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Yogendra Singh Biju John G P Ganapathy Abhilash George S Harisanth K S Divyalakshmi Sreekumari Kesavan 《Journal of Earth System Science》2016,125(4):821-839
The region around Wadakkancheri, Trichur District, Kerala is known for microseismic activity, since 1989. Studies, subsequent to 2nd December 1994 (M =4.3) earthquake, identified a south dipping active fault (Desamangalam Fault) that may have influenced the course of Bharathapuzha River. The ongoing seismicity is concentrated on southeast of Wadakkancheri and the present study concentrated further south of Desamangalam Fault. The present study identifies the northwestern continuity of NW–SE trending Periyar lineament, which appears to have been segmented in the area. To identify the subtle landform modifications induced by ongoing tectonic adjustments, we focused on morphometric analysis. The NW–SE trending lineaments appear to be controlling the sinuosity of smaller rivers in the area, and most of the elongated drainage basins follow the same trend. The anomalies shown in conventional morphometric parameters, used for defining basins, are also closely associated with the NW–SE trending Periyar lineament/s. A number of brittle faults that appear to have been moved are consistent with the present stress regime and these are identified along the NW–SE trending lineaments. The current seismic activities also coincide with the zone of these lineaments as well as at the southeastern end of Periyar lineament. These observations suggest that the NW–SE trending Periyar lineaments/faults may be responding to the present N–S trending compressional stress regime and reflected as the subtle readjustments of the drainage configuration in the area. 相似文献
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Reassessing the earthquake hazard in Kerala based on the historical and current seismicity 总被引:2,自引:0,他引:2
C.P. Rajendran Biju John K. Sreekumari Kusala Rajendran 《Journal of the Geological Society of India》2009,73(6):785-802
Given the lack of proper constraints in understanding earthquake mechanisms in the cratonic interiors and the general absence
of good quality database, here we reassess the seismic hazard in the province of Kerala, a part of the •stable continental
interior•, based on an improved historical and instrumental database. The temporal pattern of the current seismicity suggests
that >60% of the microtremors in Kerala occurs with a time lag after the peak rainfall, indicating that hydroseismicity may
be a plausible model to explain the low-level seismicity in this region. Further, an increment in overall seismicity rate
in the region in the recent years is explained as due to increased anthropogenic activities, which includes changes in hydrological
pathways as a consequence of rapid landscape changes. Our analyses of the historical database eliminate a few events that
are ascribed to this region; this exercise has also led to identification of a few events, not previously noted. The improved
historical database essentially suggests that the central midland region is more prone to seismic activity compared to other
parts of Kerala. This region appears to have generated larger number of significant earthquakes; the most prominent being
the multiple events (doublets) of 1856 and 1953, whose magnitudes are comparable to that of the 2000/2001 (central Kerala)
events. Occurrences of these historical events and the recent earthquakes, and the local geology indicative of pervasive faulting
as shown by widely distributed pseudotachylite veins suggest that the NNW-SSE trending faults in central midland Kerala may
host discrete potentially active sources that may be capable of generating light to moderate size earthquakes. The frequency
of earthquakes in central Kerala evident from the historical database requires that the seismic codes stipulated for this
region are made mandatory. 相似文献
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Jiyoung Lee Jae-Hyun Lim Junhyung Park Seok-Hyun Youn Hyun-Ju Oh Ju-Hyoung Kim Myung Kyum Kim Hyeyoun Cho Joo-Eun Yoon Soyeon Kim Kesavan Markkandan Ki-Tae Park Il-Nam Kim 《Ocean Science Journal》2018,53(2):251-260
Microbial community composition varies based on seasonal dynamics (summer: strongly stratified water column; autumn: weakly stratified water column; winter: vertically homogeneous water column) and vertical distributions (surface, middle, and bottom depths) in the Gadeok Channel, which is the primary passage to exchange waters and materials between the Jinhae-Masan Bay and the South Sea waters. The microbial community composition was analyzed from June to December 2016 using 16S rRNA gene sequencing. The community was dominated by the phyla Proteobacteria (45%), Bacteroidetes (18%), Cyanobacteria (15%), Verrucomicrobia (6%), and Actinobacteria (6%). Alphaproteobacteria (29%) was the most abundant microbial class, followed by Flavobacteria (15%) and Gammaproteobacteria (15%) in all samples. The composition of the microbial communities was found to vary vertically and seasonally. The orders Flavobacteriales and Stramenopiles showed opposing seasonal patterns; Flavobacteriales was more abundant in August and December while Stramenopiles showed high abundance in June and October at all depths. The genus Synechococcus reached extremely high abundance (14%) in the June surface water column, but was much less abundant in December water columns. Clustering analysis showed that there was a difference in the microbial community composition pattern between the strongly stratified season and well-mixed season. These results indicate that the seasonal dynamics of physicochemical and hydrologic conditions throughout the water column are important parameters in shaping the microbial community composition in the Gadeok Channel. 相似文献
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B. Ravindra Prabhu Kesavan K. C. Thulasidharen M. Rajalingam K. Sagayanathan P. U. Kamath Namgyal Dorjey Angchuk Dorjee P. M. M. Kemkar Tsewang Dorjai Ravinder K. Banyal 《Journal of Astrophysics and Astronomy》2018,39(5):60
We report the observations of the solar chromosphere from a newly commissioned solar telescope at the incursion site near Pangong Tso lake in Merak (Leh/Ladakh). This new \(\hbox {H}_{\alpha }\) telescope at the Merak site is identical to the Kodaikanal \(\hbox {H}_{\alpha }\) telescope. The telescope was installed in the month of August 2017 at the Merak site. The telescope consists of a 20-cm doublet lens with additional re-imaging optics. A Lyot filter with 0.5 Å passband isolates the Balmer line of the hydrogen spectra to make the observations of the solar chromosphere. The observations made in \(\hbox {H}_{\alpha }\) wavelength delineates the magnetic field directions at the sunspot and the quiet regions. A CCD detector records the images of the chromosphere with a pixel resolution of 0.27\(^{\prime \prime }\) and covers 9.2\(^{\prime }\) field-of-view. This telescope has a good guiding system that keeps the FoV in the intended position. We report the development of control software for tuning the filter unit, control detector system, observations and calibration of the data to make it useful for the scientific community. Some preliminary results obtained from the Merak \(\hbox {H}_{\alpha }\) telescope are also presented. This high altitude facility is a timely addition to regularly obtain \(\hbox {H}_{\alpha }\) images around the globe. 相似文献
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