Characteristics Analysis Of Vertical Ground Motion

Intense vertical ground motion were recorded in several earthquakes at the end of 20th century which called many researchers' attention to the properties of vertical ground motions in the world. In this paper, based on the records from 18 earthquakes, the characteristics of vertical ground motions and vertical response spectra are analyzed. The studies of this paper are as following. 1. The existing study fruits on vertical ground motions are deep analyzed and summarized. In this paper, 659 groups of acceleration records with Mw≥4(1/2)and PGA≥20gal have been collected from 18 earthquakes, which provided enough databases. 2. The contrast studies of site classification of strong motion networks among China (include Taiwan), Japan and America proceeded in this paper. Through the comparison of different site classification standards, based on Nakanura's technique, A method is presented and utilized in transformation between different site classification standards. By this method, the predominant frequency ranges of 4 sites are determined according to China Code. 3. The statistical analysis of vertical to horizontal ratio (H/V) of PGA and response spectra. Considering to the influence of epicenter distance and site conditions on the result of collection statistics of the (H/V) PGA ratio, the rules of the statistical result of H/V PGA ration varied with different site conditions and epicenter distances are summarized. Furthermore, the rules of (H/V) spectral ratio varied with different site conditions and ground motion intensities are also studied in this paper. 4. The statistical analysis of characteristics of vertical ground motion response spectra and vertical engineering-design response spectra. Based on the 436 vertical records from 18 earthquakes, the characteristics of vertical response spectra are analyzed. The statistical results show that it is not reasonable to take 2/3 of horizontal spectra as vertical response spectra. The maximum values and characteristic periods of vertical response spectra should be determined by the statistical analysis of site conditions and earthquake intensities. Finally, by the fitting of vertical response spectra of different sites and intensities, the maximum valueα, attenuation exponential γand characteristic period Tg are determined.