Smoothing the source time function – a tool to soften inadequate modelling of the medium during inversion of local waveforms?
Authors: Jechumtálová, Z.; Šílený, J.
Source: Journal of Seismology, Volume 2, Number 2, June 1998 , pp. 145-158(14)
Abstract:The inconsistency of records of local earthquakes and synthetic seismograms due to noise contamination of the data and/or to improper Green function because of an inexact structural model often results in high frequency oscillations of the source time function, which prolongs it spuriously. A priori limit on the roughness of the source time function turned out to reduce the spurious oscillations but it keeps its spurious extension unchanged. Thus, it may yield a severe distortion of the seismic moment. However, it reduces the spurious volumetric component of the mechanism resulting from improper modelling of the structure and, thus, may help decide whether the retrieved volumetric component is real or false. The demand for the smoothness is incorporated as a penalty function in the minimization of the least square residuals, which allows us to decide about the degree of the smoothness. The minimization is performed with a simple genetic algorithm, which offers the advantage of a detailed exploration of the model space reducing the danger of being trapped in local minima.
Document Type: Regular Paper
Affiliations: Geophysical Institute, Acad. Sci. Czech Rep., Boční II/1401, 14131 Praha 4, Czech Republic
Publication date: June 1, 1998