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|Authors: ||Ameri, Gabriele*|
|Title: ||Testing the improvement of ShakeMaps using f inite-f ault models and synthetic seismograms|
|Issue Date: ||6-Sep-2010|
|Abstract: ||ShakeMap package uses empirical ground motion prediction equations (GM PEs) to
estimate the ground motion where recorded data are not available. Recorded and
estimated values are then interpolated in order to produce a shaking map associated
to the considered event. Anyway GMPEs account only for average characteristics
of source and wave propagation processes. Within the framework of the
DPC-INGV S3 project (2007-09), we evaluate whether the inclusion of directivity
effects in GMPEs (companion paper Spagnuolo et al., 2010) or the use of synthetic
seismograms from finite-fault rupture models may improve the ShakeMap
evaluation. An advantage of using simulated motions from kinematic rupture models
is that source effects, as rupture directivity, are directly included in the synthetics.
This is particularly interesting in Italy where the regional GMPEs, based on a few
number of near-source records for moderate-to-large earthquakes, are not reliable for
estimating ground motion in the vicinity of the source.
In this work we investigated how and if the synthetic seismograms generated with
finite-fault models can be used in place of (or in addition to) GMPEs within the
ShakeMap methodology. We assumed a description of the rupture model with
gradually increasing details, from a simple point source to a kinematic rupture
history obtained from inversion of strong-motion data. According to the available
information synthetic seismograms are calculated with methods that account for the
different degree of approximation in source properties.
We chose the M w 6.9 2008 Iwate-M iyagi (Japan) earthquake as a case study. This
earthquake has been recorded by a very large number of stations and the
corresponding ShakeMap relies almost totally on the recorded ground motions.
Starting from this ideal case, we removed a number of stations in order to evaluate
the deviations from the reference map and the sensitivity of the map to the number
of stations used.
The removed data are then substituted with synthetic values calculated assuming
different source approximations, and the resulting maps are compared to the original
ones (containing observed data only). The use of synthetic seismograms computed
for finite-fault rupture models produces, in general, an improvement of the
calculated ShakeMaps, especially when synthetics are used to integrate real data.
When real data are not available and ShakeMap is estimated using GMPEs only, the
improvement adding simulated values depends on the considered strong-motion
|Appears in Collections:||Conference materials|
04.06.99. General or miscellaneous
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