Moving coil geophone and piezoelectric sensor(including piezoelectric pressure hydrophones used in water and piezoelectric ac-celerometers used on land,LP)are the two most widely employed types of sensors in geophysical prospecting.A table consisting of the physical structures,mathematical models,and transfer functions of these two sensor types is established for comparison.Theoretical analysis and field experiment data showed that the velocity measured by moving coil geophone and the acceleration by LP accelerometer are equiva-lent across the major frequency bands in terms of representing ground movement.Regarding hydrophone,it is essential to understand that it is pressure-type detector,not an accelerometer.Based on the fundamentals of seismic wave dynamics and practical application,output of pressure-type hydrophone is proportional to the velocity of water particles for the up-going wave field and a-180° phase difference is exhib-ited for the down-going wave field.This relationship forms the basic principles for dual-sensor summation technology.This technology relies on several assumptions,such as a plane wave field,the sensor being very close to the seafloor but without direct contact(avoiding sensor-ground coupling effects),and without involvement of the sensing system.The author questions these assumptions and argues that more ef-fective attenuation of water column reverberation by this technology requires additional efforts theoretically,experimentally and operational-ly.Meanwhile,the main function of sensor is simply to follow the movement of the ground faithfully,circuit-based enhancement of high fre-quencies in the field may reduce the S/N ratio and resolution and should not be promoted.Finally,the classification of sensors based on dif-ferent standards has been clarified,contributing to a more thorough understanding of the nature of sensors and also its output data.
国家科技期刊平台
NSTL
维普
万方数据
