Focal Mechanism by ISNet

Last Update by Vassallo M. on May 23, 2012

The focal mechanism is computed using the code FMNEAREG (Focal Mechanism from NEAr source to REGional distance records; Delouis et al., 2008). For the inversion we used the ISNet acceleration records that are integrated twice and band-pass filtered in a range that is automatically selected for each component of the seismogram.
The filtered displacement recordings are inverted to find the parameters of the focal mechanism using a two-step grid search. In the first step, the minima of the normalized rms error between the observed data and the synthetics are searched using a coarse grid, while in the second step the search is performed in a finer grid around the minima previously identified.
For each tested triplet (strike, dip, rake), the parameters of the point sources (amplitudes of the elementary triangular functions, rupture onset time, and rake) are determined through a simulated annealing algorithm.

Delouis, B., C. Charlety, and M. Vallee (2008). Fast determination of earthquake source parameters from strong motion records: Mw , focal mechanism, and slip distribution, in EGU General Assembly, Geophys. Res. Abstr. 10, abstract 04939.

Comparison between computed and observed waveforms

Posted by Vassallo M.