Research On Dynamical Characteristics Of Historical Seismic Landslide In The Middle Of Zemuhe Fault Zone

It has proved that the seismic activity distribution of Zemuhe fault is extremelyspecial. Since the human history, strong earthquakes were mainly distributed in thenorth and south section of Zemuhe fault, while not occur in the middle of fault.According to field geological investigation, several huge landslides distributes in themiddle of fault, which have the dynamical characteristics of high speed remote debrisflow. Therefore these landslides should have been triggered by strong historicalearthquakes. This indicates whether strong earthquakes occurred in the middle ofZemuhe fault. This gives us a question that either relatively calm middle part of thefault is in tectonic stabilization or in the process of stress accumulation of potentialearthquake focus.Based on the modern landslide characteristics, we adopted the UDEC programwhich is suited to deal with discontinuous media to simulate the dynamic response ofdiscontinuous media under seismic load, and analysis dynamical characteristics ondynamic strength and high speed remote debris flow of historical seismic landslideevents. The results show that the potential slide parts of qiaowo and digu seismiclandslide are in stabilization under natural condition. Part of them collapsed while thewhole model is in limit equilibrium state under the condition of seismicaccelerated velocity (a=0.4g or a=0.6g). The entire potential slide parts collapsed withhigh speed remote debris flow under the1.2g or1.6g condition. The reason why theycollapsed is that sliding surface occurred and developed along the part where seismicaccelerated velocity is quite different. There is first terrace or second terrace in thefront of the landslide, therefore, the landslides happened before first terrace formed orafter the second terrace formed, when is between one thousand and three thousandyears, and the corresponding seismic intensity is not lower than Ⅹ or Ⅺ degree. Asthe result, it demonstrates that the middle of Zemuhe fault, which is relatively calm, isnot in tectonic stabilization, but the place of high risk of potential earthquake.