ISSN:
1573-157X
Keywords:
infinite-space synthetics
;
inversion of near-source data
;
near-field seismograms
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract We have implemented and tested a simple inversionscheme to retrieve source parameters of small andmoderate earthquakes recorded at close distances. Theinversion assumes that such events may be approximatedby a point-source shear dislocation, and the mediummay be considered an infinite space. Theoreticalseismograms used in the inversion include near- andintermediate-field contributions. The effect of freesurface is approximately taken into account bymultiplying the infinite-space synthetics by two. Thelocation of the event is assumed to be known. Based onan examination of the data, the user chooses thelength of the record and the weight of each trace tobe used in the inversion. The shape of the source-timefunction is estimated from the observed seismograms.A grid search is performed to determine the focalmechanism and the seismic moment which minimizes theerror between the observed and the syntheticseismograms. For two or more recordings, the inversiongives a solution which is consistent with thefirst-motion data and/or the moment tensor inversionof regional seismic waves. If only a singlethree-component recording is available then theinversion yields more than one equally acceptablefocal mechanisms. In such cases, the first-motionpolarities or a prior knowledge of the tectonics ofthe region is essential to constrain the solution. Thetest of the method on near-source broadband recordingsof small and moderate earthquakes in Mexico and theaftershock sequence of 1997 Umbria-Marche, Italy showsthat it gives fast, and surprisingly robust andreliable estimation of source parameters.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1009849819475
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