Study on a prediction equation model for H/V response spectral ratio for shallow crustal and upper mantle in Japan
The current seismic design code in our country sets the vertical peak ground acceleration at 0.65 of the horizontal peak ground acceleration.This approach sometimes underestimates the effect of vertical ground motion and,at other times,introduces redundancy.In this study,we utilized 5258 records of earthquakes from the Japanese subduction zone with shallow crust and upper mantle.Considering the influence of spectral period and site conditions,we developed a model for the ratio of horizontal to vertical acceleration response spectra.This model is intended for practical engineering design without seismic source and path information.The research reveals:1)The earthquake type and site category significantly affect the acceleration response spectrum ratio.Therefore,when establishing the ratio model,the impact of earthquake type and site category needs to be considered.2)The coefficients for site effects in our model exhibit peaks near the average site period for each site category,consistent with the site amplification theory of one-dimensional site models.3)While our model shows a similar overall trend to Bommer(2011)model,the RHV(ratio of horizontal to vertical)in Bommer(2011)model varies little between rock,stiff,and soft sites.This difference mainly stems from the different site classification methods;Bommer(2011)is based on VS30 for site classification,representing only the stiffness of shallow surface soil layers and difficult to comprehensively reflect site characteristics.4)The proposed RHV model for practical engineering design is not specific to a particular earthquake and does not include seismic source and path parameters.However,the distribution of model residuals with respect to magnitude,fault distance,and fault depth suggests that incorporating parameters such as magnitude,source depth,and fault distance can further optimize the RHV model when explicit earthquake information is available.
RHV modelssite effecthorizontal and vertical response spectrum ratiosubduction zoneshallow crust and upper mantle earthquakessite periods
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