Separation of source and site effects by generalized inversion technique using the aftershock recordings of the 2009 L’Aquila earthquake
Source: Bulletin of Earthquake Engineering, Volume 9, Number 3, June 2011 , pp. 717-739(23)
Abstract:We exploit S-wave spectral amplitudes from 112 aftershocks (3.0 ≤ ML ≤ 5.3) of the L’Aquila 2009 seismic sequence recorded at 23 temporary stations in the epicentral area to estimate the source parameters of these events, the seismic attenuation characteristics and the site amplification effects at the recording sites. The spectral attenuation curves exhibit a very fast decay in the first few kilometers that could be attributed to the large attenuation of waves traveling trough the highly heterogeneous and fractured crust in the fault zone of the L’Aquila mainshock. The S-waves total attenuation in the first 30 km can be parameterized by a quality factor QS(f) = 23f 0.58 obtained by fixing the geometrical spreading to 1/R. The source spectra can be satisfactorily modeled using the omega-square model that provides stress drops between 0.3 and 60 MPa with a mean value of 3.3±2.8 MPa. The site responses show a large variability over the study area and significant amplification peaks are visible in the frequency range from 1 to more than 10 Hz. Finally, the vertical component of the motion is amplified at a number of sites where, as a consequence, the horizontal-to-vertical spectral ratios (HVSR) method fails in detecting the amplitude levels and in few cases the resonance frequencies.
Document Type: Research Article
Affiliations: 1: Istituto Nazionale di Geofisica e Vulcanologia, via Bassini 15, 20133, Milano, Italy, Email: email@example.com 2: European Center for Geodynamics and Seismology, rue Josy Welter 19, 7256, Walferdange, Luxembourg 3: Section 2.1, Telegrafenberg, Deutsches GeoForschungsZentrum GFZ, Helmholtzstraße 7, 14467, Potsdam, Germany 4: Centre for Disaster Management and Risk Reduction Technology (CEDIM), Deutsches GeoForschungsZentrum GFZ, Helmholtzstraße 7, 14467, Potsdam, Germany 5: Istituto Nazionale di Geofisica e Vulcanologia, via Bassini 15, 20133, Milano, Italy 6: Università della Basilicata, via dell’Ateneo Lucano 10, 85100, Potenza, Italy 7: Istituto Nazionale di Geofisica e Vulcanologia, via di Vigna Murata 605, 00143, Roma, Italy
Publication date: June 1, 2011