Separation of source and site effects by generalized inversion technique using the aftershock recordings of the 2009 L’Aquila earthquake

Spectral models for ground motion prediction in the L'Aquila region (central Italy): evidence for stress-drop dependence on magnitude and depth

“…While BIN09 provided rapid insights into the spectral composition of ground motions in the aftermath of the main shock, the data set was however very limited as it was only composed of the waveforms of the main shock and 12 aftershocks with M w ≥ 4 at epicentral distances smaller than 200 km. Ameri et al (2011), hereinafter AME11, provided an entire set of spectral terms to predict ground motions after applying the GIT technique to a data set significantly larger than BIN09, containing the records of 100 aftershocks in the local magnitude range 3.1 < M l < 5.3 and hypocentral distance range 8-50 km. Malagnini et al (2011), hereinafter MAL11, studied the attenuation of a wide area of the central Apennines using a data set of 170 foreshocks and aftershocks of the L'Aquila sequence (M w ≥ 2.8) at distances up to 200 km.…”

Seismic site characterization of the Kastelli (Kissamos) Basin in northwest Crete (Greece): assessments using ambient noise recordings

“…Comparisons between HVSR applied to earthquake and ambient noise and other site effect techniques (e.g SSR, 1D TF and GIT) have shown agreement in the fundamental frequency while fluctuations in the amplification is evident suggesting a lower amplitude of HVSR (e.g Pilz et al 2009;Ameri et al 2011), compatible (e.g Horike et al 2001Rodriguez and Midorikawa 2002;Mucciarelli et al 2003b;Di Giacomo et al 2005) and at few cases higher (Nguyen et al 2004;Teves-Costa et at.1996). A generalized outcome in terms of ground amplitude is that HVSR technique can be considered as a lower bound estimator of the amplification .…”

“…Comparisons between the HVSR and other experimental and numerical studies have suggested that the HVSR amplitude can be modified due to the amplification in the vertical component of seismic motion attributed to several factors (e.g Parolai and Rischwalshi 2004;Ameri et al 2011;Bindi et al 2011;Strollo et al 2011). In cases involving sites near to source the low amplitude could be due to source to site geometry implying near vertical ray paths which induces large P wave amplitude .…”

“…Lewis et al (2007) observed that head and direct P waves are induced by the near vertical ray paths of San Andrea fault zone (California). Moreover, Ameri et al (2011) suggested for the case study of L'Acquila earthquake that the sources-to-sites geometry is capable to imply a number of near vertical ray paths due to the location of most of stations just above the hypocenters. The research outcome extracted from the above studies indicate that the observed low amplification in the spectral ratios can be associated with the amplification of the vertical component of motion which can be induced by the velocity inversion, S-P conversions or by 2D/3D effects (heterogeneities/irregularities due to Basin effects or to fault zones).…”

Density distribution functions of faults and scaling relations

“…However, if we consider a difference up to 40%, which is still reasonable taking into account all the uncertainties, the total number of datasets satisfying formula [4] becomes 16 (62%). For the datasets showing greater differences, two of them are relative to nanoseismicity from mining test sites (Kwiatek et al 2011, Gibowicz et al 1991, where the maximum value of M 0 is 3.0·10 6 and 6.8·10 7 Nm, respectively, correponding to a moment magnitude smaller than 0, which is likely too small for assuming that the earthquakes of these datasets are in the linear range of the Gutenberg-Richter law of small or moderate magnitude of tectonic earthquakes. One dataset is from fluid injection induced seismicity (Jost et al 1998) characterized by a particularly steep slope (b r ) and this could explain the misfit with formula [4], while all the others generally include local micro-or minor seismicity (Tusa et We may then conclude that, accepting a 40% difference between the slope of the ddf of r o obtained directly from the dataset and that estimated from equation [4], all the datasets relative to purely tectonic earthquakes, in the intemediate range of magnitudes, give values of the slope of the ddf of r o in agreement with equation [4].…”