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Seismic Microzonation of a Region Based on Seismology and Geological Data International Journal of Advanced Research in Engineering and Technology (IJARET) Volume 8, Issue 6, November - December 2017, pp. 55–64, Article ID: IJARET_08_06_006 Available online at http://iaeme.com/Home/issue/IJARET?Volume=8&Issue=6 ISSN Print: 0976-6480 and ISSN Online: 0976-6499 © IAEME Publication SEISMIC MICROZONATION OF A REGION BASED ON SEISMOLOGY AND GEOLOGICAL DATA R. Manigandan Department of Civil Engineering, College of Engineering Guindy, Anna University, Chennai, Tamil Nadu, India R. Thiyagarajan Teaching Fellow, Department of Civil Engineering, College of Engineering Guindy, Anna University, Chennai, Tamil Nadu, India ABSTRACT In current and past, massive earthquakes have leads to an huge loss of lives and non-lives in the world (Armenia, 1988; Iran, 1990; US, 1994; Japan, 1995; Turkey, 1999; Taiwan, 1999, India 2001, Sumatra 2004, Pakistan, 2005, China 2008,) On January 26, India’s 51 republic day 2001 at 08:46AM local time (3:16 UTC) Bhuj Earthquake, one of the major devastating earthquakes ever to strike India occurred in the Kachchh region of Gujarat in western India. The magnitude of 7.9(Mw) (6.9 Richter scale), and the depth of 16 Km(10mi), the damage was very big impact is round the radius of 350kms. The epicenter was about 9km south-southwest of the village of chobari in bhachau taltauka of kutch district of Gujarat, including major cities like Ahmedabad, Bhavnagar and Surat at a distance of 240 km, 275 km and 350 km respectively. The damage incurred as well as past earthquake depends not only on the intensity of the earthquake magnitude (source) but, in consideration to a large extent, on the medium scale through which the seismic waves propagate (path of waves propagation and site effects like soil condition) and the social-economic development of the human settlement (Panza et al., 2001). Many huge cities in India are situated in the severe earthquake hazard threat in the vicinity of Himalayan region and even in peninsular shield. Macrozonation map in Indian seismic code 1893 is frequently revised soon after a major earthquake. New revision was published in 2002 after Bhuj earthquake in 2001, which is of many recent earth quake is to be considered in with adequate data at an new revision to contains four macro zones. Revision of the map can efficiently be done by considering the geotechnical aspect of the regions. Microzonation is an effective tool and a preventive step for reducing the impact of earthquake in a particular region. The Microzonation map allows us to characterize the seismic potential areas, which are important in the design of structures. It is done by the sub division of region into micro zones. The present study presents a review on the development of the seismic microzonation studies. Seismic microzonation work has been carried out in India in http://iaeme.com/Home/journal/IJARET 55 [email protected] Seismic Microzonation of a Region Based on Seismology and Geological Data some of the important mega cities that have the potential of being damaged from future earthquakes. As part of the national level microzonation programme, department of science and technology, Government of India has done microzonation of 63 cities in India. Some of them are finished and some of them are ongoing. As an initial experiment, seismic hazard analysis and Microzonation was taken up for Jabalpur city in Madhaya Pradesh. Further, for many other cities such as sikkam, Mumbai, Delhi, North east India, Gauwhati, Ahmedabad,Bhuj and Chennai an attempt has been made to carry out microzonation considering geomorphological features and detailed geotechnical studies. In this paper, the Microzonation studies carried out in different cities of India with different methodologies used by various researchers will be discussed. Further, the merits and limitations of these studies have also been highlighted. Seismic Microzonation studies in India lack few aspects/issues which can be broadly classified into three groups: 1. Seismology (features). 2. Grade and geology related (past and current data). 3. Geotechnical related issues. Most of Microzonation studies do not have proper regional seismotectonic maps for the study area. Seismic Microzonation maps published are based on deterministic seismic hazard analysis for different possible scenario earthquakes. This may be improved by considering uncertainties involved in the earthquake and produce the hazard map with required probability and return periods. Seismic Microzonation maps produced does not have a uniform scale, which may be generalized under the uniform grade and scale of mapping. Importance of geology plays a major role in Microzonation studies in India, which is inadequate to represent local site effects. More importance shall be given to geotechnical Key words: Microzonation, Mapping, Seismic, Geotechnical, Earthquake, Hazards, Epicenter. Cite this Article: R. Manigandan and R.Thiyagarajan, Seismic Microzonation of a Region Based on Seismology and Geological Data. International Journal of Advanced Research in Engineering and Technology, 8(6), 2017, pp 55–64. http://iaeme.com/Home/issue/IJARET?Volume=8&Issue=6 1. INTRODUCTION Seismic Microzonation is a subdividing of a region into smaller areas having different potential for hazardous earthquake effects. The earthquake effects depend on ground geomorphological attributes consisting of geological, geomorphology and geotechnical information. The parameters of geology and geomorphology, soil coverage/thickness, and rock outcrop/depth are some of the important geomorphological attributes. Other attributes are the earthquake parameters, which are estimated by hazard analysis and effects of local soil for a hazard (local site response for an earthquake). The Peak Ground Acceleration (PGA) [from deterministic or probabilistic approach], amplification/ site response, predominant frequency, liquefaction and landslide due to earthquakes are some of the important seismological attributes. Weight of the attributes depends on the region and decision maker, for example flat terrain has weight of “0” value for landslide and deep soil terrain has highest weight for site response or liquefaction. http://iaeme.com/Home/journal/IJARET 56 [email protected] R. Manigandan and R.Thiyagarajan Seismic zoning consists of subdividing a national territory into several seismic zones indicating progressive levels of expected seismic intensity or peak ground acceleration for different return periods based on historic and predicted intensity of ground motion. It is common to see countries classified into three, four or more seismic zones and seismic design requirements for buildings are generally the same within a defined seismic zone. Such maps are small scale maps covering a large territory. Seismic microzoning provides detailed information on earthquake hazard on a much larger scale. It recognizes the fact that spectral acceleration values for sites within a seismic zone vary in tune with the location specific geological conditions. It therefore consists of mapping in detail all possible earthquake and earthquake induced hazards. It necessarily involves seismological, geological, geotechnical and hydro-geological mapping and their integration to provide a picture of levels of hazard distribution comprehensible to urban planners, engineers and architects. Levels of Seismic Microzonation generally float with the choice of scale of mapping as also with the degree and scope of scientific investigation fashioned to minimize uncertainties in seismic hazard evaluation for a specific set of objectives. The quantum and quality of basic maps and information required for making a head with the mapping work are rarely available. Since seismic microzonation work cannot wait for all the required information, a first cut microzonation map is prepared based on a minimum programme of investigation. Choosing an appropriate mapping scale and thinking to scale while mapping are the two challenges common to every such programme. What is to be included and what is to be left out for future investigation will have to be decided on a case to case basis. Degree of detailing and scrutiny expands with increase of mapping scale. Figure 1 Three Grades of Seismic Microzonation Recommended by the Technical Committee of International Society of Soil Mechanics and Foundation Engineering [ISSMF] Three levels of Seismic Microzonation expressed as Grade1: General Zonation; Grade 2: Detailed Zonation and Grade 3: Rigorous Zonation were favoured by the Technical Committee on Earthquake Geotechnical Engineering of the International Society of Soil Mechanics and Foundation Engineering (1993). The recommendation essentially meant making a beginning with relatively small scale mapping and move on to higher levels of microzonation by obtaining added quality inputs that could justify large scale mapping. The population of the country is crossing leaps and bounds and a great revolution is taking place in the human living standards. The developments are seen in various fields, but when we come across the natural disasters that have been occurred in the past history, we can see a http://iaeme.com/Home/journal/IJARET 57 [email protected] Seismic Microzonation of a Region Based on Seismology and Geological Data great destruction in the society. India has been facing the threat of earthquake quite from ancient time. Earthquake is one among the major natural disasters that are been created due to the seismic waves generated from plain bed region. Earthquakes come up with a devastating
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