Bounds on the distribution of amplitudes in ground motion prediction models

Jeff Fisher, Paul Somerville, John Zhao, Jian Zhang

Research output: Chapter in Book/Report/Conference proceedingOther chapter contribution


In current ground motion models, the uncertainty in predicted ground motion is modelled with a lognormal distribution. One consequence of this is that predicted ground motions do not have an upper limit. In reality, there probably exist physical conditions that limit the ground motion. Use of unbounded models in probabilistic seismic hazard analysis leads to ground motion estimates that may be unrealistically large, especially at the low annual probabilities considered for important structures, such as dams or nuclear reactors. Due to the limited size of earlier strong motion data sets, statistical analysis of the distribution of earthquake ground motion amplitudes was unable to provide a clear point at which to truncate the lognormal distribution. Recently, very large data sets of strong motion recordings have become available, making statistical analysis more viable. We have analysed very large strong motion data sets from the K-net and Kik-net strong motion networks in Japan. Preliminary analyses by us and other investigators using normal probability plots show departures from lognormal behaviour at about 2.5 standard deviations above the median. Our basic approach is to calculate residuals of the recorded data from the ground motion model developed for Japan by Zhao et al. (2006) using the K-net and Kik-net data. These residuals are then used to construct normal probability plots, and the significance of departures of the residuals from lognormal distributions is quantified. The significance of departures is assessed in light of earthquake source, wave propagation, and site response effects that may be present in the data but not taken into account in the ground motion model of Zhao et al. (2006) that form the basis for measurement of residuals.
Original languageEnglish
Title of host publicationEarthquake engineering in Australia
Subtitle of host publicationconference : 2006 : proceedings of a conference held by the Australian Earthquake Engineering Society : Canberra, ACT : 24-26 November 2006
EditorsKevin McCue, Sonja Lenz
Place of PublicationJamison, A.C.T.
PublisherAustralian Earthquake Engineering Society
Number of pages5
ISBN (Print)0646469215
Publication statusPublished - 2006
EventAustralian Earthquake Engineering Society Conference - Canberra
Duration: 24 Nov 200626 Nov 2006


ConferenceAustralian Earthquake Engineering Society Conference


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