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Significance of in situ stress measurement in the earth science research
Published in Katsuhiko Sugawara, Yuzo Obara, Akira Sato, Rock Stress, 2020
Up to now, the in situ stress measurements were made near the surface, the farther deep measurements should be made, and it is required to study the varying regulation of the magnitude and the direction of principal stress with the increase of the depth. A lot of in situ stress measurements are necessary to be made so that the relationship between the tectonic stress field, the present tectonic activity and earthquake is found. But since the fund is limited and there is variety of restrictions, the measurement will be made at certain region only and the times of the measurements are also lim-ited.Therefore the data of the seismogeological survey, the imitated experiment and others should be considered when the analysis of the tectonic stress field is made. This is the quite important basic research for the studies of crustal stress state and geodynamics, and exploring the reason of the earthquake occurrence, earthquake prediction, and the mode of the present crustal movements.
Magmatism in the Context of the Present-Day Tectonic Settings
Published in O.A. Bogatikov, R.F. Fursenko, G.V. Lazareva, E.A. Miloradovskaya, A. Ya, R.E. Sorkina, Magmatism and Geodynamics Terrestrial Magmatism Throughout the Earth’s History, 2020
O.A. Bogatikov, V.I. Kovalenko, E.V. Sharkov, V.V. Yarmolyuk
As shown above, two stages can be recognized in the development of continental rifts (Grachev, 1987). The early pre-rift stage is characterized by an overall uplift of the area, without a clear relationship between volcanism and rift structure. Eruptions of weakly differentiated lava series, often represented by homogeneous lava flows of moderately alkaline basalts or tholeiites (e.g. the Baikal Rift and the Ethiopian Rift) and in other cases by phonolites (Kenyan Rift), are typical for this stage. As a whole, it resembles a continental flood basalt province. The second stage of continental-rift evolution is marked by more intensive tectonic activity, resulting in the formation of rift basins and mountainous topography. Volcanic activity is limited mainly to the rift basins or takes place within them. A wide spectrum of magma composition characterized this stage, often under the domination of alkaline basalts. Fissured eruptions of weakly differentiated alkaline volcanics were accompanied by the formation of central-type volcanoes responsible for the generation of differentiated rocks.
Earth Systems and Cycles
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Geologists do not agree on the exact number of lithospheric plates. In part, that number depends on whether plates that were once separate, but move as a single unit today, are lumped or split. For example, the boundary between North America and the Atlantic Ocean was once an active subduction zone. Today, however, the North American continent and the Atlantic Ocean, from the east coast of the United States to the Mid-Atlantic Ridge, move together as a single plate (see Fig. 2.24). The two formerly independent plates (North America and the western half of the North Atlantic) are said to be welded together, and the boundary between them is called a passive margin (because no subduction or other tectonic activity is occurring there). Together the two former plates make up most of the present-day North American Plate. Greenland, parts of the Caribbean, a small part of Russia, and a few islands in the Atlantic Ocean are also part of the North American Plate. Today the western edge of the North American Plate is an active margin characterized by subduction and volcanism on the coasts of Washington and Oregon, the San Andreas transform fault in California, and more subduction and volcanism in Mexico. The eastern edge of the North American Plate is an active margin characterized by volcanism and a plate boundary at the Mid-Atlantic Ridge.
A spatial evaluation method for earthquake disaster using optimized BP neural network model
Published in Geomatics, Natural Hazards and Risk, 2023
Hanxu Zhou, Ailan Che, Xianghua Shuai, Yi Zhang
The Lushan Ms7.0 earthquake occurred on April 20, 2013 and the epicentre was located at 30°18’N, 103°56’E, in Lushan County, Sichuan Province, China. The focal depth of the earthquake was 13 km. The affected area was the junction of the Qinghai Tibet Plateau and the Sichuan Basin. The Lushan earthquake was caused by a tectonic activity in the Longmenshan fault zone, similar to the 2008 Ms8.0 Wenchuan earthquake. The distance between the epicentres of the Lushan earthquake and the Wenchuan earthquake was approximately 85 km. A total of 196 people were killed, 21 were missing, and 11470 were injured in the Lushan earthquake. The Lushan earthquake affected an area of 12500 km2 and caused a direct economic loss of approximately 185.4 billion yuan. After the earthquake, the Sichuan Province immediately started first-level emergency procedures and sent out an army to carry out emergency rescue work.
Geological setting of exceptional geological features of the Flinders Ranges
Published in Australian Journal of Earth Sciences, 2020
Many of the granites, especially the Moolawatana Suite, contain minerals exceptionally rich in radiogenic potassium, uranium and thorium, which have been generating radioactive heat since their hosts’ intrusion. This heating effect was enhanced and trapped when insulating strata of the Adelaide Geosyncline were deposited on these basement rocks in the Neoproterozoic and Cambrian, and this resulted in a protracted and possibly unique history of melting, alteration and hydrothermal activity as exhumation progressed throughout the Paleozoic, Mesozoic and Cenozoic. Significantly, it appears that this was achieved without the obvious involvement of crustal magmas. The inherent heating may also have significantly promoted and influenced tectonic activity during the Cambrian Delamerian Orogeny and subsequent uplift. The heating effect persists until the present day as the Paralana Hot Springs. Details are given in following sections.
Mechanism for seismic supershear dynamic rupture based on in-situ stress: a case study of the Palu earthquake in 2018
Published in Geomatics, Natural Hazards and Risk, 2022
Kanghua Zhang, Yishuo Zhou, Yimin Liu, Pu Wang
The Mw7.5 Palu earthquake occurred at the intersection of the Australian, Sunda, and Philippine plates with strong tectonic activity. The geological structure of Sulawesi Island in Indonesia is complex. The basin where Palu City is located is a near-south-north valley formed by the long-term left-lateral strike-slip activity of the Palu-Kolo fault, and active faults have developed in the eastern and western margins of the basin (Bellier et al. 2006). The rupture with left-lateral strike-slip is compatible with normal fault characteristics. The MW7.5 earthquake occurred on 28 September 2018 at 10:02 (UTC); the epicentre was located at 0.178° S, 119.84° E and the hypocentre depth was 13.5 km, as reported by USGS (2020), all FMSs are listed in Supplement II.