2012 Volume 29 Issue 2 Pages 23s-39s
Given the different geology and earthquake activity, establishing a regional attenuation relationship is deemed important for the seismic design of structures. This paper presents a new equation in place of the relationship currently used in Vietnam for horizontal ground motion based on database sets compiled from strike-slip and shallow crustal earthquakes with magnitudes ranging from 3.0 ≤ Mw ≤ 6.9 and source distances of up to 300 km for northern Vietnam. This new equation estimates the ground motion in terms of moment magnitude, distance and site conditions for strike-slip earthquakes. The equation is derived based on a regression analysis of earthquake records; in this study, the database consists of earthquake records from Japan, Vietnam and adjacent areas. We also assume a few simple relationships, such as the relationship between Mw and Ms, the closest distance to the fault and the effects of shallow site conditions on the average shear-wave velocity in the upper 30 m to develop a comparison with existing relationships. The new equation for northern Vietnam corresponds better with other equations for near- and far-field distances than the equations currently used for seismic design in Vietnam.