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Engineering Seismology Overview
Published in Hector Estrada, Luke S. Lee, Introduction to Earthquake Engineering, 2017
The fault slip is used to classify faults depending on the direction of the movement of rocks on one side relative to the other side; vertical movement is known as dip-slip, while horizontal movement is known as strike-slip. These terms correspond to the definition of the angles used to describe the direction of fault movement. As discussed in Section 1.2.3, faults occur along the edges of tectonic plates (or their interior, which is much less common). Dip-slip faults are further subdivided based on the relative vertical movement of the tectonic plates: normal faults occur at plate boundaries where tectonic plates spread apart at divergent zones causing the hanging wall to move down relative to the footwall, while reverse faults occur at plate boundaries where tectonic plates collide at convergent zones causing the hanging wall to move up relative to the footwall; see Figure 2.2. Thrust faults are reverse faults with a small dip angle. Faults along oceanic ridges are normal, resulting in the lengthening of the crust, as shown previously in Figure 1.11, whereas those along subduction zones are reverse, resulting in the shortening of the crust. When these faults break through to the surface, surface rupture, they produce an exposed steep slope known as the fault’s scarp; see Figure 2.2.
Tectonics and Sedimentation
Published in Supriya Sengupta, Introduction to Sedimentology, 2017
Strike-slip faults may occur either at the major plate boundaries or at the border of microplates. Transform faults occur as fracture zones running across the midoceanic ridges. The overall movement in a strike-slip fault is essentially horizontal and parallel to the fault trace but the dip-slip component may also be important locally. This oblique movement causes the strike-slip motion to be either divergent (transtensile) or convergent (transpressive). The former is likely to produce normal faulting, leading to basin development and volcanism. The latter produces reverse faults, thrusts, uplift and folding. With the passage of time, a divergent strike-slip fault may be converted to a convergent one.
Seismology and site effects
Published in Mark Aschheim, Enrique Hernández-Montes, Dimitrios Vamvatsikos, Design of Reinforced Concrete Buildings for Seismic Performance, 2019
Mark Aschheim, Enrique Hernández, Dimitrios Vamvatsikos
Faults are planar fractures or discontinuities where relative displacement or movement has occurred. Faults are classified based on the different types of movement that can appear (Figure 2.2). Strike-slip faults are characterized by relative horizontal displacements as the two segments appear to be sheared relative to each other. Normal and reverse faults display vertical movement whereby one segment is pulled or pushed, respectively, against the other along a sloping fault plane. Thrust faults are essentially reverse faults with a nearly horizontal fault plane.
Integration of SPOT-5 and ASTER satellite data for structural tracing and hydrothermal alteration mineral mapping: implications for Cu–Au prospecting
Published in International Journal of Image and Data Fusion, 2018
Reyhaneh Ahmadirouhani, Mohammad-Hassan Karimpour, Behnam Rahimi, Azadeh Malekzadeh-Shafaroudi, Amin Beiranvand Pour, Biswajeet Pradhan
The results indicate that highest intensity and density value and the intersection of the fractures are similar to fractal analysis (concentrated in the NW and SE zones) and the NW-SE is the main trend of the faults, fractures and regional structural system in the Bajestan region (Figure 4(a–d)). Furthermore, fieldwork was implemented to check and verify the fracture map results. The structure of this area is probably affected by the activity of deep strike-slip faults in the boundary of the structural blocks (shear zone structural style in a strike-slip system). In the Bajestan area, all of the rock units, especially the granitoids are dissected by numerous fractures due to the regional stress. Main fractures in this area show an azimuth of 100° to 130° an average dip of 85° and NE trend of dip direction. The trace length of the faults varies from 5 to 3000 m with varying frequency in the number. Felsic and basic dikes have also been emplaced along the major fracture system in the region. Essentially, two main orientations of NW–SE and NE–SW were derived from remote sensing and fieldwork data, which NW-SE orientation is associated with many of the hydrothermal alteration zones and Cu–Fe–Au vein-type ore mineralisation in the Bajestan area. Figure 5(a–c) shows field photographs of Cu–Fe–Au vein-type hydrothermal mineralisation in NW-SE faults and fractures in the Bajestan area.
Shallow seismic reflection imaging of the Alpine Fault through late Quaternary sedimentary units at Whataroa, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2021
Aleasha King, Patrick Lepine, Andrew R. Gorman, David J. Prior, Adrienn Lukács, M. Hamish Bowman, Sheng Fan, Andrew Robertson, Franz Lutz, Jennifer D. Eccles, Stefan Buske, Vera Lay, Douglas R. Schmitt, Heather Schijns
A system of reverse faults has been interpreted (Figure 5) and mapped (Figure 6) by identifying offsets in otherwise continuous reflective horizons associated with near surface sedimentary units, in all of the seismic profiles. Note, however, that interpretation of these faults must also consider that the Alpine Fault in this region is expected to have about 3–4 times as much along-strike motion as vertical motion (as mentioned previously). The offset of reflections across a fault will therefore correspond to geological units that have undergone considerable strike-slip – as well as dip-slip – motion.
Assessing Seismic Behavior of a Masonry Historic Building considering Soil-Foundation-Structure Interaction (Case Study of Arge-Tabriz)
Published in International Journal of Architectural Heritage, 2020
Ahmad Fathi, Arjang Sadeghi, M. R. Emami Azadi, Nader Hoveidaie
Based on Code 2800, accelerograms with the following criteria were selected and downloaded from The Pacific Earthquake Engineering Research Center (PEER website): (i) magnitudes of greater than 6 (in Richter scale), (ii) arising from strike-slip faults, (iii) recorded on the soil of type III, and (iv) with strong duration greater than about 10 sec. Selected records which presented in Table 5, are scaled utilizing Seismomatch program for fixed base seismic analysis (SeismoSoft 2016a).