Fault Displacement Hazard Analysis for the Seismic Design of Oil and Gas Pipeline

Abstract

For the seismic design of an oil and gas pipeline crossing fault, the fault displacement is usually estimated with the empirical relationship between Magnitude and Fault displacement. It should be noted that this fault displacement may under-estimate the fault displacement imposed on the buried pipeline. Based on those strong ground motion records near the causative faults, the maximum displacement of fault movement (MFD) is larger than permanent fault displacement (PFD). With the baseline correction, fault displacement time histories were obtained from those recordings near fault during the Chi-Chi earthquake and the Wenchuan earthquake, and the relationship between MFD and PFD is developed. As an example, the response of an oil pipeline crossing the Xiaojiang fault was analyzed. The axial strain of static analysis under PFD is less than the maximum strain, but a little larger than the last residual strain in the pipeline of dynamic analysis considering the process of fault movement. It should be noticed that the recordings near fault are not enough to obtain a good model for the process of fault movement. At present, the static analysis can satisfy the need of seismic design for a pipeline crossing the fault. To consider the uncertainty, the design-basis fault displacements corresponding to the different important pipelines are suggested in this article. A new empirical relationship between the maximum fault displacement and the surface-wave magnitude is obtained with the supplemented earthquake data in East Asia.