- © 2013 by the Seismological Society of America
Online Material: Additional figures.
Focal mechanism and moment tensor determinations based on regional and local waveforms have become routine tasks in seismology. In recent years, considerable effort has been dedicated to extend software capabilities, in particular towards the inclusion of finite‐extent sources and easy, user‐friendly use. Two examples of these efforts are the FMNEAREG and KIWI software packages. Focal Mechanism from NEAr source to REGional distance records (FMNEAREG; Delouis et al., 2008; Maercklin et al., 2011) performs a grid search in order to find pure double‐couple sources, based on a 1D (line) finite‐source representation and complete elastodynamic wave field. The KIWI software (KInematic Waveform Inversion; Cesca et al., 2010) allows the automatic retrieval of point‐source parameters, and for magnitudes above a given threshold kinematic finite‐fault rupture models can also be obtained. KIWI relies on a pre‐calculated database of Green’s functions. KIWI performs the moment tensor inversion in two steps, the first of which is based on the fit of amplitude spectra. The second step is based on time‐domain waveform fits.
The ISOLA, ISOLated Asperities, software package (Sokos and Zahradník, 2008) also performs waveform inversions to find source parameters. ISOLA is based on FORTRAN codes and offers a user‐friendly MATLAB graphical interface (GUI; www.mathworks.com/products/MATLAB). ISOLA allows for both single‐ and multiple‐point‐source iterative deconvolution (Kikuchi and Kanamori, 1991) inversion of complete regional and local waveforms. The moment tensor is retrieved through a least squares inversion, whereas the position and origin time of the point sources are grid searched. The computation options include inversion to retrieve the full moment tensor (MT), deviatoric MT, and pure double‐couple MT. Finite‐extent source inversions may also be performed by prescribing a priori the double‐couple mechanism (which will remain homogeneous over the fault plane). Green’s functions, including near‐field terms, are calculated using the discrete wavenumber method (Bouchon, …