Morphometric analysis of the Andaman outer shelf and upper slope——Implications for the recent slope failure events

The devastating 2004 tsunamis that hit the southwestern coast of Thailand pose a serious threat to people along the coastal zone. A major aim for the tsunami hazard prediction is better prediction of the next tsunamis and their impacts. In this paper, we present the first implications of recent slope failure events of the Andaman outer shelf and upper slope based on a new detailed bathymetric data and subbottom profiler records acquired during two cruises of the MASS project in 2006 and 2007. Morphometric analysis reveals a variety of anomalous features,including: three large plateaus surrounded by moats, ruggedness and unevenness of slope morphology, and two translational submarine landslides. Two submarine landslides are studied from the detailed bathymetric data and subbottom profiler record covering the upper slope of the Andaman Sea shelf break within Thai exclusive economic zone. Maximum approximated volumes of both displaced masses are 4.8×10~7 m~3 and 2.2×10~7 m~3.Considering the data, there is no evidence that landslides have been the sources for tsunami hazard potential in recent geological time. These prerequisites will allow better study of slope failure events in the area. Further investigation is required to better understand obvious geotectonic phenomena.

On the Generation and Evolution of Internal Solitary Waves in the Andaman Sea

Internal solitary waves(ISWs)are ubiquitous in the Andaman Sea,as revealed by synthetic aperture radar images;however,their generation mechanisms and corresponding influencing factors remain unknown.Based on a nonhydrostatic two-dimensional model,the generation of ISW packets along the transect of a channel lying between Batti Malv Island and Car Nicobar Island is investigated.Moreover,the influences of topographic characteristics,seasonal stratifications,and tidal forcings are analyzed through a series of sensitivity runs.The simulation results indicate that bidirectional rank-ordered ISW packets are generated by the nonlinear steepening of internal tides.An east-west ISW asymmetry is observed,which is attributed to distinct topographic characteristics.The surrounding sills can also generate internal wave beams,which modulate the intensity of ISWs.However,the topographic structure of the west flank of the ridge mainly contributes to the suppression of westward ISWs,which decreases the modulating effect of internal wave beams.During the spring tide,the generation of ISWs is enhanced.During the neap tide,ISWs are weak,and the east-west ISW asymmetry is less obvious.Moreover,seasonal stratification only has a minor effect on the generation and evolution of ISWs.

Seasonal stress on semen quality profiles, seminal biochemical and oxidative stress attributes in endangered Teressa goat of Andaman and Nicobar Islands

Objective:To measure seasonal effects on semen quality profiles,seminal biochemical and oxidative stress attributes in fresh and liquid stored semen in monsoon and dry seasons.Methods:A total of 10 Teressa bucks(3-4 years)were selected from breeding farm,ICAR-Central Island Agricultural Research Institute,Port Blair,Andaman and Nicobar Islands,India.Semen samples(n=25 per season)were collected through artificial vagina method and preserved at refrigerated temperature(5℃)for 48 h using Tris citrate glucose based extender.We detected semen quality parameters[volume,mass activity,pH,sperm concentration,total motility,viability,total sperm abnormality,and plasma membrane,acrosomal and nuclear integrities],biochemical profiles[aspartate amino transferase(AST),alanine amino transferase(ALT)and total cholesterol],and oxidative stress markers[total antioxidant capacity(TAC)and malondialdehyde(MDA)]during monsoon and dry seasons.Results:Semen quality parameters significantly differed between seasons(P<0.05)and among storage periods(P<0.05).Volume,pH,mass activity,motility,viability,acrosomal,plasma membrane and nuclear integrities,and TAC were significantly higher(P<0.05).Sperm concentration,sperm abnormalities,MDA,AST,ALT and total cholesterol were significantly lower in fresh semen of monsoon than dry season(P<0.05).Motility,viability,acrosomal,plasma membrane and nuclear integrities,and TAC were significantly decreased(P<0.05)while sperm abnormality,AST,ALT,total cholesterol and MDA were significantly increased as liquid semen storage period advanced(P<0.05).Conclusions:Monsoon season has higher beneficial effects on semen quality profiles and liquid stored semen remained usable for upto 48 h.Good quality ejaculates with higher TAC and lower MDA can be cryopreserved and will be used for artificial insemination.

The Probable Cause for Nesting Pattern of Olive Ridley (Lepidochelys olivacea) at Ramnagar Beach, North East Coast of Andaman Island, India

The nesting behaviour of sea turtles remains a subject to study, due to their enigmatic pattern of seasonal breeding activities. Over a period of time, several reports have been made in this context associated with the nesting behaviour of the Olive Ridley turtles. In the present study, characteristics of the breeding beach and nesting pattern of Olive Ridley (Lepidochelys olivacea) at Ramnagar along N-E coast of Andaman Islands were investigated, during the nesting periods 2016-2017. The study area hosts Olive Ridley, the dominant sea turtles with more than 300 individuals nesting each year. For this study, the number of sea turtles visited, nested, the sediment characters, salinity, and temperature were taken. The exposed sandy nesting beach characteristics are prone to varying degrees of morphological changes every day. The results depict that even though similar grain size (Coarse Sand to Fine Sand and Very well sorted to Poorly Sorted), with an ambient incubating temperature, pH and salinity with wide nesting area, the selective nesting in the particular location of the beach identified because of comfortable energy conditions in the waters (1.5 m/s) favours the female turtles to reach the beach at the preferable site of Ramnagar and nest.

Occurrence of <i>Chloeia flava pulchella</i>Baird, 1868, from Off Junglighat, South Andaman, India

Fire-worms from the family Amphinomidae Lamark, 1818, act as a predator, scavenger and sedimentivores, in nearshore waters. This family has 146 valid species among them 18 numbers reported from Indian marine environment and 11 reported from the Andaman waters. Among this family, genus Choleia Lamark. 1818, reported 4 species and 1 subspecies from the Andaman waters. Among these the species Chloeia flava pulchella Baird, 1868was reported by Tampi and Rangarajan, 1964, but no detailed species description was found for this species. During the studies on continuous monitoring of the environmental parameter of nearshore waters of off South Andaman region, a specimen of Chloeia flava pulchella Baird, 1868, was collected. Later the cursory analysis for this specimen identification was revealed that the detailed description of this species found in this region was not available in the literature. So, the detailed taxonomic description was developed and presented in this article.

A study of the spatial-temporal distribution and propagation characteristics of internal waves in the Andaman Sea using MODIS

This paper describes investigations of the internal waves in the Andaman Sea using Moderate Resolution Imaging Spectroradiometer(MODIS)imagery over the period of June 2010 to May 2016.Results of the spatial and temporal distribution,generation sources and propagation characteristics of internal waves are presented.The statistical analysis shows that internal waves can be observed in almost the entire area of the Andaman Sea.Most internal waves are observed in the northern,central and southern regions of the Andaman Sea.A significant number of internal waves between 7°N and 9°N in the East Indian Ocean are also observed.Internal waves can be observed year-round in the Andaman Sea,while most of internal waves are observed between February and April,with a maximum frequency of 15.03%in March.The seasonal distribution of the internal waves shows that the internal waves have mostly been observed in the dry season(February to April),and fewer internal waves are observed in the rainy season(May to October).The double peak distribution for the occurrence frequency of internal waves is found.With respect to the lunar influence,more internal waves are observed after the spring tide,which implies the spring tide may play an important role in internal wave generation in the Andaman Sea.Generation sources of internal waves are explored based on the propagation characteristics of internal waves.The results indicate that six sources are located between the Andaman Islands and the Nicobar Islands,and one is located in the northern Andaman Sea.Four regions with active internal wave phenomenon in the Andaman Sea were presented during the MODIS survey,and the propagation speed of internal waves calculated based on the semidiurnal generation period is smaller than the results acquired from pairs of the images with short time intervals.

Geochemical cycling during subduction initiation:Evidence from serpentinized mantle wedge peridotite in the south Andaman ophiolite suite

The ophiolite suite from south Andaman Islands forms part of the Tethyan Ophiolite Belt and preserves the remnants of an ideal ophiolite sequence comprising a basal serpentinized and tectonised mantle peridotite followed by ultramafic and mafic cumulate units, basaltic dykes and spilitic pillow basalts interlayered with arkosic wacke. Here, we present new major, trace, rare earth(REE) and platinum group(PGE) element data for serpentinized and metasomatized peridotites(dunites) exposed in south Andaman representing the tectonized mantle section of the ophiolite suite. Geochemical features of the studied rocks, marked by Al_2 O_3/TiO_2 > 23, LILE-LREE enrichment, HFSE depletion, and U-shaped chondrite-normalized REE patterns with(La/Sm)N > 1 and(Gd/Yb)N <1, suggest contributions from boninitic mantle melts. These observations substantiate a subduction initiation process ensued by rapid slab roll-back with extension and seafloor spreading in an intraoceanic fore-arc regime. The boninitic composition of the serpentinized peridotites corroborate fluid and melt interaction with mantle manifested in terms of(i) hydration, metasomatism and serpentinization of depleted, MORB-type, sub-arc wedge mantle residual after repeated melt extraction; and(ii) refertilization of refractory mantle peridotite by boninitic melts derived at the initial stage of intraoceanic subduction. Serpentinized and metasomatized mantle dunites in this study record both MOR and intraoceanic arc signatures collectively suggesting suprasubduction zone affinity. The elevated abundances of Pd(4.4-12.2 ppb) with highΣPPGE/∑IPGE(2-3) and Pd/Ir(2-5.5) ratios are in accordance with extensive melt-rock interaction through percolation of boninitic melts enriched in fluid-fluxed LILE-LREE into the depleted mantle after multiple episodes of melt extraction. The high Pd contents with relatively lower Ir concentrations of the samples are analogous to characteristic PGE signatures of boninitic magmas and might have resulted by the infiltration of boninitic melts into the depleted and residual mantle wedge peridotite during fore-arc extension at the initial stage of intraoceanic subduction. The PGE patterns with high Os + Ir(2-8.6 ppb)and Ru(2.8-8.4 ppb) also suggest mantle rejuvenation by infiltration of melts derived by high degree of mantle melting. The trace, REE and PGE data presented in our study collectively reflect heterogeneous mantle compositions and provide insights into ocean-crust-mantle interaction and associated geochemical cycling within a suprasubduction zone regime.

Late Cenozoic seismic stratigraphy of the Andaman Forearc Basin,Indian Ocean

Interpretation of new multichannel seismic reflection data from the Andaman Forearc Basin(AFB) in the northern Indian Ocean is presented here. The highquality multichannel seismic data from the Andaman Forearc region enable us to examine the seismic characters and to demarcate seismic sequences bounded by distinct unconformities. Ages of marked seismic horizons have been calibrated with available litholog data from nearby industry boreholes. Seismic interpretation of new data shows that the AFB is filled with * 4.5-s-two way travel time(TWT) thick Neogene to Recent sediments. The entire basin assemblage exhibits two distinct major sequences pertaining to the Neogene and Quaternary times. A large part of the basin is filled with intermittent mass transport deposits(MTD). We infer that the episodic uplift of the Invisible Bank, protuberance of the outerarc and regular deformation through reactivation of preexisting normal faults since the Pleistocene could be attributed as causal mechanisms for the MTDs. Strong bottom simulating reflectors are identified in the Late Miocene and younger sediments of the outerarc and AFB at a depth of * 0.6 s TWT and correspond to the presence of gas hydrates in this region. Our interpretations have significant implications for geodynamic as well as resource exploration in the AFB.

Study on the propagation velocity of internal solitary waves in the Andaman Sea using Terra/Aqua-MODIS remote sensing images

The Andaman Sea has been a classic study region for internal solitary waves(ISWs)for several decades,and extraordinarily large ISWs are characteristic of the Andaman Sea in the Indian Ocean.This paper presents results on the estimation of the propagation velocity of ISWs in the Andaman Sea that were tracked using 195 image pairs acquired by MODIS National Aeronautics and Space Administration(NASA)Terra/Aqua satellites between January 2014 and December 2018.A total of 562 ISWs were identified during the period,and the results of the propagation velocity distribution of ISWs in the Andaman Sea are presented.The estimated propagation velocity of ISWs agrees well with the theoretical results derived from the Korteweg-de Vries(KdV)equation using monthly climatology stratification data and local bathymetry.The ISW propagation velocity decreases as they propagate from deep to shallow water;the maximum propagation velocity of 3.27 m/s was estimated on the western side of the Nicobar Islands and minimum speed of 0.54 m/s occurred in the shallow water region of the southeastern Andaman Sea.The results show that the ISW propagation characteristics differ in the northern,central,and southern regions of the Andaman Sea.In the northern Andaman Sea,the velocity of ISWs propagating westward was greater than that of ISWs propagating eastward at the same water depth.In the central Andaman Sea,the propagation velocity of the ISWs differed over a small area at a depth of 2500 m,and the velocity of ISWs in the deep mixing layer in winter was higher than that in the shallow mixing layer in spring.Monthly variations in ISW propagation velocity were analyzed in the southern Andaman Sea,and the velocity of ISWs differed greatly in shallow water and was not significantly different in deep water.Water depth and monthly stratification play vital roles in controlling the phase speed of ISWs in the Andaman Sea.This study will provide a basis for the propagation and prediction of ISWs in the Andaman Sea.

GRACE detection of the medium-to far-field coseismic gravity changes caused by the 2004 Mw9.3 Sumatra-Andaman earthquake

Large earthquakes cause observable changes in the Earth’s gravity field, which have been detected by the Gravity Recovery and Climate Experiment (GRACE). Since most previous studies focus on the detection of near-field gravity effects, this study provides the results from the medium- to far-field gravity changes caused by the 2004 Sumatra-Andaman earthquake that are recorded within GRACE monthly solutions. Utilizing a spherical-earth dislocation model we documented that large-scale signals predominate in the global field of the coseismic gravity changes caused by the earthquake. After removing the near-field effects, the coseismic gravity changes show a negative anomaly feature with an average magnitude of -0.18×10-8 m·s-2 in the region ranging ～40° from the epicenter, which is considered as the "medium ffield" in this study. From the GRACE data released by Center for Space Research from August 2002 to December 2008, we retrieved the large-scale gravity changes smoothed with 3 000 km Gaussian ffilter. The results show that the coseismic gravity changes detected by GRACE in the medium field have an average of (-0.20±0.06)×10-8 m·s-2, which agrees with the model prediction. The detection confirms that GRACE is sensitive to large-scale medium-field coseismic gravitational effects of mega earthquakes, and also validates the spherical-earth dislocation model in the medium field from the perspective of satellite gravimetry.

Detection and interpretation of the Earth's free oscillations excited by the great Sumatra-Andaman earthquake with GGP station data

The mode serials of the Earth's free oscillation provide some important information on the Earth's deep structure and superconducting gravimeters (SG) can investigate the phenomena of the Earth's free oscillations with high accuracy. The great Sumatra-Andaman earthquake fully excited the Earth's free oscillations and these signals were perfectly recorded by five superconducting gravimeters in the globe. After the pre-treatment and spectral analysis on the SG observation data, we obtained the experimented mode serials of the Earth's free oscillations consisting of 147 modes with GGP station data. These observed modes were themselves some new important data for the study of the Earth's deep structure. On the basis of the discussions on some checked inner-core-sensitive modes, we distinguished three layers from the inner core, and the boundary of the upper layer was compatible with the formerly known transition zone in the inner core based on seismic body waves and supported that there were the hemispherical variation and very lower shear velocity zone in the lower inner core.

Diseases and compromised health states of massive Porites spp. in the Gulf of Thailand and the Andaman Sea

In this study, we assess coral health by detecting the severity of coral diseases and compromised health states on massive Porites. Field surveys are conducted at twenty-two sites covering the eastern, inner and western Gulf of Thailand as well as the Andaman Sea during 2010–2015. A total of nine coral diseases and signs of compromised health are observed in the waters of Thailand, consisting of pigmentation responses(pink lines, pink patches,pink spots and pink borers), white syndromes(white patches, white bands and ulcerative white spots), growth anomalies, and unusual bleaching patterns. The highest severity of all observed coral diseases and signs of compromised health are found at Ko Khang Khao in the inner Gulf of Thailand, while that observed in the Andaman Sea is relatively low. Composition of the diseases vary across the study sites. Four groups of study sites,in which there is an 80% similarity of diseases or signs of compromised health composition, are clustered and detected based on the Bray-Curtis similarity. The canonical analysis of principal coordinates reveal that most study sites in the Gulf of Thailand, especially the inner Gulf of Thailand, tend to show a high severity of the diseases. The association of disease severity and composition and the level of human impact are also detected.The study sites located near the shores and/or the areas with intensive tourism tend to have higher human impact, especially on poor water quality, which may be linked to the higher severity and composition of coral diseases and signs of compromised health in the Gulf of Thailand. Fish bites are also observed in many study sites.The severity of fish bites in the Gulf of Thailand is much lower compared to the Andaman Sea. Ko Rawi exhibits the highest severity, following by Ko Surin Nua and Ko Butang. The study sites within marine national park boundaries have a significantly higher severity of fish bites than those outside of the marine national park boundaries. This study suggests that higher coral diseases and signs of compromised health severity might be linked to anthropogenic disturbances on coral communities in the waters of Thailand.

Identification of Y-Nauplii (Facetotecta) in Andaman Sea, India

The Facetotecta is among the lesser known groups in the world ocean. The present study recorded two types of Facetotecta in the Andaman Sea, off Andaman Islands. These two types of Facetotecta were observed during the period of August 2015, July 2016 and October 2017 and identified as Type I Hansenocaris corvinae and Type IX Hansenocaris leucadea. However, the cursory analysis suggested that the Type IX is a new type of Facetotecta and named it as Type XII Hansenocaris portblairenae sp. (nov). This finding suggests that this Facetotecta observation is the first report in the Andaman Sea, as well as in the Indian Ocean Region.

Distribution of Gastropods in the Intertidal Environment of South, Middle and North Andaman Islands, India

Andaman and Nicobar Islands, the gastropod diversity is high, due to the majority of shores are rocky. The wet rocky shore promotes algal growth, which is ultimate for feeding ground for gastropod growth and development leading to more diversity. The global warming, anthropogenic activities, industrial and domestic pollution, etc., have accelerated the loss of coastal and marine biodiversity components over the last few decades which has been of great concern. However, except global warming, the other factors were of least concern with reference to Andaman and Nicobar Islands biodiversity due to a pristine environment. Therefore, exploration of biodiversity in these islands is essential to create a baseline data for record and future research. Four locations of south to north Andaman Islands which represented Carbyns Cove from south Andaman, Rangat and Mayabunder from the Middle Andaman and Diglipur from the North Andaman were selected for this study. Gastropoda species were collected for a period of one year in three prevailing seasons of Andaman and Nicobar Islands. They are South West Monsoon (SW monsoon), North East Monsoon (NE Monsoon) and Non Rainy Seasons (NR Seasons). The present study of gastropods distribution in the South, Middle and North Andaman groups of Islands suggested that there are 71 species belonging to 52 genus and 33 families. At any one of the time and any one of the locations, only one occurrence was noticed for 38 species and remaining 33 species were overlapping with respect to stations and seasons. Evaluation of the cluster suggested that Cluster A (NR season in Carbyns Cove) and Cluster B (NE and SW Monsoon in Mayabunder) as a separate entity among the 12 combinations of stations and seasons due to their species representation. It was also concluded that out of 71 studied species, 3 species were not reported till date in these Island environment and 2 species from any other parts of India.

On the heat budget and water mass exchange in the Andaman Sea

The characteristics of the T/S structures,water mass exchange and deep circulation in the Andaman Sea are investigated based on the simulation from a high-resolution general circulation model(MITgcm).The results show that,below 1000 m,the water mass is saltier,warmer and more homogeneous in the Andaman Sea than that in the Bay of Bengal,attributing to the strong vertical mixing at the depth of^1800 m.The water mass exchange between the Andaman Sea and the Bay of Bengal goes through three major channels,which manifests itself as follows:the northern channel(Preparis Channel)is the main passage of water mass transport from the Bay of Bengal to the Andaman Sea,whereas the Middle Channel(the south of Andaman Islands and the north of Nicobar Islands)has an opposite transport;the southern channel(Great Channel)features with a four-layer water exchange which results in the least net transport among the three channels;all the transports through the three channels have an intra-annual variation with a period of half a year.At 1000-m depth,the entire Andaman Sea is occupied by a cyclonic circulation in January and July while by an anticyclonic one in April and October.The semiannual cycle found in both the deep circulation and water mass exchange is likely associated with the downwelling eastward-propagating Kelvin waves induced by the semiannual westerly component in the equatorial Indian Ocean during intermonsoon seasons.

Seasonal and spatial variations of kinematic parameters of internal solitary waves in the Andaman Sea

The horizontally variable density stratification and background currents are taken into the variable-coefficent extended Korteweg-de Vries(evKdV)theory to obtain the geographical and seasonal distribution of kinematic parameters of internal solitary waves in the Andaman Sea(AS).The kinematic parameters include phase speed,dispersion parameter,quadratic and cubic nonlinear parameters.It shows that the phase speed and dispersion parameter are mainly determined by the topographic feature and have limited seasonal variation.The maximum phase speed is 2.6 m/s,which occurs in the cool season(November)in the middle of the AS,while the phase speed in the cool season is slightly larger than those in other seasons,up to 11.4%larger than that in the rainy season(July)in the southern AS.The dispersion parameter in the cool season can be 22.3%larger than that in the hot season.The nonlinear parameters have significant seasonal variation,and they can even change their signs at the continental slope in the north of the AS,from season to season.Meanwhile,the algebraic solitons dominate in the AS with minimum amplitudes(aal)ranging from 0.1 m to 102 m,and the maximum aal occurs in the cool season in the southern AS.The effect of the background flow on the parameters is also studied.The background flow has a great influence on the nonlinear parameters,e.g.,the value of cubic nonlinear parameter can be reduced by 1/3 when the background flow is not considered.

Identification of Groundwater in Hard Rock Terrain Using 2D Electrical Resistivity Tomography Imaging Technique: Securing Water Scarcity at the Time of Seasonal Rainfall Failure, South Andaman

Like many of the tropical islands, the population of Andaman and Nicobar Islands, though not directly, relies predominantly upon rain water harvesting to quench their need and also depends on the groundwater sources. In the background of climate change, severity of hydrological cycle is much anticipated which may cause more extreme and unusual precipitation. It is quite essential to have other alternatives. Accordingly, groundwater could be exploited as a potential alternative. The present study intends to find out the potential groundwater source and estimate aquifer parameters in Kodiyaghat (KD) and Burmanallah (BN). As these areas are composed of very hard rock, Wenner-Schlumberger array has been used to carry out a 2D Electrical Resistivity Tomography survey to find out the fracture zone as well as to delineate the aquifer. KD and BN show maximum resistivity of 25,416 Ωm and 5985 Ωm indicate very hard rock terrain. Similarly, the minimum values of resistivity (21.6 Ωm and 30.4 Ωm) were observed at KD and BN define the presence of freshwater aquifers respectively. The aquifer identified was found to be at a depth of 5 m to 19.9 m at KD and 2.5 m to 20 m at BN. The calculated Hydraulic conductivity (14.85 m/day and 30.14 m/day), transmissivity (86.25 m2/day and 271.27 m2/day) and porosity (28.7% and 31.24%) values at KD and BN confirmed that, the located aquifer was of fresh ground water quality and can be utilized for drinking and house hold purposes. According to the results, almost 70% of the study area is hard rock terrain and 30% comes under potential aquifer zone. The results also show that, both the areas were characterized by Horst and Graben topography and suggest possible groundwater sources for future exploration.

Methodology of Integrated Coastal Zone Management Plan Preparation – Case Study of Andaman Islands, India

Generally, approaches of coastal issues are sectoral basis and solutions have been formed in adhoc fashions which are not long lasting. Integrated Coastal Zone Management (ICZM) is conceived as a holistic management tool working across sectoral, disciplinary, and institutional boundaries. ICZM planning is a continuous process to achieve the goals and objectives by using alternative decisions. ICZM plan is providing boundary conditions for limitation, negotiation and implementation. Planning for coastal management is essentially requires integration of resources, uses, issues, and tools for achieving the management objectives. The ultimate goal of ICZM is to improve the quality of life of human communities. Coastal area management needs integrated, interdisciplinary and multi-sectoral approaches for sustainable utilization of resources, which is the fundamental objective of the resource planners and managers. Methodology for ICZM planning is differing in relation to the regional culture, society, economics, politics, nature, technology, scientific, human behavior, etc. Planning for coastal management is very easy by following the methodology or framework developed for the planning process. A case study of ICZM Plan for Andaman has been prepared by using the participatory methodology, which is the source of consensus for all stakeholders of the Andaman Islands. The tasks of ICZM Plan preparation for Andaman Islands includes, knowledgebase development, selection of ICZM plan preparation methodologies, conflict identification, risk analysis, cost benefit analysis, strategic and action plans, recommendations and institutional changes. This ICZM methodology could be used for comparing and understanding the boundary conditions of union or federal developing nations towards comparative planning.

Wave separation for the great Sumatra-Andaman earthquake with regional seismic array

We analyzed the seismic waveforms from the December 26,2004 Sumatra-Andaman earthquake recorded at broadband seismic stations in western Europe.Previous studies involving of the beam-forming technique and high frequency analysis suggest that the earthquake ruptured with a duration of around 500 s.This very long duration makes P wave overlap with later arrivals such as PP wave,which follows P in about 200 s.Since P waves are crucial for modeling earthquake processes,we propose an iterative method to separate P and PP waveforms.The separated P waveform confirms a second large energy release around 300 s after the initial rupture.The iterative signal separation technique is particularly useful for mixed signals that are not independent and the number of recording stations far exceeds number of mixed signal sources.

A Short Report on Decompression Sickness Incidents in Andaman and Nicobar Islands

Objectives: Due to presence of extensively fascinating coral reef ecosystem in the continental shelf of Andaman and Nicobar Islands, people from all over the world visit these islands of India to indulge in recreational diving. An increased participation figure has also elevated the number of divers at risk for Decompression Sickness (DCS). Despite this, no scientific data are available on DCS incidents from India. Present study is aimed to evaluate the DCS incidents reported in these islands, treatment provided, and the outcome of the treatment. An attempt has also been made to calculate the approximate frequency of DCS in comparison to the participation figure. Methods: Study design is retrospective data analyses of a recompression chamber. Naval Diving Unit Port Blair has the only active decompression chamber available in the islands, and Govind Ballabh Pant Hospital Port Blair was used to collect information on DCS incidents that occurred during the mentioned period. Due to lack of authenticated generalized documents of divers’ health history and dive logs, the scanty information was gathered from the dive centres on the basis of personal interviews/communications among the SCUBA diving instructors. Results: A total of nine cases were reported during the span of last four and half years, and thus approximate frequency of DCS in Andamans was 0.2/10000 divers year. All of the patients recovered completely after receiving the Hyperbaric Oxygen Therapy (HBOT), with no residual symptoms. Conclusions: Incident rate of DCS in Andamans is lower than that in many other parts of the world;possible reason could be under-reporting of less severe DCS cases. During the study period, the number of DCS type II incidents presented for the treatment was higher than that of DCS type I incidents. HBOT proved a complete success in treating DCS cases in the island.