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1.
The storm surge phenomenon in the Arabian Gulf, including the Strait of Hormuz, is discussed with particular emphasis on the development of mathematical models for prediction purposes. The Gulf is mainly influenced by extra-tropical weather systems, whereas the region south of the Strait of Hormuz is affected by tropical cyclones. The west-to-east directed extra-tropical cyclone tracks and the generally east-to-west directed tropical cyclone tracks converge near the Strait of Hormuz. A meso-scale weather system that deserves special attention in prescribing the meteorological forcing functions is the so-called winter Shamal. A two-dimensional numerical model is developed to study the storm surges in the Arabian Gulf. The results show that the Gulf is subject to major negative and positive storm surges. Strong winds associated with the Shamal system, coupled with atmospheric pressure gradients, topography and tidal effects, can give rise to water level deviations of several meters. Storm surges observed during the period 17–19 January 1973 show that negative values in the 0.5 to 1.0m range were widespread in the Gulf. 相似文献
2.
One of the regions of the globe that is frequently and very significantly affected by storm surges is Bangladesh. These high amplitude water-level oscillations are generated by the meteorological forcing fields due to tropical cyclones in the Bay of Bengal. The tide also plays a significant role in determining the time history of the total water level. Due to the greenhouse warming associated with the increasing levels of carbon dioxide in the atmosphere, it is expected that the frequency and intensity of tropical cyclones in the Bay of Bengal will increase substantially within the next 50 to 100 years. This new breed of tropical cyclones, referred to as hypercanes, will generate storm surges on the coast of Bangladesh which could attain amplitudes of up to 15 m, much greater than the present-day amplitudes of up to 6 m. Various mitigation procedures are discussed and compared. 相似文献
3.
Indu Jain P. Chittibabu Neetu Agnihotri S. K. Dube P. C. Sinha A. D. Rao 《Natural Hazards》2006,39(1):71-82
Coastal flooding induced by storm surges associated with tropical cyclones is one of the greatest natural hazards sometimes
even surpassing earthquakes. Although the frequency of tropical cyclones in the Indian seas is not high, the coastal region
of India, Bangladesh and Myanmar suffer most in terms of life and property caused by the surges. Therefore, a location-specific
storm surge prediction model for the coastal regions of Myanmar has been developed to carry out simulations of the 1975 Pathein,
1982 Gwa, 1992 Sandoway and 1994 Sittwe cyclones. The analysis area of the model covers from 8° N to 23° N and 90° E to 100° E.
A uniform grid distance of about 9 km is taken along latitudinal and longitudinal directions. The coastal boundaries in the
model are represented by orthogonal straight line segments. Using this model, numerical experiments are performed to simulate
the storm surge heights associated with past severe cyclonic storms which struck the coastal regions of Myanmar. The model
results are in agreement with the limited available surge estimates and observations. 相似文献
4.
Both finite-element and finite-difference numerical models are applied to simulate storm surges and associated currents generated
by tropical cyclones that struck the coast of Andhra Pradesh, located on the east coast of India. During a cyclone, the total
water level at any location on the coast is made up of the storm surge, surge–wind wave interaction and the tide. The advanced
circulation two-dimensional depth-integrated (ADCIRC-2DDI) model based on finite-element formulation and the two-dimensional
finite-difference model of storm surges developed at IIT Delhi, hereafter referred as IITD storm surge model, are used. These
models are driven by astronomical tides at the open ocean boundary and cyclonic asymmetric winds over the surface of the computational
domain. Comparison of model simulated sea-surface elevations with coarse and finer spatial resolutions suggests that the grid
resolution near the coast is very crucial for accurate determination of the surges in addition to the local bathymetry. The
model underpredicts surges, and the peak surge location shifts more to the right of the landfall as the spatial resolution
of the model becomes coarser. The numerical experiments also demonstrate that the ADCIRC model is robust over the IITD storm
surge model for surge computations as the coastline is better represented in the former. 相似文献
5.
Numerical Modelling of Storm Surge in the Head Bay of Bengal Using Location Specific Model 总被引：1，自引：1，他引：1
The head Bay of Bengal region, which covers part of Orissa and west Bengal in India as well as Bangladesh, is one of the most vulnerable regions of extreme sea levels associated with severe tropical cyclones which cause extensive damage. There has been extensive loss of life and property due to extreme events in this region. Shallow nature of the Bay, presence of Ganga-Brahmaputra-Meghna deltaic system and high tidal range are responsible for storm surges in this region. In view of this a location specific fine resolution numerical modelis developed for the simulation of storm surges. To represent mostof the islands and rivers in this region a 3km grid resolution is adopted. Several numerical experiments are carried out to compute the storm surges using the wind stress forcings representative of 1974, 1985, 1988, 1989, 1991, 1994 and 1999 cyclones, which crossed this region. The model computed surges are in good agreement with the available observations/estimates. 相似文献
6.
Most of the countries around the North Indian Ocean are threatened by storm surges associated with severe tropical cyclones.
The destruction due to the storm surge flooding is a serious concern along the coastal regions of India, Bangladesh, Myanmar,
Pakistan, Sri Lanka, and Oman. Storm surges cause heavy loss of lives and property damage to the coastal structures and losses
of agriculture which lead to annual economic losses in these countries. About 300,000 lives were lost in one of the most severe
cyclones that hit Bangladesh (then East Pakistan) in November 1970. The Andhra Cyclone devastated part of the eastern coast
of India, killing about 10,000 persons in November 1977. More recently, the Chittagong cyclone of April 1991 killed 140,000
people in Bangladesh, and the Orissa coast of India was struck by a severe cyclonic storm in October 1999, killing more than
15,000 people besides enormous loss to the property in the region. These and most of the world’s greatest natural disasters
associated with the tropical cyclones have been directly attributed to storm surges. The main objective of this article is
to highlight the recent developments in storm surge prediction in the Bay of Bengal and the Arabian Sea. 相似文献
7.
Coastal flooding occurs due to storm surges generated by tropical and extra-tropical cyclones on the globe. The meteorological
forcing fields for the generation of storm surges are the tangential surface wind stress on the ocean surface and the normal
atmospheric pressure gradients associated with the weather systems. The large scale forcing from the cyclones is referred
to as the synoptic scale and storm surge prediction from synoptic scale forcing is well developed and is reasonably satisfactory
around the world. However, coastal flooding also occurs from weather systems, with forcing on a meso-scale and also from remote
forcing. It is proposed here that the term “Storm surge” be used to only refer to coastal flooding from synoptic scale forcing
and the terminology “Rissaga” be used for coastal flooding from meso-scale forcing. For flooding due to remote forcing, a
new term “Kallakkadal” is proposed. 相似文献
8.
Neetu Agnihotri P. Chittibabu Indu Jain P. C. Sinha A. D. Rao S. K. Dube 《Natural Hazards》2006,39(1):83-101
The paper describes a two-dimensional bay–river coupled numerical model for storm surges along the Andhra coast of India.
The effect of the Krishna and Godavari rivers on the surge development is analysed. A comparative study of the surge generated
by a tropical cyclone with and without the inclusion of rivers is done in detail. Three cyclones that struck the Andhra coast
in November 1977, May 1990 and November 1996 were used for the simulation studies. It is found that the idealized model without
a river overestimates the sea-level elevation as compared to a more realistic bay–river coupled model. The temporal variation
of surge values at the mouth of the rivers is also studied for all three cyclone cases. It is found that the effect of the
presence of rivers depends on the strength of the cyclone, its point of landfall and the location of the rivers with respect
to the landfall point. 相似文献
9.
P. Chittibabu S. K. Dube J. B. Macnabb T. S. Murty A. D. Rao U. C. Mohanty P. C. Sinha 《Natural Hazards》2004,31(2):455-485
Storm surges generated by the strong tangential wind stressesand normal atmospheric pressure gradients at the sea surface due to tropical cyclones (TC'S)have been studied with the goal of detecting any significant and systematic changes due to climatechange. Cyclone and storm surge data for the 19th and 20th centuries for the Bay of Bengalcoast of the state of Orissa in India are available to varying degrees of quality and detail,the data being more scientific since the advent of the India Meteorological Department in 1875.Based on more precise data for the period 1971 to 2000, statistical projections have been madeon the probable intensities of tropical cyclones for various return periods. The super cyclone ofOctober 29, 1999 (SC1999) appears to have a return period of about 50 years. The cyclones of1831, 1885 and possibly the one in 1895 could have been super cyclones. During the 19th century,there were 72 flooding events associated with cyclones, whereas in the 20th century therewere only 56 events. There was no observational evidence to suggest that there was an increaseeither in the frequency or intensity of cyclones or storm surges on the coast of Orissa. However,the impact of cyclones and surges is on the increase due to increase of population and coastalinfrastructure. 相似文献
10.
A nested model for the simulation of tides and storm surges in the Bohai Sea, China, has been developed based on the three-dimensional finite-volume coastal ocean model. The larger domain covers the entire Yellow Sea and Bohai Sea with a horizontal resolution of ~10 km, and the smaller domain focuses on the Bohai Sea with a fine resolution up to ~300 m. For the four representative storm surges caused by extratropical storms and typhoons, the simulated surge heights are in good agreement with observations at coastal tide gauges. A series of sensitivity experiments are carried out to assess the influence of coastline change due to land reclamation in recent decades on water levels during storm surges. Simulation results suggest that changes in coastline cause changes in the amplitude and phase of the tidal elevation, and fluctuations of surge height after the peak stage of the storm surges. Hence, for the assessment of the influence of coastline changes on the total water level during storm surges, the amplitudes and phases of both the tidal and surge heights need to be taken into account. For the three major ports in the Bohai Bay, model results suggest that land reclamation has created a coastline structure that favors increasing the maximum water level by 0.1–0.2 m. Considering that during the storm surges the total water level is close to or even exceeds the warning level for these ports, further increasing the maximum water level by 0.1–0.2 m has the potential to cause severe damages and losses in these ports.
相似文献11.
Summary
Seismoacoustic Activity in a Coal Seam in Relevance to Destressing. Analysis of the seismoacoustic data obtained in the coal seam Johann Präsident [482] of the mine Friedrich der Große of Ruhr area has been carried out with emphasis on the influence of destressing. The parameters studied are the source distribution pattern, seismic propagation velocity and particle velocity (energy released). Marked changes in these three parameters due to destressing are noticed. The results show that most of the sources of the seismoacoustic events lie within 40 m ahead of the working face with their distribution pattern revealing zones of stress concentration. Accumulation and relief of excessive stress have affected the seismic propagation velocity by +5% and –10% respectively. Particle velocity is also significantly reduced due to destressing.
On leave of absence from the National Geophysical Research Institute, Hyderabad, India.
With 6 Figures 相似文献
Zusammenfassung Seismoakustische Aktivität in einem Kohleflöz in Abhängigkeit von Entspannungsmanahmen. Die seismoakustische Aktivität im Flöz Johann Präsident, Streb 482, auf der Zeche Friedrich der Große (Ruhr-Gebiet) wird unter Berücksichtigung der Einflüsse der Entspannungsmaßnahmen analysiert. Die Verteilung der Herde der seismoakustischen Ereignisse, die seismiche Ausbreitungsgeschwindigkeit und die Schwinggeschwindigkeit bzw. die freiwerdende Energie werden untersucht. Die Entspannungsmaßnahmen haben einen deutlichen Einfluß auf diese drei Parameter. Die Ergebnisse zeigen, daß die meisten seismoakustischen Herde innerhalb von 40 m vor der Strebfront liegen, und ihre Muster der Verteilung Hinweise auf Zonen hoher Druckkonzentration angeben. Es wird eine Schwankung der seismischen Ausbreitungsgeschwindigkeit bis zu +5% bei erhöhtem Druck und –10% während der Entspannungsmaßnahmen beobachtet. Auch die Schwinggeschwindigkeit wird durch die Entspannungsmaßnahmen stark reduziert.
Résumé L'activité sismoacoustique dans une couche de charbon en dépendance des opérations de détente. L'activité sismoacoustique dans la couche Johann Präsident, 482 de la houillère Friedrich der Große (Ruhr-Région) est analysé en considération de l'influence des opérations de détente. La répartition des foyers d'événement sismoacoustique, la vitesse des ondes sismiques et la vitesse du mouvement de particule, c'est-à-dire l'énergie libérée, sont vérifiés. Les opérations de détente ont une influence nette sur ces trois paramètres. Les resultats montrent, que la plupart des foyers d'événement sismoacoustique sont déterminés dans les 40 mètres avant la taille en activité et que leurs structures de répartition permettent des conclusions quant à la concentration de la pression élévée. La variation de la vitesse des ondes sismiques est jusqu'à +5% pendant pression élévée et –10% au cours des opérations de détente. La vitesse du mouvement de particule est aussi très reduite.
On leave of absence from the National Geophysical Research Institute, Hyderabad, India.
With 6 Figures 相似文献
12.
Comparison between two types of multifractal modeling 总被引：1，自引：0，他引：1
The interrelationships between two previously developed multifractal models are discussed. These are the Evertsz-Mandelbrot model developed on the basis of the multifractal spectrum f(), and the Schertzer-Lovejoy model based on the codimension function C() where and represent Hölder exponent and field order, respectively. It is shown how these two models are interrelated: they are identical for values of within the range D–(0)D–min. where D is the Euclidean dimension. For D–maxD–(0), however, f() remains a continuous function of whereas C() assumes constant value. In this respect, the fractal spectrum f() can provide more information about the multifractal measure than the codimension function C(). The properties of the two models are illustrated by application to the binomial multiplicative cascade model. 相似文献
13.
The measurement and recording of the height and spatial extent reached by coastal storm surges is fundamental to scientific progress in understanding these phenomena. Such information is required for better prediction and for risk assessment. Model-based evaluation of increasing delta vulnerability, for example, cannot be tested without long-term, consistent, and sustained observation of actual events. Also, storm surges occur within the temporal context of tidal variation, which must first be characterized through observation. Present standard approaches for measuring storm surges are not optimum. Thus, tidal gauges provide information at one point, whereas the heights reached by surges vary spatially. Also, post-surge ground surveys are expensive, laborious, and commonly lack comparison to similar data obtained for previous surges or for high tides. The advent of moderate spatial resolution, high temporal resolution remote sensing initiated by the launch of the two NASA MODIS sensors greatly reduces these constraints. For over a decade, daily coverage of most coastal land areas, though restricted by cloud cover, has systematically captured the maximum extents reached by both high tides and by storm surges. Automated water classification algorithms are now transforming the incoming image data into GIS water boundary files, again at daily or near-daily time steps. This paper provides a retrospective view of sample storm surges as mapped via these sensors and describes: (a) the present, MODIS-based surface water surveillance system, (b) the mapping enhancement to be provided by frequent-repeat, wide-swath satellite radar imaging, and (c) the emerging prospects for routine global surveillance of storm surge events. Such will be necessary if long-term trends are to be recognized, characterized, and understood, along coastal zones now being affected by both increasing subsidence and rising sea level. 相似文献
14.
A method for estimating earthquake occurrence probability using first- and multiple-order Markov chain models 总被引：1，自引：1，他引：0
Yukio Fujinawa 《Natural Hazards》1991,4(1):7-22
It is valuable in earthquake prediction to determine the occurrence probability of major earthquakes by making use of data obtained from precursory phenomena up to the time of the evaluation. In this study, the time evolution of the state determined by earthquakes and precursory phenomena was modelled using Markov chains. Various probabilities suitable for earthquake prediction were derived from the transition probability of the Markov chain with a chosen length of memory time. As an example, earthquake sequence records for northern China, which covered a period of about two thousand years, were examined and the results were also obtained from modern scientific observations of the radon anomaly which covered a period of about 10 years.Assuming moderate-sized earthquakes of two magnitude ranges 4 3/4 M 5 3/4, 6 M 6 3/4 as precursors to large earthquakes of a magnitude range, 7 M 8 1/2, transition probabilities were calculated for a time interval from 2 to 40 yr. The results showed that the precursory time of moderate-sized earthquakes is mainly distributed in a time span of around several years and that the earthquake occurrence probability is considerably large when the precursory earthquakes occur successively. Furthermore, it was shown that a larger moderate-sized earthquake (4 3/4 M 5 3/4) is a more effective precursor than an entire moderate-sized earthquake (4 3/4 M 6 3/4).Second, a multiple precursor case was tried by means of simulation based on the radon anomaly data obtained during a limited observation period. Simultaneous occurrence of two precursors makes the earthquake occurrence probability increase by 1.5–2.0 for a reasonable choice of a mean recurrence interval of the radon anomaly compared with the case where only a moderate-sized earthquake was treated as the precursor. However, the probability is much the same if the average recurrence interval of the radon anomaly is the same through time, including the preparatory period before the earthquake. 相似文献
15.
The Miocene-Oligocene volcanism of this region is part of the larger Tertiary volcanic province found throughout E. Australia. Within the S.E. Queensland region, the volcanism is strongly bimodal, and has emanated from six major centres, and many additional smaller centres. The mafic lavas (volumetrically dominant) range continuously from ne-normative through to Q-normative and are predominantly andesine-normative; Mg/Mg+Fe (atomic ratios range from 30–60; K2O ranges from 0.42–2.93%, and TiO2 from 0.81–3.6%.Phenocryst contents are low (averaging 6.7 vol.%), and comprise olivine (Fa18–75; Cr-spinel inclusions occur locally in Mg-rich phenocrysts), plagioclase (An25–68), and less commonly augite, which is relatively aluminous in lavas of the Springsure volcanic centre. Very rare aluminous bronzite occurs in certain Q-normative lavas. Groundmass minerals comprise augite, olivine (Fa33–77), feldspar (ranging from labradorite through to anorthoclase and sanidine), Fe-Ti oxides, and apatite. Within many of the Q-normative lavas, extensive development of subcalcic and pigeonitic pyroxenes occurs, and also relatively rarely orthopyroxene. Mineralogically, the ne- and ol-normative lavas, and some of the Q-normative lavas are indistinguishable, and in view of the gradations in chemistry, the term hawaiite has been extended to cover these lavas. The term tholeiitic andesite is used to describe the Q-normative lavas containing Ca-poor pyroxenes as groundmass phases.Megacrysts of aluminous augite, aluminous bronzite, olivine, ilmenite, and spinel sporadically occur within the lavas, and their compositions clearly indicate that they are not derived from the Upper Mantle. Rare lherzolite xenoliths are also found.The petrogenesis of these mafic lavas is approached by application of the thermodynamic equilibration technique of Carmichael et al. (1977), utilizing three parental mineral assemblages that could have been in equilibrium with the magmas at P and T. The models are: (a) standard upper mantle mineralogy; (b) an Fe-enriched upper mantle model (Wilkinson and Binns 1977); (c) lower crust mineralogy, based on analysed megacryst compositions. The calculations suggest that these mafic magmas were not in equilibrium with either mantle model prior to eruption, but show much closer approaches to equilibrium with the lower crust model. Calculated equilibration temperatures and pressures (for the lower crust model) range from 995°–l,391° C (average 1,192), and 7.2–16.3 kb (average 12.4). These results are interpreted in terms of a model of intrusion and magma fractionation within the crust-mantle interface region, with consequent crustal underplating and thickening beneath the Tertiary volcanic regions. Some support for the latter is provided by regional isostatic gravity anomalies and physiographic considerations. 相似文献
16.
In this paper, the main meteorological and meteorologically induced marine disasters in Shanghai are climatologically investigated on the basis of historical qualitative documentary records and quantitative data. Statistics show that disasters may be classified into six different kinds, of which three are fundamental, i.e. floods, winds, and storm surges. Emphasis is placed on the detailed analysis and discussion of floods, tropical cyclones, and Mei-yu which affect Shanghai and cause destructive calamities.Firstly, the classification of floods, their frequencies, and geographical distribution characteristics are described and the regulation of the climatic variation of floods is revealed. Secondly, the frequency, source regions, seasonal variations, tracks, and translatory speeds of tropical cyclones affecting Shanghai, and their induced strong winds, storm rainfalls, and storm surges are systematically studied. Many meaningful conclusions have been reached for providing the climatological background of Shanghai.The climatic change and its regulation of these main disasters in Shanghai have been basically clarified throughout this study. 相似文献
17.
Dr. Jörn H. Kruhl 《International Journal of Earth Sciences》1984,73(2):735-751
Pelites, carbonate-silicate rocks and mafic rocks occurring at the base of the Helgeland nappe complex northwest of Grong (N. Norway) were subjected together with the crystalline basement to medium grade metamorphism and threefold deformation during Caledonian times.During the first act of deformation temperature increased and reached a maximum of 600–650°C at 6–7 Kb after the cessation of the first deformation event. At the peak of metamorphism granitic, aplitic and pegmatitic rocks were formed.During the second and third acts of deformation the temperature decreased to 500–400°C. Mylonites, formed during the second act of deformation, indicate that there was nappe movement from NW to SE. Simple shearing with direction of the main elongation parallel to the fold axes was associated with the second deformation. During the third deformation simple shearing also occurred. However, elongation took place oblique to the fold axes and the sense of rotation was opposite to that of the second deformation.
Zusammenfassung An der Basis des Helgeland-Komplexes nordwestlich von Grong (Nord-Norwegen) wurden pelitische, kalksilikatische und basische Gesteine zusammen mit dem Kristallinen Grundgebirge in kaledonischer Zeit von drei aufeinanderfolgenden Faltungsakten erfaßt. Dabei herrschten amphibolitfazielle Temperaturen.Während der ersten Deformation stieg die Temperatur an. Das Maximum von 600–650°C wurde, bei einem Druck von 6–7 Kb, nach der ersten und vor der zweiten Deformation erreicht. Gleichzeitig intrudierten Granite, Aplite und Pegmatite. Während der zweiten und dritten Deformation sank die Temperatur wieder auf 500–400°C. Im Zuge des zweiten Deformationsaktes entstanden stellenweise Mylonite, die auf Deckenbewegungen von NW nach SE hindeuten. Zweite und dritte Deformation sind beide rotational, während der zweiten liegt die Hauptdehnungsrichtung parallel zu den Faltenachsen, während der dritten aber schräg zu ihnen. Der Rotationssinn der dritten Deformation ist dem der zweiten entgegengesetzt.
Résumé En Norvège septentrionale, au NW de Grong, la base du complexe d'Helgeland composée de metapélites, de roches calc-silicatiques et de roches mafiques, et le soubassement cristallin de ce complexe ont subi ensemble trois actes de déformation successifs à des températures du faciès amphibolites, pendant les temps calédoniens.Durant le premier acte la température a monté. Le maximum de 600–650° C, sous une pression de 6–7 kbar, a été atteint après la fin de cette déformation et avant la deuxième; des roches granitiques, aplitiques et pegmatitiques se sont formées au cours de ce stade. Durant le deuxième et le troisième acte de déformation, la température diminuait à 500–400° C. Des mylonites, indiquant un transport des nappes du NW vers le SE, ont été formées au cours de la deuxième phase. Celle-ci est caractérisée par un mouvement rotatoire par cisaillement simple, l'élongation étant parallèle aux axes des plis. La troisième phase était égalément une phase de mouvements rotatoires, mais en sens opposé et avec un élongation oblique aux axes.
( ) , - - , . . . 600– 650° 6 – 7 , . , . 500 – 400°. , . , , — . , .相似文献
18.
A modeling study of coastal inundation induced by storm surge,sea-level rise,and subsidence in the Gulf of Mexico 总被引：2，自引：2，他引：0
Zhaoqing Yang Taiping Wang Ruby Leung Kathy Hibbard Tony Janetos Ian Kraucunas Jennie Rice Benjamin Preston Tom Wilbanks 《Natural Hazards》2014,71(3):1771-1794
The northern coasts of the Gulf of Mexico (GoM) are highly vulnerable to the direct threats of climate change, such as hurricane-induced storm surge, and such risks are exacerbated by land subsidence and global sea-level rise. This paper presents an application of a coastal storm surge model to study the coastal inundation process induced by tide and storm surge, and its response to the effects of land subsidence and sea-level rise in the northern Gulf coast. The unstructured-grid finite-volume coastal ocean model was used to simulate tides and hurricane-induced storm surges in the GoM. Simulated distributions of co-amplitude and co-phase lines for semi-diurnal and diurnal tides are in good agreement with previous modeling studies. The storm surges induced by four historical hurricanes (Rita, Katrina, Ivan, and Dolly) were simulated and compared to observed water levels at National Oceanic and Atmospheric Administration tide stations. Effects of coastal subsidence and future global sea-level rise on coastal inundation in the Louisiana coast were evaluated using a “change of inundation depth” parameter through sensitivity simulations that were based on a projected future subsidence scenario and 1-m global sea-level rise by the end of the century. Model results suggested that hurricane-induced storm surge height and coastal inundation could be exacerbated by future global sea-level rise and subsidence, and that responses of storm surge and coastal inundation to the effects of sea-level rise and subsidence are highly nonlinear and vary on temporal and spatial scales. 相似文献
19.
R. L. Torres-Roldan 《International Journal of Earth Sciences》1978,67(1):342-355
Generalized development of calc-silicate bands in several alpujarride units of the central and western segments of the Betic Zone, is interpreted as the result of metamorphic differentiation from original calcium-rich sedimentary beds in the sequence. Presence of Scapolite suggests that this phenomenon may have been made possible by the catalizing action of high anion concentrations in the pore fluid medium during metamorphism, probably caused by the existence of evaporic material in the original sediments. This hypothesis, which is further supported by anomalous high Ca, Na and K contents of the enclosing metapelites, leads to the correlation of the present calc-silicate bearing metamorphic formations with well-known permo-werfenian evaporitic series in other units of the Betic Zone. The use of this new criterion of stratigraphic correlation would indicate that highly metamorphosed permo-triassic sequences have often been misidentified as more ancient formations, thus causing an underestimation of the importance of alpine HT-LP metamorphism in the alpujarride tectonic domain.
Zusammenfassung Das häufige Auftreten von Kalksilikatbändern (manchmal mit Skapolith) in einigen alpujarriden Einheiten, besonders im zentralen und westlichen Abschnitt der betischen Kordillere, wird erklärt als Ergebnis einer metamorphen Differentiation von ursprünglich Ca-reichen Schichten. Die Anwesenheit von Skapolith legt eine hohe Anionenkonzentration der intergranularen fluiden Phasen während der Metamorphose nahe, bedingt durch evaporitisches Material der ursprünglichen Sedimente. Diese Hypothese, zusätzlich gestützt durch den extrem hohen Gehalt der umgebenden Pelite an löslichen Kathionen (Ca, Na, K), erlaubt die Korrelation der Kalksilikatbänder-haltigen Formationen mit aus anderen betischen Einheiten bekannten evaporitischen Serien des Permowerfenïan. Auf die stratigraphische Korrelation angewendet, legt dies nahe, daß öfters hochmetamorphe, permotriadische Serien fälschlicherweise als älter betrachtet wurden, was zu einer Unterschätzung der alpinen Metamorphose (Niederdruck-Hochtemperatur) im alpujarridem Bereich führte.
Resumen El desarrollo bastante generalizado de bandas de silicatos calcicos, entre los cuales se encuentra a veces una escapolita, en varias unidades alpujárrides de los segmentos central y occidental de la Zona Bética, es interpretado como el resultado de un proceso de diferenciación metamórfica a partir de lechos sedimentarios originalmente ricos en calcio. La presencia de escapolita sugiere que este hecho ha sido probablemente posible gracias a la existencia de una alta concentración de aniones en el fluido metamórfico intergranular, condicionada por la existencia de material evaporitico en los sedimentos originales. Esta última hipótesis que es ulteriormente apoyada por un contenido anómalamente alto de cationes solubles (Ca, Na, K) en las metapelitas encajantes, permite correlacionar las formaciones que contienen los lechos de silicatos calcicos con conocidas series evaporiticas de edad permowerfenense en otras unidades de la Zona Bética. La aplicación de este nuevo criterio de correlación estratigráfica sugiere que series permotriásicas altamente metamorfizadas han sido a menudo erróneamente interpretadas como más antiguas, hecho que ha conllevado a una substimación de la importancia del metamorfismo (BP-AT) alpino en el dominio tectónico alpujárride.
Résumé Le developpement très fréquent de roches litées à silicates calciques dans quelques unités alpujarrides des regions centrale et occidentale de la Zone Bétique, est interpreté comme la conséquence d'un processus de différenciation métamorphique à partir de lits riches en calcium dans les sequences sédimentaires originelles. La présence de scapolite suggére que ce phénomène a été rendu possible par l'intervention d'un cataliseur naturel, tel que des hautes concentrations en anions dans le milieu fluide intergranulaire pendant le métamorphisme, occasionées probablement par l'existence de materiel évaporitique dans les sédiments originels.Cette hypothese, qui se trouve additionellement supportée par des teneurs élevées en cations solubles des métapelites encaissantes, permet d'assimiler les formations qui contiennent les lits à silicates calciques avec des séries évaporitiques permowerféniennes, bien connues dans d'autres unités des zones internes des Cordilléres Bétiques. L'application de ce nouveau critère de corrélation stratigraphique indiquerait que des séquences permotriasiques fortement affectées par le métamorphisme ont été souvent à tort interprétées comme plus anciennes, amenant ainsi a une sous-estimation de l'importance du métamorphisme alpin (BP-HT) dans le domaine tectonique alpujarride.
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20.
A. D. Rao P. L. N. Murty Indu Jain R. S. Kankara S. K. Dube T. S. Murty 《Natural Hazards》2013,66(3):1431-1441
The devastation due to storm surge flooding caused by extreme wind waves generated by the cyclones is a severe apprehension along the coastal regions of India. In order to coexist with nature’s destructive forces in any vulnerable coastal areas, numerical ocean models are considered today as an essential tool to predict the sea level rise and associated inland extent of flooding that could be generated by a cyclonic storm crossing any coastal stretch. For this purpose, the advanced 2D depth-integrated (ADCIRC-2DDI) circulation model based on finite-element formulation is configured for the simulation of surges and water levels along the east coast of India. The model is integrated using wind stress forcing, representative of 1989, 1996, and 2000 cyclones, which crossed different parts of the east coast of India. Using the long-term inventory of cyclone database, synthesized tracks are deduced for vulnerable coastal districts of Tamil Nadu. Return periods are also computed for the intensity and frequency of cyclones for each coastal district. Considering the importance of Kalpakkam region, extreme water levels are computed based on a 50-year return period data, for the generation of storm surges, induced water levels, and extent of inland inundation. Based on experimental evidence, it is advocated that this region could be inundated/affected by a storm with a threshold pressure drop of 66 hpa. Also it is noticed that the horizontal extent of inland inundation ranges between 1 and 1.5 km associated with the peak surge. Another severe cyclonic storm in Tamil Nadu (November 2000 cyclone), which made landfall approximately 20 km south of Cuddalore, has been chosen to simulate surges and water levels. Two severe cyclonic storms that hit Andhra coast during 1989 and 1996, which made landfall near Kavali and Kakinada, respectively, are also considered and computed run-up heights and associated water levels. The simulations exhibit a good agreement with available observations from the different sources on storm surges and associated inundation caused by these respective storms. It is believed that this study would help the coastal authorities to develop a short- and long-term disaster management, mitigation plan, and emergency response in the event of storm surge flooding. 相似文献