Focal Mechanisms of Micro-earthquakes in the Little Carpathians - the Influence of the Model and of the Source Time Function Used AIM Second Annual Meeting September, , 2011 Prague Lucia Fojtíková, Martin Gális a Jiří Zahradník Geophysical Institute SAS, Bratislava, Slovakia in cooperation with industrial partner: Juraj Sekereš Dagmar Sekerešová Progseis, Ltd., Trnava, Slovakia Progseis, Ltd.

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

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

Isola Sokos and Zahradník (2009) - waveform inversion - the Green functions were calculated using the discrete-wave-number method (1D model) or final differences method (3D model) - low frequency content of seismic signal - the match between the observed and best-fitting synthetic data is characterized by the overall variance reduction (VR)

Time Function displacementvelocity 1Hz5Hz 1Hz5Hz 1Hz5Hz 1Hz5Hz

Time Function gabor_function (delta-like) 1 Hz

Time Function gabor_function (delta-like) 3 Hz

Time Function gabor_function (delta-like) 5 Hz

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

Velocity Models low - speed model high - velocity model medium - speed model JABO SPAC DVOD HRAD KATA LANC MODS PVES SMOL PLAV BUKO LAKS A B C

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

V14, Ml=2.2, h=5.2km station azimuth [°] distance [km] SMO BUK KAT SPA A+B+CA+B+C A+B+C–>VR=2.68E-01 3D3D 3D–>VR=1.81E-01 Reference focal mechanism from inversion of amplitudes:

V14, Ml=2.2, h=5.2km -> 4.2km 3D 2Hz–>VR=2.12E-01 Reference focal mechanism from inversion of amplitudes: station azimuth [°] distance [km] SMO BUK KAT SPA D 1-2Hz

V14, Ml=2.2, h=5.2km -> 4.2km 3D 3Hz–>VR=2.45E-01 Reference focal mechanism from inversion of amplitudes: station azimuth [°] distance [km] SMO BUK KAT SPA D 1-3Hz

V03, Ml=3.4, h=10.2km station azimuth [°] distance [km] JAB LAN PVE SPA A+B+CA+B+C A+B+C–>VR=5.31E-01 3D3D 3D–>VR=4.17E-01 Reference focal mechanism from inversion of amplitudes:

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