International Journal of Research ISSN NO:2236-6124 Earthquake Hazard Assessment for Dudhawa Dam of Chhattisgarh State (India) Ashish Kumar Parashar 1, Sohanlal Atmapoojya2 1Assistant Professor, Dept. of Civil Engineering, Institute of Technology,GGV (Central University) Bilaspur, India E-mail: [email protected] 2Professor, Department of Civil Engineering, K.I.T.S. Ramtek, Maharashtra, India, Abstract Earthquakes are caused by the sudden release of strain that has accumulated over time and are the most vicious natural hazards in the world, which manifest themselves in the form of vibrations of the earth. Recent years have witnessed an augment in awareness about earthquake and their sources and mitigations. Seismic Hazard analysis is a method of quantifying the area in terms of topographical and seismological data. The completeness of the data should be checked before carrying out the hazard analysis. For the present study a detailed catalogue of historical and recent seismicity within 300 km radius has been referred and liner sources were identified in and around the dam site. Earthquake data was analyzed statistically and the seismicity parameters, ‘a’ and ‘b’ of the region around Dudhawa Dam site of Chhattisgarh, India, has been evaluated. The outcomes are presented in the form of PGA using both deterministic seismic hazard analysis and probabilistic seismic hazard analysis with the estimation of % probability, for the probability of exceedance as 0.005g,0.01g &0.02g for a life span of 100 years. Keywords: Seismic inputs, Seismic hazard, DSHA, Peak Ground Acceleration, PSHA, Return Period. 1. Introduction Earthquakes, through their devastating effects - due to ground motion, earth faulting, tectonic deformation, soil liquefaction, landslides - are grave problem as faced by the modern society. Seismic hazard problem becomes more severe in recent years due to the fact that vulnerability is increasing, by the increase in urbanization and industrialization. The impact of the strong earthquakes occurred recently in different regions of the globe, draws attention to the necessity of taking urgent measures to reduce casualties and economic damages. An important tool to increase preparedness for earthquakes and to improve disaster prevention policies in densely populated areas is the seismic damage scenarios approach, including loss estimation. The occurrence of earthquakes in India is mainly observed, in the plate boundary of the Himalayan region as well as in the intra plate region of Peninsular India (P I). Devastating events have occurred in P I in the recent past, which must be considered as a severe warning about the possibility of such earthquakes in the near future. Particularly, in the case of dam sites, earthquake analysis is most important because, these are sensitive structures and any failure due to earthquake may cause havoc. Engineers design earthquake resistant structures, to mitigate the consequences of earthquake disasters, and educate new generations of experts in earthquake engineering by combining different physical, geophysical, and engineering sciences to serve our society. To evaluate the seismic hazards for a particular site or region, all possible sources of seismic activity must be identified and their potential for generating future strong ground motion needs to be evaluated. Identification of seismic sources require some detective work, nature’s clues, some of which are obvious and others quite obscure, that must be observed and interpreted. Seismic Hazard Analysis involves the quantitative estimation of ground-shaking hazards at a particular site. In the present study Seismic Hazard Analysis (SHA) has been used to asses Peak Ground Acceleration for a major dam site of the state of Chhattisgarh, i.e. Dudhawa Dam Site (20 ° 19 ′ 23 ″ N - 81 ° 45 ′32 ″ E). Volume 7, Issue XI, November/2018 Page No:1924 International Journal of Research ISSN NO:2236-6124 Dudhawa dam is located in Dhamtari District of Chhattisgarh in India. The construction of the dam began in 1953 and finished in 1964. It is built across the Mahanadi River in the village of Dudhawa, 21 km from Sihawa and 29 km from Kanker. The height of the dam is 24.53 m and the length 2,906.43 m. The reservoir has a catchment area of 625.27 km2 and it comes under Seismic Zone II. 2. Earthquake History of Study Area Chhattisgarh has very low rates of seismic activity but in the recent years, tremors from earthquakes in neighbouring states have been felt. Minor seismic activity has been recorded in the vicinity of Chiraikund and Muirpur along the border with Madhya Pradesh. A few faults which form the eastern section of the Narmada-Son Fault Zone have shown movement during the Holocene epoch. Another active fault is the Tatapani Fault which trends in an east-west direction in the vicinity of Manpura in Sarguja district. In the south, the Godavari fault, which forms the northern flank of the Godavari Graben, run through the southern part of the state and is also active. The following list briefly outlines known earthquakes in this region which either had observed intensities of V or higher (historical events) or had known magnitudes of M 4.5. 3.3 5.7 24 6.5 4.5 5.0 4.7 6.7 4.0 4.6 3.7 6.7 Narmada R. 23 6.5 4.8 4.8 ;Amarkantak 3.1 3.5 Mandla 4.3 4.3 4.9 Nainpur Maniari 6.0 F 4.8 F4 Chilpi Bilaspur F F3 5.8 Piparia F F5 22 Raigarh 4.0 4.8 Balaghat Katgi F F6 F2 4.6 5.3 R i Sambalpur d a F8 n Khair agarh a F F h a F9 M F F 3.9 F Raipur Dongargarh Bhandara Durg Bundeli Nagpur F Rajnandgaon F1 Binka F10 Baudh 21 F7 Mahanadi R. 4.4 Sagara 3.7 Phulbani 4.3 4.7 4.8 DUDHAWA DAM Doha R. Chanda F Latitude 20 3.9 R us h i Sorada ku l y a R P r an h ita R . Adaba 3.0 F11 Indravati R. 5.5 Jagdalpur F16 F F Sompeta V a m s a d Koraput h a 19 r F14 a G Parakimidi o F d a a u v N . a lt 3.0 a R 5.0 r g i a v a al r l a 3.3 V R a . l h le d y F a s Tekkali F m a 3.3 a u V l t N a g 3.1 P a a v r a 4.7 v li a F t i a p u u l t F r a 3.2 m F15 - 3.0 F F12 B o K b K 4.3 a b u n i 3.7 l 3.2 m a i d il F i a a 3.0 F F u a a l u u t l 3.4 6.0 3.0 F13 t lt 3.0 3.0 Vizianagaram 4.0 . 3.4 6.0 R 5.8 u 4.8 r il e 5.3 3.3 S 18 3.2 5.0 4.5 4.3 3.0 . R i r 4.5 a b 3.7 a 5.5 3.2 S 4.3 4.5 5.8 4.4 3.7 4.7 4.5 3.7 4.5 3.1 3.1 3.4 4.3 3.2 3.7 4.8 17 78 79 80 81 82 83 84 85 Longitude Fig. 1 Seismotectonic Map of Dudhawa Dam Site and Surroundings In the present study Dudhawa Dam Site was selected as the target. The fault map was structured from Seismotectonics Atlas of India. A control region of radius 300 km around the Dam Site, having centre at 20 ° 19 ′ 23 ″ N - 81 ° 45 ′32 ″ E, was considered for further investigation. The fault map of this circular region Fig. 2 reflects that in recent years, seismic activity appears to be concentrated along Godavari Valley Fault (130 km). A total of fifteen major faults, are seen to influence seismic hazard at Dudhawa Dam Site. Fault details are tabulated in Table 1. After going through various available literatures and sources such as (USGS, NIC), 96 Nos. of earthquakes in the magnitude ranges 3< Mw <6.7 for Dudhawa Dam Site, occurring over the period from 1827 to 2012 were identified for the present study. Volume 7, Issue XI, November/2018 Page No:1925 International Journal of Research ISSN NO:2236-6124 Table 1 Dudhawa Dam Site Faults Considered for Hazard Analysis Min. Map Hypo Central Weightage Fault no. Length, L i Focal Depth Distance Distance, R Wi=Li/ ∑Li (km) (km) (km) (km) F1 26 289.756 10 289.929 0.0220 F2 75 271.966 10 272.150 0.0634 F3 38 297.007 10 297.176 0.0321 F4 91 271.613 10 271.798 0.0769 F5 70 240.306 10 240.514 0.0592 F6 58 127.985 10 128.376 0.0490 F7 25 166.533 10 166.833 0.0211 F8 45 180.596 10 180.873 0.0380 F9 70 237.523 10 237.734 0.0592 F10 125 220.980 10 221.207 0.1057 F11 180 237.443 10 237.654 0.1522 F12 130 236.667 10 236.879 0.1099 F13 32 287.825 10 287.999 0.0270 F14 121 218.039 10 218.269 0.1023 F15 46 283.577 10 283.754 0.0389 F16 51 255.875 10 256.071 0.0431 2.1 Catalogue Completeness In 1972, Steep proposed a method based on the length of the period , over which a particular magnitude is complete. In this method, catalogues are grouped into several magnitude ranges and each magnitude range is considered as a point process in time.