Liquefaction hazard assessment and building foundation safety for Chennai city, India

Rajarathnam S., Renu M. S., Santhakumar A. R. and Premalatha K.

Chennai is India’s 4th largest metropolitan city having a multi-dimensional growth in development of its infrastructures and population. The city is prone for moderate seismic activity and the anticipated earthquake is with magnitude of 6.5 based on past earthquake history. The Chennai city with variety of geological deposits and the geotechnical characteristics of sediment deposits has its own importance on ground movements. Liquefaction is one of the most destructive phenomena caused by earthquake and especially in loose saturated sand deposit. Hence there is a need to prepare liquefaction hazard map which will enable urban planners to design earthquake resistant structures and strengthen existing unstable structures. In this study, SPT data from 666 boreholes was used to evaluate the liquefaction potential. A Liquefaction Hazard Map is prepared and the result has been correlated with various geological deposits. It shows that the marine deposits has higher liquefaction hazard compared to that of fluvial deposits. Among marine deposits, the paleo tidal litho unit is more prone for liquefaction compared to strand flat and tidal flat litho units. The result shows that the liquefaction layer thickness varies from 1m to 10m. The Severity of Liquefaction (SL) is calculated for Very Severe and Severe categories of Factor of Safety (FS) and utilized to arrive the pile diameter for preventing of buckling of building foundation piles. In this study, over 50,000 buildings from 3 to 14 stories have been studied to evaluate the foundation stability against the sand layer thicknesses of liquefiable zones. Generic recommendations for shallow foundation and deep foundation of multi-storied buildings have been suggested to mitigate against the effect of liquefaction hazard for building foundation safety.

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The Case of the Mw 8.8 Mega Earthquake of Central Chile: Analysis applying an Accident Investigation Model

Alvarado-Corona1 R., Mota-Hernández C., Félix-Hernández J. L. and Santos-Reyes J.

The impact, in its various facets, caused by natural disasters is increasing sharply. Poor resilience contributes to increasing the impact on society throughout history; natural disasters have exerted a heavy toll of death and suffering. Given this, natural disasters present a big challenge to society today concerning how they are to be mitigated so as to produce an acceptable risk is a question which has come to the fore in extreme ways recently. The Mw 8.8 Maule earthquake of 27 February 2010 has been studied in great detail. The paper presents some preliminary results of the analysis of the Chilean earthquake that occurred in February 2010 by applying the Management Oversight Risk Tree (MORT) model. The MORT may be regarded as a structured checklist in the form of a complex fault tree model that is intended to ensure that all aspects of an organization’s management are looked into when assessing the possible causes of an incident. The MORT accident investigation model has been applied extensively to the analysis of accident/incidents that have occurred in industries such as the oil and gas, nuclear, aviation etc. It may be argued that the model has the potentiality to be applied to the analysis of natural disasters such as mega earthquakes. It is hoped that by conducting such analysis, lessons can be learnt so that the impact of natural disasters such as the Chile´s Mega Earthquake can be mitigated in future similar events.

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Morphometric investigations in Kattery Watershed, South India using Remote Sensing and GIS techniques

Kasiviswanathan S. P., Subramani T., Suresh M. and Karunanidhi D.

Morphometric analysis of Kattery watershed in and around Achanakal, South India has been carried out using remote sensing and GIS techniques. These techniques are found relevant for the extraction of watersheds and drainage networks. The extracted drainage networks were classified according to Strahler’s system of classification which reveals that the terrain exhibits dendritic to sub-dendritic drainage pattern. Morphometric analysis was carried out at mini-watershed level using spatial analysis tool in GIS. The Kattery watershed is sprawled over an area of 137.32 km2. The study area is designated as fifth-order watershed and lower order streams mostly dominate the watershed with the mean drainage density value of 2.73 km/km2. The slope of basin varies from gentle to 52.65° and the slope variation is chiefly controlled by the local geology and erosion cycles. The primary parameters of morphometric analysis such as watershed area, watershed perimeter, watershed length and stream length were measured using GIS, which were further used to obtain the derived parameters such as drainage density, drainage texture, bifurcation ratio, stream length ratio, stream frequency, form factor, elongation ratio and circulatory ratio. The assessed morphometric parameters were clustered as linear, relief and areal parameters. Geomorphologically, the dissected upland is noticed in all the mini-watersheds which occupy 60.72% of the Kattery watershed. Bhavani and Kattery watersheds are fully covered by dissected upland. Kattery watershed is an elongated basin with high to moderate relief and steep slope. This may be due to the high to medium elongation ratio (0.92 to 2.29). Morphometric classification of Kattery watershed is mainly done based on the stream frequency and drainage density which actually control the runoff pattern, soil erosion, sediment transportation and mass movement. Drainage analysis indicates that the low density exists in Arayatti, Wellington, Karumpalam, Kattery-1, Kattery-2 and Aravankadu mini-watersheds indicating low relief and more permeable subsurface materials. Hence, from the study, it can be concluded that remote sensing data (SRTM–DEM) coupled with geospatial techniques prove to be a competent tool in morphometric analysis and the data can be used for watershed management, control of soil erosion and landslide mitigation.

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Ramification of flood disaster in Uttrakhand

Cresenta Shakila Motha L., Alamelu R., Sivasundaram Anushan S.C. and Badrinath V.

The flash floods triggered by the incessant rains in the upper Himalayas during 14 to 17th June resulted in chain of landslides and floods in the Northern India. The state of Uttarakhand had been drastically affected the most. This descriptive study analyzed the post traumatic impact of flood disaster among the rescued survivors of Uttrakhand State. In general, disaster leads to physical and social impact making people vulnerable and distressed even a year after the calamity. Despite the difficulty in measuring these socio-economic and psychological impacts, they had caused significant problems for the long-term functioning of specific types of households and businesses in the affected communities. The flood had caused detachment of more than hundred villages from connectivity and people experienced difficulty in getting basic amenities. In this regard, the researchers had adopted area sampling method to include two districts Dehradun and Chamoli. This study revealed the fact that a year after the devastation, in spite of various rehabilitation activities carried out to perk up the physical, economic, social, emotional, behavioural and cognitive conditions, only little has changed to improve the living standards of disaster survivors. There is yet a long way to go for the recovery of these troubled communities to come back to normalcy.

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Ionospheric Situation from Huge Gas Explosion in Kaohsiung City in Taiwan on 31 July 2014

Jyh-Woei Lin

This paper used two-dimensional Principal Component Analysis (2DPCA) to determine total electron content (TEC) respond in the ionosphere for the huge gas explosion in Kaohsiung, Taiwan at 15: 59 (UT) on 31 July 2014. Results have shown TEC anomaly over Kaohsiung and Taiwan from 16:00 to 16:05 (UTC) with the duration time of 5 minutes. Potential causes of the results were discussed with emphasis given to acoustic shock waves with the speed of 2500m/s and caused a TEC anomaly. Supposedly, it is possible to predict this explosion time due to the gas release just short time before this explosion if such explosion is very huge to reduce the number of dead people.

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Evaluation of seismic stability for mud houses based on various existing and proposed layouts

Mohamad Shahrukh S., Majumder Deepnath, Ramanathan Abhishek, Tangudu Sweeya and Bhattacharya S. P.

Midnapore, a district located in southern West Bengal, India, falls under a mild earthquake hazard zone. But during the recent earthquakes at Andaman and Nicobar Islands and Sikkim, this region experienced not so ‘mild’ shocks. The repercussions of such earthquakes in the urban areas are indisputable. But we cannot overlook the fact that rural areas still contain more than 60% of the population in India. 3 High levels of poverty and lack of resources and expertise to mitigate and respond to disasters render these denizens defenseless against such hazard events. Also the physical conditions of their housing are poor and hence are presently exposed to greater seismic risk. This study presents a seismic evaluation of the rural built forms, predominantly mud houses and prescribes design provisions to mitigate the same. The rural buildings are modeled and seismic forces are evaluated based on a physical survey. Various planar building layouts are examined and a comparative analysis is made. Analysis has also been done to investigate various options for expansion and a comparison chart is prepared. In addition to this, economically viable methods of retrofitting have been suggested.

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Seismotectonics of the Lithospheric Subduction in the Eastern Indian Ocean

Lasitha S.

Geological and tectonic characteristics of the Andaman-Sumatra-Java arc change significantly along strike. The deformation field suggests that a pure normal subduction dominated by thrust faulting in the Java region becomes progressively oblique towards Sumatra and the Andaman arc characterized by thrust faulting and right-lateral shear motions in Sumatra region, dominantly strike-slip and normal faulting in the Andaman region. Seismicity does not extend below 200 Km in Andaman and below 350 Km in Sumatra. Deep earthquakes start to appear beyond 105¬¬o between Sunda Strait and Java arc region where earthquakes in the WBZ can occur at a depth of 600 to 650 km. However, a gap in seismic activity is observed in Andaman at a depth range of 90-110 Km and in Sumatra at a depth range of 90-220 Km and at intermediate depths of 300-500 Km below Java arc region. The presence of such aseismic gaps has been interpreted as a loss of brittle character of the slab at the respective depth. In spite of it, the slab is continuous and penetrates into the lower mantle which can be interpreted as a manifestation of still seismically active part of the Tertiary Subduction zone buried in the upper mantle22.

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Disaster rapid mapping of burnt area using relative radiometric correction from multi-temporal Satellite images

BoYeol Yoon and JongMin Yeom

In the present study, we focus on the disaster rapid mapping of burnt area in South part of Australia from multi-temporal satellite image processing based on relative radiometric correction. Multi-temporal scenes from Landsat 5 satellite were processed using the Multivariate Alteration Detection (MAD) method which has a particular advantage of selecting PIFs (Pseudo Invariant Features) automatically by canonical correlation analysis. This method is proposed for the automatic extraction of changed areas after the forest fire using relatively normalized reflectance via MAD method done within a high accuracy level. In addition, the relative correction of multi-temporal satellite imagery produced better results to rapidly map disaster-affected areas with an increased confidence level when comparing with ordinary image difference method.

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