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Geomorphology of the Gubbio Basin (Central Italy): understanding the active tectonics and earthquake potential
S. Pucci,P. M. De Martini,D. Pantosti,G. Valensise
Annals of Geophysics , 2003, DOI: 10.4401/ag-3458
Abstract: The Gubbio Basin is a 22 km long, 4 km wide depression located within the North-Central Apennines fold-andthrust belt. The basin is bounded to the east by the Gubbio Fault, a W-dipping, normal fault dissecting a large Jurassic-Oligocene anticline. Although located along one of the main seismogenic zones of the Peninsula, both historical and instrumental is seismicity is limited with the only exception for the 29 April 1984, Ms 5.3 earthquake, which occurred about 10 km southwest of the basin. Most of the literature attributes this seismicity to the Gubbio Fault. New geomorphic and geologic investigations based on field and aerial photo surveys and DEM analyses provide new insights on the active faulting in the area and are used to infer potential seismogenic sources. Limited evidence of ongoing deformation along the surface expression of the Gubbio Fault was found, possibly because of low rates of deformation versus fast erosional processes. The western side of the basin appears to be controlled by an east-dipping normal fault, antithetic to the Gubbio Fault. Standard dislocation modeling was used to understand the role played by the Gubbio Fault and its antithetic. The Gubbio Fault was divided into a high-angle section above 3.5 km and a low-angle section between 3.5 and 6 km depth. Based on different tests we conclude that both sections of the Gubbio Fault as well as the antitethic fault contributed to the present setting of the basin. At present the antithetic fault appears to be the most effective in producing a geomorphic signature and controlling the basin width. The high-angle Gubbio Fault played a major role in the basin growth but now its activity rate appears minor. Because of the characteristics and location of the 1984 earthquake, the low-angle Gubbio Fault is assumed to be presently active and seismogenic. Based on the integration of geologic, geomorphic and seismological data we suggest that the low-angle Gubbio Fault is formed by two individual sources capable of M 5.3-5.9 earthquakes. The southern source ruptured in the 1984 earthquake while the northern source did not rupture recently nor historically.
Active tectonics along the submarine slope of south-eastern Sicily and the source of the 11 January 1693 earthquake and tsunami
A. Argnani, A. Armigliato, G. Pagnoni, F. Zaniboni, S. Tinti,C. Bonazzi
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2012,
Abstract: South-eastern Sicily has been affected by large historical earthquakes, including the 11 January 1693 earthquake, considered the largest magnitude earthquake in the history of Italy (Mw = 7.4). This earthquake was accompanied by a large tsunami (tsunami magnitude 2.3 in the Murty-Loomis scale adopted in the Italian tsunami catalogue by Tinti et al., 2004), suggesting a source in the near offshore. The fault system of the eastern Sicily slope is characterised by NNW–SSE-trending east-dipping extensional faults active in the Quaternary. The geometry of a fault that appears currently active has been derived from the interpretation of seismic data, and has been used for modelling the tsunamigenic source. Synthetic tide-gauge records from modelling this fault source indicate that the first tsunami wave polarity is negative (sea retreat) in almost all the coastal nodes of eastern Sicily, in agreement with historical observations. The outcomes of the numerical simulations also indicate that the coastal stretch running from Catania to Siracusa suffered the strongest tsunami impact, and that the highest tsunami waves occurred in Augusta, aslo in agreement with the historical accounts. A large-size submarine slide (almost 5 km3) has also been identified along the slope, affecting the footwall of the active fault. Modelling indicates that this slide gives non-negligible tsunami signals along the coast; though not enough to match the historical observations for the 1693 tsunami event. The earthquake alone or a combination of earthquake faulting and slide can possibly account for the large run up waves reported for the 11 January 1693 event.
Tectonic caves of Solai in the Kenyan Rift Valley  [PDF]
Robert A. Davis
International Journal of Speleology , 1998,
Abstract: Tectonic caves al Solai, Kenya, were explored in 1970. These lie in a complex geological area of the Great Rift Valley in columnar-faulted ignimbrite. Fissures are presumed to have been widened by later tectonic activity -e.g. the major earthquake of January, 1928. The caves and exploration are briefly described. Questions of formation, drainage and possibilities of steam reservoirs are discussed.
Characteristics of the crustal structure and hypocentral tectonics in the epicentral area of Nan’ao earthquake (M7.5), the northeastern South China Sea
Huilong Xu,Xuelin Qiu,Minghui Zhao,Jinlong Sun,Junjiang Zhu
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-9095-x
Abstract: 1918 Nan’ao earthquake (M7.5) occurred in the northeast coastal areas of Guangdong Province. With the seismogeological survey of the epicentral area and history materials analyses, the earthquake epicenter was estimated to locate in the intersection part of the Binhai fault zone (Littoral) and Huanggangshui fault, which strikes NEE and NW, respectively. The activities of the NEE-striking thrust fault and NW-striking extensional fault that were attributed to 1918 Nan’ao earthquake occurred in the Dongshan Island of the epicentral area; they reflected the focal stress field with compression in NW-SE direction and extension in NE-SW direction. The isoseismal contour of seismic intensity X shows a shape of ‘X’ composed of two mutually overlapping ellipses with two axes striking NEE and NW, respectively, and such shape implies that the occurrence of this earthquake is controlled by a pair of conjugate seismotectonic faults constituted by the NEE-striking Binhai fault zone and the NW-striking Huanggangshui fault. The Binhai fault zone is a dominant seismogenic structure, and the NW-striking Huanggangshui fault is the subdominant one. The onshore-offshore deep seismic profile that crossed the epicentral area and was perpendicular to the strike of the Binhai fault zone was obtained. According to the analyses of the seismic data, the Binhai fault zone is defined as a low velocity zone with SE dip-slip in the crustal structure section. The Binhai fault zone is a boundary fault between the South China subplate and South China Sea subplate. The crust structure on the northwest side of Binhai fault zone is a normal continental crust with a thickness of 30 km, and the one on the southeast side of the fault zone is a thinning continental crust with a thickness of 25–28 km. The Binhai fault zone is an important seismogenic fault and also is an earthquake-controlling fault. The intersection part between the Binhai fault zone and the low velocity zone of upper crust is advantageous to stress concentration and strain energy accumulation, and presents the deep dynamic conditions for the earthquake’s pregnancy and occurrence.
Radon in Caves.
Cigna Arrigo A.
International Journal of Speleology , 2005,
Abstract: The physical characteristics of radon are reported as well as its sources,the transport in rock and its behaviour in caves. Then,the instruments,both active and passive, used for the measurement of radon concentration are discussed by taking into accounttheir respective advantages and disadvantages for the use in the cave environment. Since in many countries radon is the objectof regulations that were adopted for radiation protection purposes, this aspect is examined and the recommendations issued byinternational organisations and enforced in different countries are reported. Materials, methods and other remarks on the limitsimplementation are also listed with the aim of providing the managers of show caves with some instruments to comply with thedomestic requirements with the most convenient solution.
Seismic Crystals And Earthquake Shield Application  [PDF]
B. Baykant Alagoz,Serkan Alagoz
Physics , 2009,
Abstract: We theoretically demonstrate that earthquake shield made of seismic crystal can damp down surface waves, which are the most destructive type for constructions. In the paper, seismic crystal is introduced in aspect of band gaps (Stop band) and some design concepts for earthquake and tsunami shielding were discussed in theoretical manner. We observed in our FDTD based 2D elastic wave simulations that proposed earthquake shield could provide about 0.5 reductions in magnitude of surface wave on the Richter scale. This reduction rate in magnitude can considerably reduce destructions in the case of earthquake.
Clouds in caves
Speleogenesis and Evolution of Karst Aquifers , 2004,
Abstract: This paper considers the different processes that can create vapour pressure above the equilibrium in the cave atmosphere: ascending air parcels, pressure drop behind bottlenecks, mixing of saturated air parcels at different temperatures and water flow fragmentation. These processes are essentially the same as those leading to clouds forming in the open atmosphere, always connected with air movements. The difference of adiabatic lapse rates of water and moist air creates temperature imbalance between the flowing fluids in deep underground systems, leading to thermal and water exchanges, in which water flow globally subtracts energy from the system. The high purity of caves atmospheres tends to delay condensation. Condensation is concentrated where airflows are in close contact to the cave wall. The rate of aggressive water condensation on the walls is comparable to the external rain and can play a leading role in Speleogenesis.
Pathogenic and opportunistic microorganisms in caves  [PDF]
Jurado Valme,Laiz Leonila,Rodriguez-Nava Veronica,Boiron Patrick
International Journal of Speleology , 2010,
Abstract: With today’s leisure tourism, the frequency of visits to many caves makes it necessary to know about possible potentially pathogenic microorganisms in caves, determine their reservoirs, and inform the public about the consequences of such visits. Our data reveal that caves could be a potential danger to visitors because of the presence of opportunistic microorganisms, whose existence and possible development in humans is currently unknown.
Is it always dark in caves?
Badino Giovanni
International Journal of Speleology , 2000,
Abstract: Underground natural sources of visible light are considered. The main light producer is Cerenkov radiation emitted in air, water and rock by cosmic ray muons, that depends, in a complex way, on shape of mountain and of caves. In general the illumination increases linearly with the cavity dimensions. Other light sources are from secondary processes generated by radioactive decays in rock from minerals luminescence. The natural light fluxes in caves are in general easy to detect but are not used from underground life.
Caves and Karsts of Northeast Africa.  [PDF]
Halliday William R.
International Journal of Speleology , 2003,
Abstract: At least potentially karstifiable rocks cover much of the surface of Egypt and northern Libya. Study of caves and other karstic features of this region has been hampered by lack of roads, rapid disintegration of the surface of friable, poorly consolidated limestone, wind-blown sand and other factors. Interbedding with marly aquicludes hampers speleogenesis locally. Calcareous and evaporite karsts are present, however, and their waters are important albeit generally limited resources. Large quantities of fresh water are lost through submarine springs downslope from Libya’s Gebel al Akhdar range; the caves and karst of that range may be among the world’s greatest. A recent attempted compendium of caves and karsts of Egypt and Libya contains several important errors; the supposed 5+ km Ain Zayanah Cave does not exist and the Zayanah System includes several smaller caves. The Bir al Ghanam gypsum karst of northwest Libya, however, has caves up to 3.5 km long. In Egypt, the Mokattam, South Galala, Ma’aza, Siwa and Western Desert karsts and the “White Desert” chalk karst of Farafra Depression are especially important. Qattara and nearby depressions may be karstic rather than structural in origin. Unique Wadi Sannur Cave is the world’s largest gour and a potential World Heritage site. Little knownsandstone karsts or pseudokarsts in southwestern Egypt may contain analogues of features recently identified on Mars. The well-publicised Uweinat caves of northwestern Sudan are talus caves.
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