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The Geosphere and Geochemistry
Published in Stanley E. Manahan, Environmental Chemistry, 2022
The boundaries between the tectonic plates are where most geological activity such as earthquakes and volcanic activity occur. These boundaries are part of the tectonic cycle and are of the three following types: Divergent boundaries where the plates are moving away from each other. Occurring on ocean floors, these are regions in which hot magma flows upward and cools to produce new solid lithosphere. This new solid material creates ocean ridges.Convergent boundaries where plates move toward each other. One plate may be pushed beneath the other in a subduction zone in which matter is buried in the asthenosphere and eventually remelted to form new magma. When this does not occur, the lithosphere is pushed up to form mountain ranges along a collision boundary.Transform fault boundaries in which two plates slide past each other. These boundaries create faults that result in earthquakes.
Historical Note on Earthquakes
Published in Santiago Pujol, Ayhan Irfanoglu, Aishwarya Puranam, Drift-Driven Design of Buildings, 2022
Santiago Pujol, Ayhan Irfanoglu, Aishwarya Puranam
Major lithospheric plates and their boundaries are shown in Figure 17.10. The arrows in Figure 17.10 indicate the direction of movement at the boundaries. We note that at the mid-ocean ridges the plates move away from one another (divergent or extensional boundaries). At convergent boundaries that are typically associated with deep ocean trenches, the plates move toward one another and one plate bends and cuts into the asthenosphere (subduction). Boundaries where the adjoining plates move past one another are referred to as transform faults.
Bathymetry: Features and Hypsography
Published in Yeqiao Wang, Coastal and Marine Environments, 2020
Heidi M. Dierssen, Albert E. Theberge
Comprehension of the significance and inter-relationships of the primary and secondary features of the seafloor has come about only since the formulation of the theory of plate tectonics. Plate tectonics describes the surface of the Earth in terms of numerous plates that either move away from each other at divergent plate boundaries, collide at convergent plate boundaries, or slide past each other along great faults known as transform faults. The median valleys of mid-oceanic ridges are the primary location of divergent boundaries, also known as seafloor spreading centers, where new seafloor is being produced from upwelling magma. Sites where plates collide with one plate being thrust under another consuming the seafloor, known as subduction zones, are marked by the great oceanic trenches, while colliding plates with no subduction form the great terrestrial mountain ranges of the world such as the Alpine- Himalayan belt of Europe and Asia. Sites where plates slide past one another are marked primarily by the numerous offsets on the mid-oceanic ridge system and are known as transform faults or fracture zones.
Past large earthquakes on the Alpine Fault: paleoseismological progress and future directions
Published in New Zealand Journal of Geology and Geophysics, 2018
Jamie D. Howarth, Ursula A. Cochran, Robert M. Langridge, Kate Clark, Sean J. Fitzsimons, Kelvin Berryman, Pilar Villamor, Delia T. Strong
The Alpine Fault is a transform plate boundary structure that has not produced a large earthquake during the c. 170-yr period of European settlement in New Zealand. This is despite the fault accommodating up to 80% of the boundary-parallel motion between the Pacific and Australian plates, which are moving obliquely past each other at 39 mm/yr in the central South Island (Norris and Cooper 2001, 2007; Wallace et al. 2007). Transform faults accommodating similar amounts of strain, such as the North Anatolian and San Andreas faults, show that such structures are capable of producing large (MW ≥ 7) or even great (MW ≥ 8) earthquakes that pose a significant hazard to society. In the absence of long historical records, knowledge of large earthquake recurrence behaviour can only be derived from paleoseismic investigations (McCalpin and Nelson 2009).