The importance of crustal structure in explaining the observed uncertainties in ground motion estimation |
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| Authors: | John Douglas Hideo Aochi Peter Suhadolc Giovanni Costa |
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| Institution: | (1) ARN/RIS, BRGM, 3 avenue C. Guillemin, BP 36009, 45060 Orléans Cedex 2, France;(2) Dipartimento di Scienze della Terra, University of Trieste, via E. Weiss 1, 34127 Trieste, Italy |
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| Abstract: | In this short article, the possible reduction in the standard deviation of empirical ground motion estimation equations through
the modelling of the effect of crustal structure is assessed through the use of ground-motion simulations. Simulations are
computed for different source-to-site distances, focal depths, focal mechanisms and for crustal models of the Pyrenees, the
western Alps and the upper Rhine Graben. Through the method of equivalent hypocentral distance introduced by Douglas et al.
(2004) Bull Earthquake Eng 2(1): 75–99] to model the effect of crustal structure in empirical equations, the scatter associated
with such equations derived using these simulated data could be reduced to zero if real-to-equivalent hypocentral distance
mapping functions were derived for every combination of mechanism, depth and crustal structure present in the simulated dataset.
This is, obviously, impractical. The relative importance of each parameter in affecting the decay of ground motions is assessed
here. It is found that variation in focal depth is generally more important than the effect of crustal structure when deriving
the real-to-equivalent hypocentral distance mapping functions. In addition, mechanism and magnitude do not have an important
impact on the decay rate. |
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| Keywords: | Strong ground motion Attenuation relations Ground-motion models Ground-motion estimation equations Crustal structure France Standard deviation Equivalent hypocentral distance |
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