Instrumental strong-motion recordings available for Italy only includes data from a few strong earthquakes of the last 20-30 years and cover a very limited portion of the national territory. This prevents the possibility of using them to reliably model regional variations of seismic attenuation properties at a scale shorter than several hundreds of km. On the contrary, quite reliable seismic intensity observations, relative to significant earthquakes of the last four centuries, are very abundant (about 30,000) and cover most of the inland territory. In this work we computed an improved version of the recently published tomographic inversion of seismic intensity attenuation (Carletti and Gasperini, 2004), cast on a grid with mesh resolution of 50 km, that was formerly found to be well in agreement with physical properties of the Italian crust, like the surface heat flow. For these new computations we used an extended intensity database as well as an improved tomographic inversion method. We also compared the statistical significance of different attenuation models including geometrical spreading and a bilinear anelastic dissipation term to find the most reliable description of seismic intensity attenuation behavior in Italy. Under the assumption of a linear relation between intensity and the logarithm of physical parameters like ground acceleration and velocity we also deduced a map in term of total seismic Quality factor that could be directly used to tune regional attenuation laws to be used in hazard computations.
Ground motion attenuation heterogeneities in Italy inferred from seismic intensity tomography
PASOLINI, CHIARA;GASPERINI, PAOLO;LOLLI, BARBARA
2004
Abstract
Instrumental strong-motion recordings available for Italy only includes data from a few strong earthquakes of the last 20-30 years and cover a very limited portion of the national territory. This prevents the possibility of using them to reliably model regional variations of seismic attenuation properties at a scale shorter than several hundreds of km. On the contrary, quite reliable seismic intensity observations, relative to significant earthquakes of the last four centuries, are very abundant (about 30,000) and cover most of the inland territory. In this work we computed an improved version of the recently published tomographic inversion of seismic intensity attenuation (Carletti and Gasperini, 2004), cast on a grid with mesh resolution of 50 km, that was formerly found to be well in agreement with physical properties of the Italian crust, like the surface heat flow. For these new computations we used an extended intensity database as well as an improved tomographic inversion method. We also compared the statistical significance of different attenuation models including geometrical spreading and a bilinear anelastic dissipation term to find the most reliable description of seismic intensity attenuation behavior in Italy. Under the assumption of a linear relation between intensity and the logarithm of physical parameters like ground acceleration and velocity we also deduced a map in term of total seismic Quality factor that could be directly used to tune regional attenuation laws to be used in hazard computations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
