1,721,018 research outputs found
Tectonic deformation events and local seismicity in the Gran Sasso area of the central Apennines
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A 2-D model for tilt and strain fields associated to earthquakes in crustal block structures
No full textA 2-D model for slow crustal movements, including tilt and strain anomalies before earthquakes as well as shape and time lag of each preseismic anomaly with respect to the time of origin of the corresponding earthquake, is proposed. The model represents a numerical study to evaluate the behavior of a series of crustal rigid blocks separated by narrow fault zones filled with viscoelastic material. Rheology of the fault material is described by constitutive equations of standard linear solid. Vertical displacement and rotation of the blocks result from the vertical uplift of one (central) block due to a vertical Force. Displacements and tilts of blocks are computed from a system of linear differential equations which are solved numerically. The main characteristic feature of the model is that the viscoelastic parameters of the fault zone, where fracture occurs (at the boundary of the rising block), may change in time? simulating the earthquake preparation. Numerical modelling shows that tilt behavior at successive blocks reveals anomalies which are similar in shape to the observed ones. The anomalies are of opposite signs in adjacent blocks, and show a time lag with distance from the fracturing zone. (C) 1998 Elsevier Science B.V
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Anomalie elettromagnetiche, sismoacustiche e di livello di acqua rilevate nella grotta Amare (Gran Sasso, L' Aquila) in occasione di due terremoti locali
No full textNormal and anomalous behaviour of electric, magnetic and seismoacoustic signals recorded in the Amare cave
No full textSince 1987 multichannel instrumentation has been recording electromagnetic and seismoacoustic emissions in the Amare cave (Gran Sasso - L'Aquila). Equipment detecting RMC (Principality of Monaco) longwave broadcasting (216 kHz) has been operating in the same place. Data collected during this period have pointed out two different phenomena called «quiet» and «perturbed» that characterize the normal behaviour of the cave. On 25 August 1992 an earthquake with M = 3.9 occurred in the Gran Sasso area and on 4 June 1993 an earthquake with M = 4.3 occurred in Umbria, 100 km to north of the Amare cave. Before these earthquakes, electromagnetic, seismoacoustic, and RMC data showed anomalies. Here we present the observed phenomenology and discuss the possibility that the anomalies can be considered precursors of the earthquakes
Artificial and natural electro-magnetic signals revealed during two years in the Amare cave (Central Italy)
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