Generating interface wave using electromagnetic induction source

Abstract

The interface wave is known as a useful tool to study geoacoustic properties and can be conventionally generated by setting up an explosive or a pneumatic source on/above the seafloor. This type of source, however, also excites strong compressional waves in the water and sediment, and so the generated interface wave is affected by this compressional wave, resulting in difficulty in processing. The waves generated in this way are also poor in duality and those sources may cause environmental problems. To solve this, we tried to utilize an electromagnetic induction source, called Boomer, which is generally used in the water as a source for generating compressional waves. First, we fabricated a Boomer with several types of vibrator plates on a small scale. To evaluate the performance of the source, the sound pressure level exited by the source was measured in a water tank and was compared with a designed one. Then we drove the source with the vibrator plates on the seafloor and evaluated the properties of the generated interface wave, which observed by a geophone, and compared the measured wave signal with one generated by dropping a weight. Consequently, the electromagnetic induction source turns out to be useful for generating an interface wave having repeatability.