  Understanding the causes of sinkholes and determining the earth's subsurface
properties will help Engineering Geologists in designing and constructing
different kinds of structures. Also, determining subsurface properties will
increase possibilities of preventing expensive structural damages as well as a
loss of life. Among the available health monitoring techniques, non-destructive
methods play an important role. Full-waveform inversion together with the
Gauss-Newton method, which we called as the regular method, able to determine
the properties of the subsurface data from seismic data. However, one of the
drawbacks of the Gauss-Newton method is a large memory requirement to store the
Jacobian matrix. In this work, we use a different cell size approach to address
the above issue. Results are validated for a synthetic model with an embedded
air-filled void and compared with the regular method.
