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Survey Line (survey + line)

Distribution by Scientific Domains

Earth and Environmental Science	50%

Selected Abstracts

Finding the strike direction of fractures using GPR

GEOPHYSICAL PROSPECTING, Issue 3 2001
Soon Jee Seol
GPR reflection energy varies with antenna orientation relative to the strike and dip of the reflector. This directional dependence of GPR responses was investigated through numerical experiments and was used to estimate the azimuth of fractures and joints. Three antenna configurations were considered in this study: perpendicular-broadside (YY mode), parallel-broadside (XX mode) and cross-polarization (YX mode). The reflection energy in the cross-polarization mode shows a shape characteristic similar to the strike, regardless of the dip angle. Those in the other two modes show quite different amplitudes from the strike, depending on the dip angle. We have developed a strike-direction-finding scheme using data obtained from the three different modes for the same survey line. The azimuth angle of each reflector was displayed in colour on the GPR profile. This scheme was applied to a field survey at a granite quarry in southern Korea. The GPR profiles showed different images of the reflectors depending on the antenna configuration. The estimated azimuths of reflectors obtained using our scheme matched fairly well with those of known fractures and joints. [source]

Birds on edge: avian assemblages along forest-agricultural boundaries of central Victoria, Australia

ANIMAL CONSERVATION, Issue 2 2001
Monica J. Campi
Habitat clearance generally produces fragmented landscapes. A major consequence is the creation of large amounts of new ,edge habitat', often of a kind not previously existing, such as abrupt forest- agricultural land interfaces. Much work from around the world suggests that proliferation of edge habitat seriously affects birds reliant on large forest blocks to persist, and the intrusion of edge specialists into areas they did not previously occupy. These processes often generate avifaunal gradients in which assemblages change from the interior to the edge. This effect is explored in the largest remnant block of box-ironbark forest of central Victoria, Australia (about 30,000 ha). Eight radially oriented survey lines were established around the periphery of the block. Along each survey line, five transects with long axes oriented parallel to the edge were positioned with midlines at 40 m, 160 m, 280 m and 400 m into the forest, and one transect 80 m into the agricultural land, yielding a total of 40 transects. Six identical transects were located deep within the forest (> 2 km). There was little evidence of a change in the avifauna from interior to edge, although mean richness was depressed in the edge habitats compared with forest interior transects. These results were essentially the same for ,all species' or ,forest dependent' species. Thus, there is little evidence for marked edge effects on the avifauna of these large forest blocks, although work in intermediate sized remnants (100-1000 ha) is needed to identify thresholds at which edge effects begin to be manifested. [source]

GPR survey to understand the stratigraphy of the Roman Ships archaeological site (Pisa, Italy)

ARCHAEOLOGICAL PROSPECTION, Issue 1 2003
M. T. Carrozzo
Abstract Two surveys with ground-penetrating radar (GPR) were carried out in June and December 2000 at the Roman Ships archaeological site (Pisa, Italy). Both surveys were undertaken at selected locations, placed on the plan of excavation (,5 m from the ground surface), using a GSSI Sir System2 incorporating 35, 100, 200 and 500 MHz centre-frequency antennae. The main purpose of the two surveys was to test the value of radar in respect of penetration depth and, therefore, to reconstruct the geological stratigraphy, given the general not too favourable site conditions. The results showed that most of the GPR data acquired with the 35 MHz antenna were contaminated by strong reflections caused by above-ground objects near the survey lines. In fact, the archaeological area is protected on every side by iron barriers, around 6 m high, in order to guarantee the stability of the walls and to contain the present shallow groundwater. Therefore, it is very important to recognize the reflections through air (surface scattering) and not to confuse them with the reflections from underground geological features. For this purpose higher frequency antennae, less prone to surface scattering problems, although allowing shallower penetration depths, also have been used. Their higher resolution permitted the identification of some anomalies probably related to shallow stratigraphical boundaries, as well as other anomalies probably attributable to archaeological features. Moreover, the numerous measurements carried out in the second survey to estimate the velocity of propagation of the electromagnetic waves in the ground, contributed to a better interpretation of the geology of the site. Copyright © 2003 John Wiley & Sons, Ltd. [source]