Propagation of surface waves from the Greek earthquakes across Europe R. Gazdova 1,2, P. Kolinsky 1, J. Malek 1 & PASSEQ working group 1 Academy of Sciences of the Czech Republic - Institute of Rock Structure and Mechanics 2 Charles University in Prague – Faculty of Science ESC 2010, Montpellier, France, September 8, 2010

map of used seismic stations and EQs data: ORFEUS PASSEQ Czech Regional network IRSM stations Eartquakedate centroid time latitudelongitude depth [km] MwMs :57: :17: :09: :09: :08: :27: :25:

GREECE EQ AT STATION KHC (Czech republic) epicentral distance: 1393 km , 12:25:29.89 GMT Mw = 6.4, Ms = 6.1 Rayleigh wave Love wave classical approach – one station

regional approach – many stations classicalregional approach one stationmany stations many periodsone period (consecutively many p.) one dispersion curveno dispersion curve identification of several modesidentification of one mode at one stationat many stationsadvantage easy identification of the dispersioneasy identification of the modes (fundamental, higher, reflected)

multiple filtering Gaussian filters constant relative resolution filtering instantaneous period estimation SVAL surface wave analysis spectrum frequency (Hz) time (s)

five local envelope maxima of all quasiharmonic components obtained by the inverse Fourier transform are found and their propagation times determined maxima represent different modes of direct surface waves as well as possible reflected, converted and multipathed modes

predominant directions of surface wavefront propagation of different modes are estimated by sorting the found propagation times across Europe according to their temporal and spatial correlation with implications for location of the scattering heterogeneities and reflection structures in Central Europe time (s) for 1 period: 173 stations * 5 maxima = 865 arrival times at 1 filter we use approx. 100 filters for 1 station = arrival times

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Rayleigh waves, R component, 50 s

50 s Tornquist-Teisseyre zone

preliminary results method of regional surface wave mode identification was introduced fundamental and first higher modes were identified reflections of fundamental modes were found propagating from the Aegean Sea, Rayleigh waves pronounce significant first higher mode (R and Z component) as opposed to that, Love waves do not reflection from Tornquist-Teisseyre zone were found at 50 s for Rayleigh waves (R component)