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Focal M echanisms of M icro-earthquakes in the Little Carpathians - the Influence

AIM S econd A nnual M eeting September, 29.-30., 2011 Prague. Progseis, Ltd. Focal M echanisms of M icro-earthquakes in the Little Carpathians - the Influence of the Model and of the Source Time Function Used. Lucia Fojtíková , Martin G ális a Jiří Zahradník

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Focal M echanisms of M icro-earthquakes in the Little Carpathians - the Influence

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  1. AIMSecond Annual Meeting September, 29.-30., 2011 Prague Progseis, Ltd. Focal Mechanisms of Micro-earthquakes in the Little Carpathians - the Influence of the Model and of the Source Time Function Used LuciaFojtíková, Martin Gális a Jiří Zahradník Geophysical Institute SAS, Bratislava, Slovakia in cooperation with industrial partner: JurajSekereš DagmarSekerešová Progseis, Ltd., Trnava, Slovakia

  2. Outline Introduction Moment Tensor Inversion Using Isola Program Source Time Function Influence of the Model Results Q&A

  3. Area Under Investigation • events out of seismic network (including the strongest one) • complicated geological situation • insufficiently accurate model Model by Geofyzika Brno, 1985

  4. Isola • - waveform inversion • - the Green functions were calculated using the discrete-wave-number method (1D model) • orfinal differences method (3D model) • low frequency content of seismic signal • the match between theobserved and best-fitting synthetic data is characterizedby the overallvariance reduction (VR) Sokos and Zahradník (2009)

  5. Time Function displacement velocity 1Hz 5Hz 1Hz 5Hz 1Hz 5Hz 1Hz 5Hz

  6. Time Function gabor_function(delta-like) 1 Hz

  7. Time Function gabor_function(delta-like) 3 Hz

  8. Time Function gabor_function(delta-like) 5 Hz

  9. Time Function gabor_function(delta-like) 1 Hz gabor_function(delta-like) 3 Hz gabor_function(delta-like) 5 Hz VR = 2.204E-1 VR = 5.64E-1 VR = 4.954E-2 V14, Ml=2.2, h=5.2km

  10. Velocity Models 2.1 low -speed model 4.0 medium - speed model 4.2 high -velocity model A JABO SPAC B PLAVBUKOLAKS DVODHRADKATALANCMODSPVESSMOL C

  11. V14, Ml=2.2, h=5.2km A C A+B+C C–>VR = 2.76E-1 A–>VR = 2.68E-1 A+B+C–>VR=2.99E-01

  12. V14, Ml=2.2, h=5.2km Reference focal mechanism from inversion of amplitudes: A+B+C 3D 3D–>VR=1.81E-01 A+B+C–>VR=2.68E-01

  13. V14, Ml=2.2, h=5.2km -> 4.2km 3D 1-2Hz Reference focal mechanism from inversion of amplitudes: 3D 2Hz–>VR=2.12E-01

  14. V14, Ml=2.2, h=5.2km -> 4.2km 3D 1-3Hz Reference focal mechanism from inversion of amplitudes: 3D 3Hz–>VR=2.45E-01

  15. V03, Ml=3.4, h=10.2km Reference focal mechanism from inversion of amplitudes: A+B+C 3D 3D–>VR=4.17E-01 A+B+C–>VR=5.31E-01

  16. CONCLUSIONS We have analyzed an influence of the time function on the wave form inversion It is important to check corner frequency of the earthquake and choose the appropriate time function Velocity model has a high influence on the inversion Using suitable 1D models individually for each station produced better results than 3D model This is caused by the 3D model not being accurate enough for this area, therefore it is needed to improve the 3D model for Little Carpathians region

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