Modelling of the Normal Fault Pattern above a Basement Horst in the Lufeng Sag, China

Sammanfattning: The analogue models and the kinematic models based on the seismic data results were used to simulate the fault pattern which develops above a basement horst. The two major normal faults intersect with each other along the strike in the sedimentary covers. The fault pattern developed in the sedimentary cover is controlled by the dip of the basement fault and the width of the basement horst. The single horst structure was only developed in the sedimentary covers above the wider end of the basement horst. The hourglass structure was developed in the sedimentary covers above the narrower end of the basement horst. The precursor faults developed ahead of the major second-order normal faults when the dip angle of the basement fault is larger than 60°. The antithetic faults developed ahead of the major second-order normal faults when the dip angle of the basement fault is less than 50°. The analogue models were designed in a way that the two hanging wall blocks glide down along the basement horst simultaneously to simulate the activity of the basement faults. The kinematic models were designed based on the alternative sequential slip method to study the kinematic behaviors of the conjugate normal faults. The Lufeng Sag was characterized by the basement horst in the center and the deep half-grabens developed beside the horst. The width of the basement horst decreases along its strike. The models indicates that the second-order normal faults developed above the basement horst, observed in the Lufeng Sag seismic profiles, were reproducible and much more detailed structures were revealed