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| Titel |
Distance and azimuthal dependence of ground-motion variability |
| VerfasserIn |
Jagdish Chandra Vyas, Paul Martin Mai, Martin Galis |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250129114
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| Publikation (Nr.) |
 EGU/EGU2016-9185.pdf |
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| Zusammenfassung |
| We investigate the near-field ground-motion variability by computing the seismic wavefield
for five previously published kinematic rupture models of the M 7.3 1992 Landers
earthquake, several simplified rupture models based on the Landers event, and a large M 7.8
scenario earthquake in Southern California. The ground motion simulations are
accomplished by solving the elasto-dynamic equations of motion using a generalized
finite-difference method. The simulated waveforms are calibrated against near-field
strong-motion recordings for the Landers earthquake. We then analyze our simulation-based
data-set of ground-motions, binned with respect to distance and azimuth to compute
mean and standard deviation of peak ground velocity (PGV). We consider different
1D-velocity-density profiles for the Landers simulations, and a 3D heterogeneous Earth
structure for the ShakeOut scenario, and for both cases we honor geometrical fault
complexity.
The ground-motion variability, σln(PGV ), estimated from numerical simulations is higher
in the near-field (Joyner-Boore distance RJB <20 km) compared to that associated with
standard ground-motion prediction equations. We find that σln(PGV )decreases with
increasing distance from the fault as a power law. The physical explanation of a large
near-field σln(PGV )is the presence of strong directivity and rupture complexity. We also show
that intra-event ground-motion variability is high in the rupture-propagation direction (both
forward and backward directivity regions), but low in the direction perpendicular to rupture
propagation for unilateral ruptures. We observe that the power-law decay of σln(PGV ) is
primarily controlled by slip heterogeneity. In addition, σln(PGV ) as function of azimuth is
sensitive to variations in both rupture speed and slip heterogeneity. We also find that the
azimuthal dependence of mean, μln(PGV ), can be approximated by a Cauchy-Lorentz
function, which may potentially help in estimation of ground motion for directive ruptures. |
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