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Variability of Near-Field Ground Motion from Dynamic Earthquake Rupture Simulations

Summary: Variability of Near-Field Ground Motion from Dynamic
Earthquake Rupture Simulations
J. Ripperger, P.M. Mai, J.-P. Ampuero
Institute of Geophysics, ETH Zurich, 8093 Zurich, Switzerland
Abstract. This study investigates near-field ground motion variability due to dynamic
rupture models with heterogeneity in the initial shear stress. Ground velocity seismo-
grams are synthesized by convolving the time histories of slip velocity obtained from spon-
taneous dynamic rupture models with Green's functions of the medium calculated with
a discrete wavenumber / finite element method. Peak ground velocity (PGV) estimated
on the synthetics generally matches well with an empirically derived attenuation rela-
tion, whereas spectral acceleration (SA) only shows an acceptable match at periods longer
than 1 s. Using the geometric mean to average the two orthogonal components leads to
a systematic bias for the synthetics, in particular at the stations closest to the fault. This
bias is avoided by using measures of ground motion that are independent of the sensor
The contribution from stress heterogeneity to the overall ground motion variability is
found to be strongest close to the fault and in the backward directivity region of uni-
laterally propagating ruptures. In general, the intra-event variability originating from the
radiation pattern and the effect of directivity is on the same order or larger than the
inter-event variability. The inter-event ground-motion variability itself is dominated by


Source: Ampuero, Jean Paul - Division of Geological and Planetary Sciences, California Institute of Technology


Collections: Geosciences