| 摘要 |
A calculation window in two parts is selected from a number (n) of detectors. For different levels of seismic energy propagated in the form of surface waves (3, 4) through the soil (12) or subsoil (13) the data are treated in the window. The surface waves travelling from left to right and from right to left are compared to locate any heterogeneities represented by amplitude contrast events The method involves recording and analysing seismic data received using a seismic flute (1) placed on the surface of the ground, with N seismic data detectors (2) spaced over the whole length for a distance (DX). The seismic flute is connected to means of treating the data recorded by all or some of the detectors. To locate the seismic energy amplitude contrasts, the seismic energy levels are calculated for a wave travelling from left to right at the left end and at the right end; for a wave travelling from right to left at the right end and at the left end. Each time the different energy levels recorded in each part is multiplied by the total directed energy. The resulting ratios are compared to each other. The number of detectors (n) in the calculation window is the same as the total number of detectors (N). To increase the viability of the results and allow auscultation on a weak surface, the calculation window of nN detectors is displaced along the flute as many times as possible within the N detectors. Two consecutive calculation windows are spaced by a distance of at least the distance (DX) between two consecutive detectors. To detect heterogeneities in a large surface, in particular along long linear routes, the seismic flute is displaced successively by an amount depending on its length, the number of detectors it includes, the spacing between the detectors , the size of the smallest calculation window desired and the spacing between two calculation windows. Ambient noise, manufactured noise or anthropic noise are used as the seismic energy source.
|
