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961.
S. K. Singh J. F. Pacheco M. Ordaz R. S. Dattatrayam G. Suresh P. R. Baidya 《Natural Hazards》2012,64(2):1491-1510
In this paper, we report that the ratio of broadband energy (0.01?C2?Hz) to high-frequency energy (0.3?C2?Hz), E r, estimated from regional seismograms of India, might be a useful parameter in estimating tsunami potential of earthquakes in the Sumatra?CAndaman region. E r is expected to be sensitive to the depth as well as to the source characteristics of an earthquake. Since a shallow and slow earthquake has a greater tsunamigenic potential, E r may be a useful diagnostic parameter. We base our analysis on broadband seismograms of the great earthquakes of Sumatra?CAndaman (2004, M w?~?9.2) and Nias (2005, M w 8.6), 41 of their aftershocks, and the earthquakes of north Sumatra (2010, M w 7.8) and Nicobar (2010, M w 7.4) recorded at VISK, a station located on the east coast of India. In the analysis, we also included the two recent, great strike-slip earthquakes of north Sumatra (2012, M w 8.6, 8.2) recorded at VISK and three south Sumatra earthquakes (2007, M w 8.5; 2007, M w 7.9; 2010, M w 7.8) recorded at PALK, a station in Sri Lanka. We find that E r is a function of depth; shallower earthquakes have higher E r values than the deeper ones. Thus, E r may be indicative of tsunamigenic potential of an earthquake. As M w and E r increase so does the tsunami potential. In addition to the parameter E r, the radiated seismic energy, E s, may be estimated from the regional seismograms in India using empirical Green??s function technique. The technique yields reliable E s for the great Sumatra and Nias earthquakes. E r and E s computed from VISK data, along with M w and focal mechanism, may be useful in estimating tsunami potential along the east coast of India from earthquakes in the Sumatra?CAndaman region in less than ~20?min. 相似文献
962.
Sudhir Kumar Tewatia Asuri Sridharan Mangu Singh Sunanda Rath 《Geotechnical and Geological Engineering》2012,30(4):1037-1043
Degree of consolidation, U, is defined in two ways: (1) by settlement analysis and (2) by dissipation of pore pressure. Equations of vertical and radial consolidations are derived by equating the above two U. The new equations are compared with the existing equations of vertical and radial consolidations. It is shown that new equation of radial consolidation is exactly same as Barron’s equation of equal strain radial consolidation while in case of vertical consolidation it is similar to later part of Terzaghi’s equation of vertical consolidation. A few possible reasons and advantages of comparison are given. The theory of rapid loading methods is based on the equality of these two degrees of consolidations. It is concluded that in rapid loading methods the next load increment can be applied at any time in radial consolidation once the effects of initial compression are over. However, in vertical consolidation it can be applied only after 60% consolidation. 相似文献
963.
This study examines benthic foraminifera (>63 μm) both qualitatively and quantitatively, from 19 closely spaced surficial sediment samples covering 30 to 200 m water depths across the shelf and upper continental slope off north Kerala (SW India). A total of 59 species are recorded. The major constituents of benthic foraminiferal assemblages in the study area are fursenkoinids, bolivinids, nonionids, rotaliids, elphidiids, buliminids, miliolids, gavilinellids, amphestiginids, bagginids, vaginulinids, uvigerinids and various agglutinated taxa. Cluster analysis using Bray Curtis similarity index defines four sample groups, each typified by a characteristic assemblage representing a biofacies. The major benthic foraminiferal biofacies identified are: Biofacies I, Fursenkoina-Nonion-Ammonia beccarii s.l. (30–40 m); Biofacies II, Fursenkoina-Nonion (40–55 m); Biofacies III, Bolivina robusta-Hanzawaia-Cancris-Amphistegina and miliolids (55–115 m) and Biofacies IV, Bolivina persiensis-Uvigerina-Bulimina-Fursenkoina and agglutinants (115–200 m). Relict foraminifera, most commonly represented by shallow-water benthic taxa are concentrated on the outer shelf. The relict assemblage appears to be a product of late Pleistocene low sea level. The foraminiferal biofacies have a good correspondence with the bathymetrically distributed three major lithofacies across the shelf and the upper continental slope. We studied the distribution pattern of individual taxa constituting the biofacies. The study demonstrates a relationship between the pattern of distribution of major benthic fauna and the sediment-size and organic carbon content across the inner shelf to upper slope. Additionally, certain taxa appear to be sensitive to various hydrographic parameters, such as, Bulimina marginata to temperature and Fursenkoina complanata and Uvigerina ex gr. U. semiornata to dissolved oxygen level. 相似文献
964.
We report here, a fossil palm leaf from Lower Siwalik sediments, tied to nearby palaeomagnetically dated 11.2 Ma old beds
exposed in the Baner Khad, near Ranital, Himachal Pradesh. The palm fossil leaf impression has been placed in the genus Palmacites sp. (Family: Arecaceae) based on its diagnostic features such as large palmate leaf without hastula and costa (midrib), showing
coriaceous texture, leaflets diverging from the base of the lamina with prominent midrib and parallel venation. This finding
may indicate presence of tropical to subtropical climatic conditions in the Himalayan foothills around Kangra Valley in the
Middle Miocene time. 相似文献
965.
The existence of gas-hydrates in marine sediments increases the seismic velocity, whereas even a small amount of underlying
free-gas reduces the velocity considerably. The change in velocities against the background (without gas-hydrates and free-gas)
velocity can be used for identification and assessment of gas-hydrates. Traveltime inversion of identifiable reflections from
large offset multi channel seismic (MCS) experiment is an effective method to derive the 2-D velocity structure in an area.
We apply this method along a seismic line in the Kerala-Konkan (KK) offshore basin for delineating the gas-hydrates and free-gas
bearing sediments across a bottom simulating reflector (BSR). The result reveals a four layer 2-D shallow velocity model with
the topmost sedimentary layer having velocity of 1,680–1,740 m/s and thickness of 140–190 m. The velocity of the second layer
of uniform thickness (110 m) varies from 1,890 to 1,950 m/s. The third layer, exhibiting higher velocity of 2,100–2,180 m/s,
is interpreted as the gas-hydrates bearing sediment, the thickness of which is estimated as 100 to 150 m. The underlying sedimentary
layer shows a reduction in seismic velocity between 1,620 to 1,720 m/s. This low-velocity layer with 160–200 m thickness may
be due to the presence of free-gas below the gas-hydrates layer. 相似文献
966.
Ola Ahlqvist Francis Harvey Hyowon Ban Wei Chen Shaun Fontanella Meng Guo Nisheet Singh 《GeoJournal》2013,78(1):61-68
Web 2.0 services and social networking offer possibilities to transform academic publishing to facilitate scientific dialogue. We present ‘The Live Paper’ in this editorial as a concept to consider how to leverage existing web technologies to produce rich, omnidirectional, and interactive narratives on research. Following the format of a traditional research report we describe and discuss how to enrich research reports utilizing various types of analytical tools, data, and web services in a published paper embedded in evolving scientific discourse. We also consider how the live papers would influence the practice, culture, and economy of academic research. We conclude that geospatial researchers have an opportunity to lead this development towards richer and more open ways of communicating our findings. The technology and infrastructure to do so exist today, but several barriers remain. 相似文献
967.
Ground-motion predictions in Shillong region, northeast India 总被引:1,自引:0,他引:1
Sankar Kumar Nath Kiran Kumar Singh Thingbaijam Soumya Kanti Maiti Avinash Nayak 《Journal of Seismology》2012,16(3):475-488
We deliver ground-motion prediction equations for Shillong region, northeast India, based on a database generated by finite-fault stochastic simulations. An examination of the regional seismic source characteristics is carried out beforehand. Micro/minor earthquakes (M W?<?5.0) nucleating at hypocentral depth <21?km in the region recorded at broadband seismic stations are observed to have Brune stress-drop ranging between 2.8 and 99.9?bars. Likewise, macroseismic intensity data for the 1897 Shillong Earthquake that nucleated at a hypocentral depth of ~35?km places the associated stress-drop at 100?200?bars. The apparent variation of the stress-drop parameter with depth is considered with two source zones namely lower-crust and upper-crust. Equations for the lower-crust predict higher ground-motion levels and exhibit affinity to those developed for stable continental region of Eastern North America. The ground-motion levels predicted by the equations for the upper-crust are relatively lower but are still higher compared with those predicted for tectonically active regions, viz., the Himalayas and Western North America. 相似文献
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