Improving the local wavenumber method by automatic DEXP transformation

• We present a new method for source parameter estimation, based on the local wavenumber (LWN) function.
• We make use of the stable properties of the Depth from EXtreme Points (DEXP) method.
• The depth to source is estimated at extreme points of the LWN scaled by a power-law independent of the structural index.
• The method results particularly suited to deal with high-order LWN.
• The Local Wavenumber DEXP transformation is fully automatic and may be implemented as a very fast imaging method.

In this paper we present a new method for source parameter estimation, based on the local wavenumber function. We make use of the stable properties of the Depth from EXtreme Points (DEXP) method, in which the depth to the source is determined at the extreme points of the field scaled with a power-law of the altitude. Thus the method results particularly suited to deal with local wavenumber of high-order, as it is able to overcome its known instability caused by the use of high-order derivatives. The DEXP transformation enjoys a relevant feature when applied to the local wavenumber function: the scaling-law is in fact independent of the structural index. So, differently from the DEXP transformation applied directly to potential fields, the Local Wavenumber DEXP transformation is fully automatic and may be implemented as a very fast imaging method, mapping every kind of source at the correct depth. Also the simultaneous presence of sources with different homogeneity degree can be easily and correctly treated. The method was applied to synthetic and real examples from Bulgaria and Italy and the results agree well with known information about the causative sources.