Very Shallow Seismic Reflection Profiling Using Portable Vibrator

A portable, high frequency vibrator system has been developed to effectively increase seismic resolution.<br>The vibrator is based on the principles of electrodynamics. A 65 kg magnet serves as the reaction mass, no external<br>hold down force is applied. Two persons can easily move the light-weight vibrator in the field. Amplitude and phase<br>of the vibrator sweep are controlled by a multipurpose data acquisition system.<br>Several experiments to test the performance of the vibrator as a seismic source have been carried out. This<br>paper describes results of two of these tests. The first experiment was conducted on an embankment that consists of<br>gravelly soil underlain by an alluvial silty clay and a diluvial clayey silt. Distinct reflecting interfaces of these layers<br>were clearly mapped to a depth of 50 m. The second experiment was conducted at an OYO test site where pieces of<br>styrcne foam hav.e been buried at known depths ( 0.5 m -2 m) below pavement. Using the portable vibrator system,<br>diffraction events from the styrene foam at depths of 1.5 m and 2.0 m were detected.<br>Results of these experiments indicate that the portable vibrator is a promising seismic source for high<br>resolution seismic reflection profiling.