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Mahendra, R. S.

Consequence of Cyclonic Storm Phailin on Coastal Morphology of Rushikulya Estuary: An Arribada Site of Vulnerable Olive Ridley Sea Turtles along the East Coast of India

The Admissible Tsunamigenic Source Region of 24 September 2013 Land-Based Earthquake - Application of Backward Ray Tracing Technique

Abstract Views :216 | PDF Views:85

Authors

Ch. Patanjali Kumar ¹, B. Ajay Kumar ¹, E. Uma Devi ¹, R. S. Mahendra ¹, M. V. Sunanda ¹, M. Pradeep Kumar ¹, J. Padmanabham ¹, S. Dipankar ¹, T. Srinivasa Kumar ¹

Affiliations
1 Indian National Centre for Ocean Information Services (INCOIS), Hyderabad 500 090, IN

Source

Current Science, Vol 108, No 9 (2015), Pagination: 1712-1716

Abstract

A minor tsunami of about 50 cm was generated along the coast of Qurayat near Makran subduction zone in the Arabian Sea due to the 24 September 2013 Pakistan earthquake of magnitude 7.6 M_w(mB), although its source was ∼200 km far inland of the Makran trench. The real-time sea-level observation network in the Arabian Sea recorded minor tsunami arrivals. In an attempt to explain the mechanism of this unusual tsunami, we use backward ray tracing technique to map the admissible region of tsunamigenic source. Basically, in this technique the ray equations are integrated starting from the specific locations of tsunami observations, in all possible directions. The known travel time of the initial waves to the respective tide gauges and tsunami buoys is used in this method. Backward wave front is constructed by joining all end-points of the rays from each of the locations. The region where the envelope of all backward wave fronts converges is considered as the source of the tsunami, which is ∼470 km from the earthquake epicentre with the location at 24.8 N and 61.5 E. The admissible region identified is an undersea section between Chabahar and Gwadar, where a mud island had appeared subsequent to this earthquake. Convergence of the tsunami source zone and location of the mud island suggest that the sudden uplift must have caused the tsunami.

Keywords

Backward Ray Tracing, Earthquake, Tsunami, Subduction Zone.

Full Text

Differential Bleaching Patterns in Corals of Palk Bay and the Gulf of Mannar

Abstract Views :212 | PDF Views:75

Authors

P. Krishnan ¹, R. Purvaja ¹, C. R. Sreeraj ¹, R. Raghuraman ¹, R. S. Robin ¹, K. R. Abhilash ¹, R. S. Mahendra ², A. Anand ³, M. Gopi ¹, P. C. Mohanty ², K. Venkataraman ¹, R. Ramesh ¹

Affiliations
1 National Centre for Sustainable Coastal Management, Ministry of Environment, Forest and Climate Change, Anna University Campus, Chennai 600 025, IN
2 Indian National Centre for Ocean Information Services, Hyderabad 500 090, IN
3 Regional Remote Sensing Centre, Indian Space Research Organisation, Nagpur 440 010, IN

Source

Current Science, Vol 114, No 03 (2018), Pagination: 679-685

Abstract

The status of reefs in Palk Bay and the Gulf of Mannar was studied during April–May 2016 following a bleach alert, as the sea surface temperature recorded a sudden increase from 30.5°C to 34.0°C in Gulf of Mannar. About 71.48% ± 8.9% of the corals in Palk Bay and 46.04% ± 3.78% in Thoothukkudi group of Islands in Gulf of Mannar were found bleached, showing a clearly decreasing trend from north to south, which could be attributed to the corresponding pattern in intensity of SST recorded in the study sites. Observations of bleaching patterns among different life-forms showed 68% of the bleached corals were massive forms. It was observed that 22 out of the 26 massive forms were bleached, while the Acropora corymbose (ACC), digitate (ACD) and encrusting coral (CE) forms were not bleached in any of the study sites in Palk Bay and Gulf of Mannar. The study suggests that the ACC, ACD and CE forms have adapted to thermal stress, subsequent to the earlier mass bleaching events. The study highlights the need for understanding the molecular mechanism of the association between corals and the symbiotic algae, for further understanding on coral bleaching in Indian waters.

Keywords

Adaptive Coral Bleaching, Gulf of Mannar, Palk Bay.

Full Text

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