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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].
Ground subsidence
Published in F.G. Bell, Geological Hazards, 1999
Those faults that are suspected of being related to groundwater withdrawal are much less common than fissures. They frequently have scarps more than 1 km in length and more than 0.2 m high. The longest such fault scarp in the United States is 16.7 km long, and the highest scarp is around 1 m, both being in the Houston—Galveston region which is the most affected by such faulting in the United States. These fault scarps have been found to increase in height by dip-slip creep along normal fault planes. Measured rates of vertical offset range from 4 to 60 mm annually; however, movement tends to vary with time. Although some short-term episodic movement has been reported, seasonal variations of offset that correlate both in magnitude and timing with seasonal fluctuations of water level are remarkably widespread (Holzer, ibid.). The land surface near a scarp may tilt, tilting being greatest near a scarp but having been observed to extend as far as 500 m from a scarp.
Structure and landforms
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
Hans Cloos has provided a classification to aid in the explanation of the geomorphic expression of faults (Figure 7.26), depending on the relative rates of displacement and erosion (A, B and C), on the possibility of renewed (posthumous) faulting (E) and the differential erosion on either side of a stable fault plane (F and G). Thus (Dennis, 1972): A is a faulted sequence of considerable faulting rate and negligible erosion producing, first, a monoclinal flexure (1) which breaks into a fault (2) (e.g. the East Kaibab Monocline, Colorado Plateau: see Figure 7.6), and then becomes a significant fault scarp (3) whose height represents the vertical throw of the displacement and slope length the dip-slip of the fault.B is an intermediate condition of erosion and uplift occurring together. The rising block is eroded by headward valley-cutting, at the margins of which alluvial fans are built and other deposits are laid down on the subsiding block (1–2). Continued erosion produces characteristic triangular truncated spur facets on the fault scarp (3), as does the advent of active erosion on an existing fault scarp (A3) (see Figure 7.27A).C has an erosion rate which greatly exceeds the uplift rate of the rising unit such that there is a general flattened surface across the fault zone (1), except where differential erosion can form small scarps (2 and 3).D represents the condition after cessation of fault movement and the completion of erosional truncation and depositional filling.E condition D interrupted by renewed (posthumous) faulting and the production of a new fault scarp (2) (see Figure 7.27B).F stability along the fault plane may continue but renewed erosion produces a further excavation of the fault to produce a resequent fault-line scarp (i.e. fault line because it has been produced entirely by erosion, and resequent because it faces the original downthrow side).G On the other hand, if erosion during stability excavates a scarp facing towards the original upthrow side, due to chance lithological associations on either side of the original fault plane, an obsequent fault-line scarp is produced.
Paleoseismology of the Hyde Fault, Otago, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2022
Jonathan D. Griffin, Mark W. Stirling, David J.A. Barrell, Ella J. van den Berg, Erin K. Todd, Ross Nicolls, Ningsheng Wang
Previous mapping of the fault trace (Forsyth 2001; Villamor et al. 2018; Barrell 2021) was updated using a 1 m horizontal resolution DEM constructed from a lidar dataset (with resolution of 2.68 points/m2) acquired by the Otago Regional Council in 2016 (Figure 2). Using the DEM and derived products (slope and contour maps, and topographic profiles taken along fluvial gradients across the scarp), we mapped the extent of active fault scarps along the range front, and mapped and correlated alluvial fan surfaces. Fault scarps were identified in topographic profiles as breaks in slope, and distinguished from fluvial features (e.g. terrace risers) by continuity of the scarp across topographic gradients. Topographic profiles were also used to measure the vertical offset of fan surfaces in the vicinity of the trench sites. Interpretation of the lidar-based mapping was verified by field investigations at the trench sites.
Geomorphic analysis of Xiadian buried fault zone in Eastern Beijing plain based on SPOT image and unmanned aerial vehicle (UAV) data
Published in Geomatics, Natural Hazards and Risk, 2021
Yanping Wang, Pinliang Dong, Yueqin Zhu, Jun Shen, Shunbao Liao
Main methods employed in this study include remote sensing image analysis, field survey, micro-geomorphic feature analysis, historical documents analysis, evolution law analysis of fault scarp and stress field analysis of fault zone, as shown in Figure 2.