Cyclic behavior of late quaternary alluvial soil along Indo-Gangetic Plain: Northern India

The A.D. 1803 and 1934 Bihar-Nepal border earthquake affected Indo-Gangetic Plain with evidences of liquefaction in cities like Patna, Varanasi, Agra, and Delhi in historical past. Recent strong shaking all along the Indo-Gangetic Plains and seismic induced damage to the buildings in Bihar during Mw 7.8 Gorkha earthquake raises the concern for site specific liquefaction potential estimation of alluvial soils. Cyclic triaxial tests were conducted on soil samples from Kanpur, Allahabad, Patna city to know the cyclic behavior, estimate the dynamic soil properties and the effect of relative density, confining pressure and frequency of loading on the cyclic behavior of the soil tested. The test results indicate the cyclic strength of Allahabad soil is less than Patna and Kanpur soil. The Allahabad soil with 80% sand, 10% silt and clay each is more prone to liquefaction than Kanpur soil (82% silt, 16% clay and 2% sand) and Patna soil (10% Kankar, 95% sand, 5% silt). This study indicates soils having sand with silt percentage are more liquefiable than clean sand or silty soil. It can be concluded that the soil of Allahabad and Patna city is more prone to liquefaction than Kanpur soil.

Crustal structure of central Myanmar (Burma) By surface wave dispersion

Digital records of seismic waves observed at Seismic Research Observatory, Cheng Mai. Thailand have been analysed for two earthquakes in western Nepal. Digital data are processed by the floating filter and phase equalization methods to obtain surface waves free from noise. Group velocities of Love and Rayleigh waves are obtained by frequency time analysis of these noise free surface waves. The period of group velocities ranges from 17 to 62 sec for fundamental mode Rayleigh waves and from 17 to 66 sec for fundamental mode Love waves. The wave paths cross both central Myanmar (Burma) and the Indo-Gangetic plain. The group velocity data of surface waves across central Myanmar (Burma) have been obtained after correction of the data for the path across the Indo-Gangetic plain. Inversion of data gives the average crustal and subcrustal structure of central Myanmar (Burma). The modelled structure shows two separate sedimentary layers each of 8 km thick, The lower sedimentary layer forms the low velocity zone of the crust. The total thickness of central Myanmar (Burma) crust is found to be 55 km

Latest seasonal trend of aerosol, particulate matter and ozone in Delhi

In this work, latest seasonal variation of aerosol, particulate matter and ozone in Delhi has been studied. Observations show that during winter, concentration of surface O3 is low and that of PM2.5 and PM10 is high. Aerosol size and aerosol content increases during winter. Decrease in surface ozone is explainable by gas phase and heterogeneous chemistry. An interesting feature is, along with surface ozone, total ozone also shows a low value during winter. This is a characteristic of ozone in Indo-Gangetic plain. Indo-Gangetic plain is covered by mild to heavy fog during most of the days in winter. It is possible that increase in size and content of aerosol and PM particles coupled with low temperature, low solar flux and high humidity is the cause of fog formation during winter in Indo-Gangetic plain.

High aerosol loading over mega city Delhi in the western Indo-Gangetic plain : Optical characteristics

Measurements of aerosol optical properties were carried out at an urban mega city Delhi, which is situated in the western Indo-Gangetic Plain (IGP) region in north India using an automatic sun/sky radiometer during 2006-2008. The present study revealed high aerosol loading over the station, which could be due to its topography surrounded by different natural and anthropogenic emission sources, and may have major implications towards health, air quality and climate system. Results show a large variability in AOD during the study period, with nearly equal values during winter (0.67 ± 0.06) and summer (0.71 ± 0.11). The Ångström exponent (AE) values were found to be relatively higher during winter (1.19 ± 0.07, suggests dominance of fine-mode aerosols) and lower during summer (0.74±0.06, suggests dominance of coarse-mode aerosols). A slight decrease in single scattering albedo (SSA) was observed during the study period, with a mean value of ~0.9. SSA was found to be about 0.93 during post-monsoon and 0.96 during the winter period whereas during summer and monsoon, SSA was about 0.95. The estimated monthly absorption Ångström exponent (AAE) values over the station varied from 0.11 to 1.87, which were found to be less than 1.0 by ~55% time (mostly during winter and monsoon), and greater than 1.0 by ~45% time (mostly during summer and post-monsoon).