ISSN:
1365-246X
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
Notes:
In 1982/83 the Moroccan and Spanish authorities jointly established a geodetic network spanning the Strait of Gibraltar. In 1984 the network, comprising four stations on the Moroccan and four on the Spanish shore, was observed for horizontal and vertical angles, distances by EDM, levelling, and for astronomical latitudes, longitudes, and azimuths. In 1989 the network was expanded to include a further six stations in Spain, and one in Ceuta, and the whole was observed by GPS using a set of eight receivers.The observational data used proved adequate to determine significant horizontal homogeneous strain, but less apt for vertical deformation. The strain results are given with accuracies of 1 standard deviation (‘tensor’ values for shear): dilatation rate −(0.07 ± 0.04) 10-6yr-1(i.e. diminution of surface area; only determinable if the EDM and GPS length-scales are held to be comparable); shear strain rate (0.12 ± 0.04) 10-6rad y-1; and axis of maximum relative shortening 87°/267°±8° (determinable from changes in shape of the network, and largely independent of the comparability of length-scales).With only eight stations involved in the repeated observations, the results could be influenced by local effects at one or two stations. However, they demonstrate the capability of EDM and GPS observations to detect crustal strain within a period of 5 yr to an accuracy of the order of 0.05 × 10-6rad yr-1.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-246X.1992.tb00585.x
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