The Activity of the Yaziba Fault on the Lower Reaches of the Jinsha River, Southwestern China: Indirect Evidence from Paleo Earthquakes and Ancient Landslides

In this paper, in order to confirm the strong activity of the Yaziba Fault and provide information needed for disaster prevention and mitigation and safety of the reservoir, we use field investigations and remote sensing interpretations to obtain the geometry of the Yaziba Fault and the distribution of the associated nearby landslides. Several new events are dated, and the paleo earthquake events in the fault area and their time intervals are analyzed along with previously dated events. Then, a typical landslide case is analyzed, and its instability is determined using the limit equilibrium method. The main results of our study are as follows: (1) the Yaziba Fault extends for 20 km; (2) 164 landslides have occurred in the fault area, the LND reached 0.1 km⁻², and the LAP reached 0.07 for the entire research area, and the LND and LAP gradually decrease with increasing distance from the Yaziba Fault; (3) 39 dating dates are obtained and 19 paleo earthquakes are concluded, from which the time interval of earthquakes shortened from 147,000 to 3800 years ago is found; and (4) the Daomakan landslide had a 0.6 g horizontal seismic acceleration, which indicates that it was an earthquake landslide. This comprehensive method combined the geometric characteristics of the fault, paleo earthquake data, the regional landslide distribution, and the geotechnical engineering analysis of typical landslides in the area to indirectly determine the fault's activity and provide a reference for the study of fault activity in mountainous areas.

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