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The geological origin of building stones
Published in John A. Hudson†, John W. Cosgrove, Understanding Building Stones and Stone Buildings, 2019
John A. Hudson†, John W. Cosgrove
During the movement of the Earth’s tectonic plates, subduction can occur, i.e., one plate can be forced beneath another, see the subduction zones at the convergent plate margins in Figure 2.6. The subducting plate is heated up and begins to melt, producing large volumes of magma which can be injected into the overlying rocks where it either cools slowly at depths as granite masses or cools quickly as a result of extrusion at the Earth’s surface as a volcano. These granite masses and volcanoes form along the line of the mountain belt, i.e., parallel to the boundary between the two converging plates. Two such chains of granites, linked to ancient collisions between plates, can be seen in Figure 2.11. One runs NE–SW from John O’Groats SW into Northern Ireland. This is linked to the closing of an ancient ocean, the Iapetus ocean, which occurred in the Palaeozoic Era during the Cambrian and Ordovician periods ~500–450 million years ago, and which produced the Caledonian mountain belt.
Seismic hazard analysis: An overview
Published in Mariana R. Correia, Paulo B. Lourenço, Humberto Varum, Seismic Retrofitting: Learning from Vernacular Architecture, 2015
J.F.B.D. Fonseca, S.P. Vilanova
Earthquakes are not randomly distributed in space. The Earth’ crust is composed of large tectonic plates that move slowly on top of the molten rocks that lay underneath, and the earthquakes concentrate in the boundaries were the plates collide, spread or slide against each other. Plate tectonics, derived in the 1960’s and now observed directly through satellite geodesy, provides a rationale for most of the planet’s seismicity. The strongest earthquakes (magnitudes 8.5 and above) occur at subduction zones, where oceanic plates dive underneath less dense continental crust. This process is taking place around the Pacific Ocean, leading to strong earthquakes in Japan, Chile and Alaska, for instance. In the Indian Ocean, Java and Sumatra (Indonesia) are also the locus of strong subduction earthquakes. Regions of continent-continent collision are also prone to large earthquakes, typically in the magnitude range 7–8.5. These plate boundaries are broader, with the deformation spreading over a belt that can reach ∼1000 km in width. Examples are the continental collision of India with the Eurasian plate. Transcurrent plate boundaries (transformfaults) where tectonic plates slide past each other, such as the San Andreas Fault or the North Anatolian Fault, generate maximum earthquakes in the range 7–8.
Applications of GNSS
Published in Basudeb Bhatta, Global Navigation Satellite Systems, 2021
The earth’s lithosphere is broken up into several tectonic plates—there are seven major and many minor plates (Figure 10.14). These plates move in relation to one another at a very slow rate. The use of very accurate positioning (a few millimetres) allows observation of slow-motion movements of tectonic plates over long periods. Tectonic plates are moving at a few centimetres per year; and a long-term analysis of static receivers allows the movement of plates to be precisely determined. This information can help in earthquake prediction (Aydan 2006; Kato et al. 1998; Jiang et al. 2007). The same applies to studies concerning, for example, the impact of tides on the earth’s surface.
Numerical modeling for the engineering analysis of rock mass behaviour due to sequential enlargement of Lowari tunnel Chitral Khyber Pakhtunkhwa, Pakistan
Published in International Journal of Geotechnical Engineering, 2019
Zahid Ur Rehman, Noor Mohammad, Sajjad Hussain, Muhammad Tahir
Lowari tunnel is positioned in area belonging to the geological formation of the Kohistan Complex which is positioned in between the Eurasian Continental and Indian Plates. It comprises the Kohistan Batholith (intrusive rock) and volcanic sedimentary groups which usually show more or less influence of metamorphism. Due to movements between the tectonic plates regional deformations like faulting and thrusting have occurred. Because of on-going movement of the tectonic plates, this area has to be considered as an active seismic zone.