Receivers for MASW Surveys

A receiver in seismic survey senses ground vibration and converts it into electric
current.  The most common type of receiver traditionally used in exploration seismic
surveys is the geophone, which senses the ground vibration through a mass-spring
system enclosed in a magnet as illustrated in a figure on the right. The frequency-
amplitude relationship of a geophone is called "response curve," and is determined
mainly by the size of hanging mass and stiffness of the spring.  

The low-frequency side of the curve is more specifically defined than the high-
frequency side, which usually is open with a gradual attenuation in response.  In this
sense, a geophone acts as a low-cut filter from input-output perspective.  Geophone
frequency represents this “cut frequency” (e.g., 4.5-Hz), which is not sharply defined
but tapers down within a relatively narrow frequency band near this frequency as
shown in two response curves in the figure.  

The lowest (longest) frequency (wavelength) of surface wave a geophone can detect,
therefore, is directly related to this "geophone frequency" as explained in the the
figure below.
There are "vertical" and "horizontal" geophones depending on the sensing
orientation of the mass-spring system.  Horizontal geophones are commonly
used for shear-wave (reflection and refraction) surveys with either transverse
or longitudinal orientation (see figure below).  

"Vertical" geophones are used for MASW surveys.