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Some Aspects of Selection of Small Hydro Project Sites Using Remote Sensing and GIS
Published in C.V.J. Varma, A.R.G. Rao, Renewable Energy Small Hydro, 2020
Seismotectonic analysis has to be carried out while selecting small hydro sites in hilly terrains. The analysis is aimed at knowing the probable location of future earthquakes, frequencies of these occurrences, the extent of energy release and their impact at a construction site. Seismological, geological, geophysical and man-induced data base forms basic data for such analysis. Morphotectonic analysis involving interpretation of geological structures can be best attempted using the remote sensing data. Identification of faults and active faults can be done using aerospace (or its equivalents) data in conjunction with seismological data and supporting ground truth. Geologically active faults can be identified on the basis of certain features like fault scarp, rift valley, oversteepened base of mountain fronts, faceted triangular spurs or ridges, drainage offsets entrenched meanders, sag ponds, multiple river terraces, alignment/association of hot springs, stratographic offsets in younger unconsolidated sediments and many other elements [06].
Seismological investigation of deep structure of active faults using scattered waves and trapped waves
Published in H. Ogasawara, T. Yanagidani, M. Ando, Seismogenic Process Monitoring, 2017
Active faults are the structural boundaries where tectonic activities are concentratedly going on in the Earth’s surface (crust). Subsurface structure of active faults has been imaged by seismic reflection surveys at shallow depths (e.g. Ito et al. 1996). The structure at seismogenic depths, however, is still unknown for most of the active faults. After a large earthquake has occurred along a fault, its rupture process is estimated in detail from analyses of seismic and geodetic data (e.g. Wald & Heaton 1994). These studies and surface geologies along the fault suggest that heterogeneous fault structure such as asperities, step-over and bend has an important role on the complex rupture process of large earthquakes. It will be important to elucidate the deep heterogeneous structure along active faults not only for understanding the present tectonism around the fault but also for estimating the complex ruptures, therefore more realistic strong ground motion which may be generated by future large earthquakes. In this paper, several recent studies on imaging deep fault structure are discussed.
Main aspects in dam safety assessment and principles and concepts applied
Published in Ljiljana Spasic-Gril, Dams Safety and Society, 2023
Active faults result in breakages (ruptures) at the ground surface and the generation of seismic ground shaking. Neotectonically active faults are those with surface breaks during Neogene-Quaternary while recent active faults have breaks in the Holocene Epoch (c. 11,000 years before present) (ICOLD Bulletin 112). Contemporaneous active faults have historic evidence of surface breaking. The basic property of an active fault with surface rupturing capability (or “capable” fault in terms used by the International Atomic Agency) is a reasonable probability of producing a surface break during the lifetime of the dam. Active faults if present can compromise dam safety and integrity and therefore must be investigated as part of assessing dam site feasibility and design.
Seismicity pattern of African regions from 1964–2022: b-value and energy mapping approach
Published in Geomatics, Natural Hazards and Risk, 2023
Alemayehu Letamo, Kavitha B, Tezeswi TP
According to elastic rebound theory (Reid 1911), earthquakes are caused by the release of accumulated energy within fault raptures of rocks during sudden movements of tectonic plates. The distribution and mechanism of active faults, which are the source of significant seismicity, are crucial in seismicity studies. The map of active faults was recently compiled by Styron and Pagani (2020) under the project ‘The GEM Global Active Faults Database’. Figure 1 shows the mechanism of faulting for North Africa. It demonstrates that convergent northern Africa is subject to reverse faulting, and the formation of sizable thrust systems and orogenic belts (the Atlas and Betic/Rif chains) is primarily to responsible for the continent’s seismic activity. Diverging borders, however, show typical faulting (dextral and sinistral). It can be observed from Figure 2, that the East African rift system is now experiencing typical faulting in that it is a developing divergent tectonic plate boundary. Large earthquakes of various sizes have been recorded in historical and current times in the region around the triple intersection (Afar triangle). The area is dominated by normal faulting, according to the region’s surface geology and the focal mechanisms of earthquakes (e.g. Kebede and Kulhánek 1991; Ayele 2002), which is in line with current worldwide analyses of active faults by Styron and Pagani (2020).
Probabilistic seismic hazard analysis of the North-East India towards identification of contributing seismic sources
Published in Geomatics, Natural Hazards and Risk, 2023
Niranjan Borah, Abhishek Kumar
To the north of the Bengal Basin region is the Shillong Plateau region. This region was uplifted during the Late Cenozoic (Rao and Kumar 1997). The northern edge of the Shillong Plateau was again uplifted during the 1897 Shillong EQ (Oldham 1899; Bilham and England 2001; Vernant et al. 2014). Based on GPS data, Vernant et al. (2014) found that the Shillong block is rotating clockwise at a rate of 1.15°/Myr between longitudes 89°E and 93°E. Numerous active faults such as Dauki fault, Brahmaputra fault, Dapsi Thrust, Barapani Shear Zone, and Oldham fault exist in the region. Dauki Fault, which is an active north dipping reverse fault (Morino et al. 2011) separates the Shillong Plateau and the Bengal basin region. Brahmaputra fault is situated to the north of the Shillong Plateau (Dasgupta and Nandy 1982). Oldham fault triggered the great 1897 Assam EQ (Mw-8.1) while Dhubri fault triggered 1930 Dhubri EQ (Ms-7.1) (Bilham and England 2001; Nandy 2001; Kayal 2008).
Verification of Liquefaction Potential during the Strong Earthquake at the Border of Thailand-Myanmar
Published in Journal of Earthquake Engineering, 2022
Lindung Zalbuin Mase, Suched Likitlersuang, Tetsuo Tobita
Within the last five decades, the Thailand-Myanmar border has developed as the trading gate between Thailand and the surrounding countries of Myanmar, Laos, and China. The infrastructures are growing very fast in this area. However, earthquakes threaten this area each occurrence and could disturb the socio-economic aspects of this area. There are several active faults in this region that can potentially trigger significant earthquakes. On March 24, 2011, a strong earthquake of magnitude 6.8 Mw occurred in Tarlay, Myanmar (Mase, Likitlersuang, and Tobita 2018a), known thereafter as the Tarlay Earthquake, with an epicenter only 33 km away from the Thailand-Myanmar border. The earthquake not only resulted in huge damage to the infrastructures at the border region but also triggered a unique phenomenon called liquefaction (Mase, Likitlersuang, and Tobita 2018b). Soralump and Feungaugsorn (2013) also noted that the earthquake was the first recorded liquefaction event during the modern era of Thailand. Thus, studies of liquefaction in Thailand have focused on the Northern Part of Thailand, especially at the developing Thailand-Myanmar border region.