Fault growth analysis of the Gaoqing-Pingnan fault, Bohai Bay, China

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2020-09-29

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Previous studies have suggested the growth of faults during the early Cenozoic within the Bohai Bay basin, China, was due to changes in plate tectonic stresses. The goal of this project was to analyze the Gaoqing-Pingnan fault growth in the Bohai Bay Basin, China, to shed insights on this geologically complex region. The fault has an abnormal zig-zag map-view geometry that shows abrupt strike changes along the fault. We seek to understand how the changes of strike along the fault could have developed. In order to answer this question a sedimentary basin analysis was performed of the region. Eight seismic lines and biostratigraphic wellbore data from 152 wells were used to interpret numerous stratigraphic horizons across the Gaoqing-Pingnan fault of Eocene to present-day ages. The fault throw of each horizon was measured across the fault on each seismic line and plotted in relation to the distance along the fault from west to east. The plot revealed a kinked fault distance-displacement relationship that was characteristic of fault linkage. In this model, two separate faults form, grow toward each other, and eventually merge into one unified fault. Understood within the context of the fault linkage model, each region of distinct strike along the Gaoqing-Pingnan fault was originally an independent, discrete fault. The point of change in fault strike can be attributed to later fault linkage zones. This understanding of the Gaoqing-Pingnan fault growth history may help shed light on the broader geologic events that impacted the Bohai Bay Basin. This project was completed with contributions from Yin Liu from China University of Petroleum.

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