research
Task 3 - Molise - Deliverable D7: Validation shaking scenarios.
- Publication date
- Publisher
Abstract
The main goal of this report is the computation of the bedrock seismic motion at 5
municipalities located in the Molise area (Bonefro, S.Giuliano, Colletorto, S.Croce di
Magliano, Ripabottoni, hereafter referred to as sites BNF, SGI, CLT, SCM and RPB,
respectively). This area represents one of the validation case studies, planned in the
framework of Project S3 which aim is the production of ground shaking scenarios for
moderate magnitude earthquakes. Indeed, the recently occurred Molise earthquake
represents a proper opportunity to compare synthetic simulations with real data.
Acceleration time series were recorded during the October 31, 2002 and November 1,
2002 main shocks by analog and digital instruments managed by the Italian Civil
Protection Department [DPC-SSN, 2004] while acceleration and velocity records
were collected during the first month of seismic activity by DPC, INGV, INOGS,
Dip.Te.Ris.(Genoa) (see §2.1 and Deliverable D6). Both strong and weak motion data
were employed to infer regional ground motion prediction equations and spectral
attenuation models (§2.3 and §2.4) while acceleration time series recorded during the
first main shock by nearby stations were used to constrain the seismogenic sources
of the October 31 and November 1, 2002 twin earthquakes (§4.1).
Bedrock shaking scenarios at different level of complexity were produced by ground
motion prediction equations (scenarios of level 0, §4.2), high frequency (f>1Hz)
simulations (scenarios of level I, §4.3) and broad band (0-12 Hz) simulations
(scenarios of level II, §4.4). Comparison of results obtained with different simulations
methods confirms the complexity of the Molise area as regard to both seismogenic
and attenuation properties of the crust. Especially for this area the ground motion
prediction is constrained by the demand of simulations reproducing different
features of the seismic wavefield. In particular, the input motion for site effect
modelling, performed at sites located in the epicentral area, was computed with a
broad band technique able to reproduce the complete wave field in the frequency
band 0-10 Hz in terms of acceleration time series (scenarios of level II scenarios)