Ground motion recordings from the MW 6.3 2009 L’Aquila earthquake in Italy and their engineering implications

Abstract

The 2009 L’Aquila earthquake sequence includes the April 6 Mw 6.3 main shock and triggered events on April 7 and 9, each recorded on a digital network having five stations on the hanging wall of the main shock fault. We describe a geometric source model drawing upon inversions by others. We describe record-specific ground motion data processing that includes the incorporation of static displacements of up to 13 cm (downdrop of hanging wall). The resulting database includes 47, 38, and 31 corrected triaxial recordings from the April 6, 7, and 9 events, respectively. We present site conditions for recording stations, including recent surface wave and borehole geophysics. We demonstrate that the high-frequency data are weaker than expected for normal fault earthquakes of these magnitudes and that the data attenuate with distance at rates generally consistent with modified next generation attenuation (NGA) equations for Italy that were available prior to the event.