The rapid development of urban areas and the increase in construction activities have resulted in a scarcity of land with favorable soil conditions, necessitating the use of locally available weak soils for construction activities through stabilization techniques. This study introduces a new material, areca fiber, and its suitability as soil reinforcement. Although areca is available abundantly in many parts of the world, its application in geotechnical engineering has not been explored. In the present study, bottom ash (BA) is used as a stabilizing agent, and the suitability of natural areca fiber as reinforcement is demonstrated through detailed experimental investigations and reliability analysis. The test method includes compaction tests, unconfined compression strength (UCS) tests, California bearing ratio (CBR) tests, and split tensile strength tests. The BA content was varied from 0 to 40%, the fiber content was varied from 0 to 1.5%, and the corresponding performance assessment was done. A small amount of cement (3%) was also added to improve the pozzolanic reaction. The UCS and split tensile strength tests were conducted on samples at different curing periods with a maximum curing for 90 days, whereas CBR tests were conducted after 7 days of curing for both soaked and unsoaked conditions. There was considerable increase in UCS, CBR, and split tensile strength of the soil with addition of BA, and the strength values increased tremendously in the presence of areca fiber. Mineralogical and microstructural studies were conducted on the stabilized soil sample using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. These results confirmed the formation of cementitious compounds in the XRD patterns and showed development of dense matrix in the SEM images. The performance of the modified subgrade soil was validated using a reliability approach, which found that the soil subgrade with BA and areca fiber can certainly be used as pavement material for low-volume applications.

This paper presents spatial variation of seismic hazard at the surface level for India, covering 6–38° N and 68–98° E. The most recent knowledge on seismic activity in the region has been used to evaluate the hazard incorporating uncertainties associated with the seismicity parameters using different modeling methodologies. Three types of seismic source models, viz. linear sources, gridded seismicity model and areal sources, were considered to model the seismic sources and different sets of ground motion prediction equations were used for different tectonic provinces to characterize the attenuation properties. The hazard estimation at bedrock level has been carried out using probabilistic approach and the results obtained from various methodologies were combined in a logic tree framework. The seismic site characterization of India was done using topographic slope map derived from Digital Elevation Model data. This paper presents estimation of the hazard at surface level, using appropriate site amplification factors corresponding to various site classes based on VS30 values derived from the topographic gradient. Spatial variation of surface level peak horizontal acceleration (PHA) for return periods of 475 years and 2475 years are presented as contour maps

Online material : Earthquake catalog; coordinates of source zones; list of events in each zone; frequency magnitude distribution plots. Identification and characterization of seismic sources are essential input for seismic hazard analysis. A complete and consistent catalog of earthquakes in a region can offer good data for studying the distribution of earthquakes with respect to space, time, and magnitude. Earthquakes are known to have occurred in the region of the Indian subcontinent from historic times. Most of the activities, including many great earthquakes, have occurred in the northern subcontinent and in the Andaman and Nicobar regions. In the southern peninsula, damaging earthquakes have occurred, but their frequency was less and magnitudes were lower than the plate boundary earthquakes. The tectonic framework of the Indian subcontinent—an area of about 3.2 million square kilometers—is complex and varied spatially. This necessitates identifying different regions of similar seismicity. In this study we attempt to identify and characterize regional seismic source zones based on a homogeneous catalog of earthquakes in and around India from 250 BC until 2010. We identified different regional seismic source zones and created separate catalogs for each respective zone. Most earthquake catalogs do not report earthquake magnitudes consistently over time, which may hinder defining seismicity patterns or assessing seismic hazards. The magnitude scales used for earthquake catalogs in India are not homogeneous. Compiling a complete catalog of earthquakes with uniform magnitudes is essential for defining seismicity patterns and assessing seismic hazards for a region (Chen and Tsai 2008). Hence the original magnitudes of earthquakes have to be converted to a common and reliable magnitude scale using appropriate magnitude correlations. In the raw catalog, many events can be dependent events that occurred in association with a mainshock in a cluster. These aftershocks and foreshocks have to be removed from the catalog using …