map of Delhi is prepared using five thematic layers viz., Peak Ground Acceleration (PGA)
contour, different soil types at 6 m depth, geology, groundwater fluctuation and bedrock depth, integrated on GIS platform.
The integration is performed following a pair-wise comparison of Analytical Hierarchy Process (AHP), wherein each thematic
map is assigned weight in the 5-1 scale: depending on its contribution towards the seismic hazard. Following the AHP, the
weightage assigned to each theme are: PGA (0.333), soil (0.266), geology (0.20), groundwater (0.133) and bedrock depth (0.066).
The thematic vector layers are overlaid and integrated using GIS. On the microzonation theme, the Delhi region has been classified
into four broad zones of vulnerability to the seismic hazard. They are very high (> 52%), high (38–52%), moderate (23–38%)
and less ( < 23%) zones of seismic hazard. The “very high” seismic hazard zone is observed where the maximum PGA varies from
140 to 210 gal for a finite source model of Mw 8.5 in the central seismic gap. A site amplification study from local and regional earthquakes for Delhi region using Delhi
Telemetry Network data shows a steeper site response gradient in the eastern side of the Yamuna fluvial deposits at 1.5 Hz.
The ‘high’ seismic hazard zone occupies most of the study area where the PGA value ranges from 90 to 140 gal. The ‘moderate’
seismic hazard zone occurs on either side of the Delhi ridge with PGA value varying from 60 to 90 gal. The ‘less’ seismic
hazard zone occurs in small patches distributed along the study area with the PGA value less than 60 gal. Site response studies,
PGA distribution and destruction pattern of the Chamoli earthquake greatly corroborate the seismic hazard zones estimated
through microzonation on GIS platform and also establishes the methodology incorporated in this study. 相似文献
6.
Sebastiano Imposa Francesco Barone Domenico Bella Massimo Cristaldi Stefano Gresta 《Environmental Earth Sciences》2011,64(7):1777-1786
A “standard procedure” to characterize the seismic hazard of a given area was proposed. It is based on a multidisciplinary
approach implying: (1) the knowledge of the seismic history of the area; (2) detailed geological surveys; (3)seismic noise
measurements; (4) simulations of earthquake scenarios. The downtown of Acireale, a typical baroque town located on Eastern
Sicily, was chosen as the “test area”. A catalog of the local seismogenic faults (able to generate earthquakes in historical
times) has been compiled, as well as a seismic catalog for the effects of both local and regional earthquakes. The analysis
of both catalogs allowed us to make the following conclusions: (1) the most important seismogenic faults affecting the Acireale
municipality do not affect the downtown, while the related local earthquakes attenuate their energy (and intensity) in short
(few km) distances; (2) the highest seismic intensity (degree X) experienced in Acireale downtown was caused by the 1693 regional earthquake; (3) over the last 140 years, the downtown has
experienced the highest intensity value of VII only once, while six times the intensity was VI. On the whole, this implies
a moderate seismic hazard. The estimation of the seismic hazard has been also approached by the experimental method of recording
seismic noise. Measurements have been performed at seven different sites, where drills gave detailed information on the shallow
subsurface geology to obtain HV (horizontal/vertical) spectral ratios. On the whole, the highest site amplification factor
was moderate (about 7). A further investigation based on synthetic seismograms (and spectra) produced by simulating two given
earthquake scenarios was also performed. The two scenarios are, respectively, representative of the largest expected earthquake
in the area (the 1693 shock) and of a moderate (magnitude ca. 5.5) local earthquake (as the 1818 one). Moderate to strong
locally expected accelerations were evidenced. 相似文献
7.
Based on the investigation of samples recovered during Cruise 25 of the R/V “Akademik Nikolai Strakhov,” the character of
magmatism was determined in the flank parts of the rift zone at the 74°05′N and 73°50′N region, where the direction of the
rift valley changes from the north-northwest in the Knipovich Ridge to the northeast-trending structures of the Mohns Ridge.
It was shown that the tholeiitic magmas of this region shows all the geochemical characteristics of TOR-2, which is typical
of the Mohns Ridge and most oceanic rift zones worldwide, and differ from the basalts of the Knipovich Ridge, which are assigned
to a shallower type of tholeiitic magmatism (Na-TOR). The persistent depletion of the magmas in terms of lithophile element
contents and radiogenic isotope ratios of Sr, Nd, and Pb reflects the conditions of their formation during the ascent of the
depleted oceanic mantle, which has occurred without significant complications since the early stages of the formation of the
Mohns Ridge. 相似文献
8.
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
9.
Comprehensive risk assessments are fundamental to effective emergency management. These assessments need to identify the range
of hazards (or perils) an entity is exposed to and quantify the specific threats associated with each of those hazards. While
hazard identification is commonly, if not formally, conducted in most circumstances, specific threat analysis is often overlooked
for a variety of reasons, one of which is poor communication with subject matter experts. This poor communication is often
attributable to an adherence to scientific jargon and missed opportunities to simplify information. In Canada, for example,
earthquake hazard calculations have been readily available to engineers and scientists for decades. This hazard information,
however, is expressed in terms of peak ground accelerations (PGA) or spectral accelerations (SA) that are foreign concepts
to most emergency managers, community decision-makers and the public-at-large. There is, therefore, a need to more clearly,
simply and effectively express seismic hazard information to the non-scientific community. This paper provides crustal, sub-crustal
and subduction interface earthquake shaking probabilities, expressed as simple percentages for each of 57 locations across
Vancouver Island, British Columbia, Canada. Calculations present the likelihood of earthquake shaking on Vancouver Island
as the probabilities of exceeding each of three shaking intensity thresholds (“widely felt”; onset of “non-structurally damaging”
shaking; and onset of “structurally damaging” shaking) over four timeframes (10, 25, 50 and 100 years). Results are based
on the latest Geological Survey of Canada hazard models used for the 2010 national building code and are presented in both
tabular and graphic formats. This simplified earthquake hazard information is offered to aid local residents, organizations
and governments in understanding and assessing their risk and to encourage and facilitate sound earthquake preparedness funding
decisions. 相似文献
10.
11.
M. V. Mints 《Geotectonics》2011,45(4):267-290
The integral 3D model of the deep structure of the Early Precambrian crust in the East European Craton is based on interpretation
of the 1-EU, 4B, and TATSEIS seismic CDP profiles in Russia and the adjacent territory of Finland (FIRE project). The geological
interpretation of seismic images of the crust is carried out in combination with consideration of geological and geophysical
data on the structure of the Fennoscandian Shield and the basement of the East European platform. The model displays tectonically
delaminated crust with a predominance of low-angle boundaries between the main tectonic units and the complex structure of
the crust-mantle interface, allowing correlation of the deep structure of the Archean Kola, Karelian, and Kursk granite-greenstone
terrane with the Volgo-Uralia granulite-gneiss terrane, as well as the Paleoproterozoic intracontinental collision orogens
(the Lapland-Mid-Russia-South Baltia orogen and the East Voronezh and Ryazan-Saratov orogens) with the Svecofennian accretionary
orogen. The lower crustal “layer” at the base of the Paleoproterozoic orogens and Archean cratons was formed in the Early
Paleoproterozoic as a result of underplating and intraplating by mantle-plume mafic magmas and granulite-facies metamorphism.
The increase in the thickness of this “layer” was related to hummocking of the lower crustal sheets along with reverse and
thrust faulting in the upper crust. The middle crust was distinguished by lower rigidity and affected by ductile deformation.
The crust of the Svecofennian Orogen is composed of tectonic sheets plunging to the northeast and consisting of island-arc,
backarc, and other types of rocks. These sheets are traced in seismic sections to the crust-mantle interface. 相似文献
12.
V. M. Danilov 《Astronomy Reports》2011,55(6):473-486
The kinematics of stars in open-cluster models are investigated. The central regions of these model clusters are fairly “cool,
” leading to gravitational instability in the cluster cores. A temporary virilization is observed in the model clusters, during
which an appreciable fraction of the fluctuation energy of the cluster is temporarily transformed into the kinetic energy
of the peculiar motions of stars. The duration of this stage can reach ∼108 yr. The origins of this temporary virialization of the model clusters are discussed. The instability of the intrinsic fluctuations
of the phase density in the centers of six clusters and model clusters is investigated. Several new regions of unstable phase-density
fluctuations are found, in addition to those already known. The observed and model clusters can move toward a stable equilibrium
state when the density of the cluster core both decreases and increases. The structure of regions of instability of the phase-density
fluctuations in the centers of the six clusters is studied. Resonance curves for the amplitudes of steady-state phase-density
fluctuations in the center of NGC 6705 are constructed. Analysis of the structure of the regions of instability indicates
an appreciable rate of fluctuation-energy loss due to relaxation effects. The instability increments and widths of regions
of instability fall off with increasing distance of the cluster from the Galactic center. An important role in the formation
of regions of instability may be played by resonances between the frequency of the orbital motion of the cluster in the Galaxy
and the frequencies of intrinsic phase-density fluctuations in the centers of the clusters considered. 相似文献
13.
The results of regular instrumental observations over geomagnetic field variations in the zones of influence of tectonic faults
during movement of seismic waves of varied intensity are presented. It has been shown that seismic waves with an amplitude
more than 5–10 μm/s, traveling across the fault zone, always produced geomagnetic field variations. At weaker seismic disturbances,
geomagnetic field variations are of the “glimmer” character, and the relative frequency of appearance of the effect drops
as the seismic wave amplitude decreases. The quantitative dependence between the maximal value of the full vector of variations
in geomagnetic field induction in a fault zone and the amplitude of the seismic disturbance has been found for the first time. 相似文献
14.
Yu. B. Gladenkov 《Stratigraphy and Geological Correlation》2010,18(6):660-673
The problems of zonal stratigraphy of the early 21st century are discussed. The great advances achieved in recent years in
using zones in geological practice are noted. At the same time, attention is drawn to the controversies existing in the interpretation
of the concepts “biostratigraphic zone” and “chronozone,” in the methods of drawing the boundaries of such zones, and in the
assessment of the spatial scale of zones and in the understanding of them as stratigraphic units. 相似文献
15.
A numerical estimation is presented on the effects induced in an existing tunnel by the development of a fault from the deep
bedrock during a seismic event. The spreading of the fault within the alluvial deposit hosting the tunnel, and the consequent
effects on its permanent liner, are studied in static conditions through a series of elastic-plastic, plane strain finite
element analyses. They account for the reduction of the shear strength and stiffness characteristics of the faulting zone
with increasing irreversible strains. Even though the calculations require only “standard”, e.g. peak and residual, material
parameters it is shown that these properties can hardly be obtained for the alluvial deposit at hand. To overcome this drawback
a relatively large scale in-situ tests could be performed and its results could be interpreted through a suitable back analysis.
This would permit characterizing the numerical model to be subsequently adopted for the analysis of the faulting process. 相似文献
16.
Overview of Taiwan Earthquake Loss Estimation System 总被引：2，自引：1，他引：2
The National Science Council (NSC) of Taiwan started the HAZ-Taiwan project in 1998 to promote researches on seismic hazard
analysis, structural damage assessment, and socio-economic loss estimation. The associated application software, “Taiwan Earthquake
Loss Estimation System (TELES)”, integrates various inventory data and analysis modules to fulfill three objectives. First,
it helps to obtain reliable estimates of seismic hazards and losses soon after occurrence of large earthquakes. Second, it
helps to simulate earthquake scenarios and to provide useful estimates for local governments or public services to propose
their seismic disaster mitigation plans. Third, it helps to provide catastrophic risk management tools, such as proposing
the seismic insurance policy for residential buildings. This paper focuses on the development and application of analysis
modules used in early loss estimation system. These modules include assessments of ground motion intensity, soil liquefaction
potential, building damage and casualty. 相似文献
17.
Heat flow and gas hydrates of the Baikal Rift Zone 总被引：3，自引：0，他引：3
A. Y. Golmshtok A. D. Duchkov D. R. Hutchinson S. B. Khanukaev 《International Journal of Earth Sciences》2000,89(2):193-211
Multi-channel seismic studies (MCS), performed during a Russian expedition in 1989 and a joint Russian-American expedition
in 1992, have for the first time revealed a “bottom simulating reflector” (BSR) in Lake Baikal. These data have shown that
gas hydrates occur in the southern and central basins of Lake Baikal in those places where the water depth exceeds 500–700 m.
Four types of tectonic influence on the distribution of the gas hydrate were revealed: (a) Modern faults displace the BSR
as they do with normal seismic boundaries. (b) Older faults displace normal reflectors, whereas the BSR is not displaced.
(c) Modern faults form zones, where the BSR has been totally destroyed. (4) Processes that occur within older fault zones
situated close to the base of the hydrated sediment layer lead to undulations of the BSR. The thickness of the hydrate stability
field (inferred from seismic data) ranges between 35 and 450 m. Heat-flow values determined from BSR data range from 48 to
119 mW/m2. A comparison between heat-flow values from BSR data and values measured directly on the lake bottom shows an overall coincidence.
Changes in water level and bottom-water temperature that occurred in the past have had no noticeable influence on the present
BSR depths or heat-flow values. Determination of deep heat flow from BSR data is in this case more reliable than by direct
measurements.
Received: 10 December 1998 / Accepted: 15 November 1999 相似文献
18.
19.
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
20.
The epicentral tract of the great Assam earthquake of 1897 of magnitude 8·7 was monitored for about 6 months using an array
of portable seismographs. The observed seismicity pattern shows several diversely-oriented linear trends, some of which either
encompass or parallel known geological faults. A vast majority of the recorded micro-earthquakes had estimated focal depths
between 8–14 km. The maximum estimated depth was 45 km. On the basis of a seismic velocity model for the region reported recently
and these depth estimates we suggest that the rupture zone of the great 1897 earthquake had a depth of 11–12 km under the
western half of the Shillong massif. Four composite fault plane solutions define the nature of dislocation in three of the
seismic zones. Three of them show oblique thrusting while one shows pure dip slip reverse faulting. The fault plane solutions
fit into a regional pattern of a belt of earthquakes extending in NW-SE direction across the north eastern corner of the Bengal
basin. The maximum principle stress axis is approximately NS for all the solutions in conformity with the inferred direction
of the Indian-EuroAsian plate convergence in the eastern Himalaya. 相似文献