The Characteristics of the Precursory Anomaly prior to the Yiliang Earthquakes,Yunnan,China on September 7,2012

An analysis was carried out on the seismic activity and the precursory anomaly prior to the earthquakes in Yiliang on September 7,2012. The characteristics of the seismic activity,the dynamic changes of underground fluid and deformation were investigated. As a result of the investigation,we found that: before the earthquake,the seismicity level of M4. 0earthquakes had enhanced,and seismic gap of a small earthquake had appeared; the precursory anomalies emerged about 1 year before the earthquake; there was phenomenon of short-term anomaly migrating from the periphery to the epicenter area; the imminent anomaly appeared in a relatively concentrated period of time, a week before the earthquake. The research has shown a significant guidance for the analysis and prediction of strong earthquakes( Ml> 5. 0).

Application of logistic regression model for hazard assessment of landslides caused by the 2012 Yiliang Ms 5.7 earthquake in Yunnan Province,China

Accurate assessment of seismic landslides hazard is a prerequisite and foundation for postdisaster relief of earthquakes.An Ms 5.7 earthquake occurring on September 7,2012,in Yiliang County,Yunnan Province,China,triggered hundreds of landslides.To explore the characteristics of coseismic landslides caused by this moderate-strong earthquake and their significance in predicting seismic landslides regionally,this study uses an artificial visual interpretation method based on a planet image with 5-m resolution to obtain the information of the coseismic landslides and establishes a coseismic landslide database containing data on 232 landslides.Nine influencing factors of landslides were selected for this study:elevation,relative elevation,slope angle,aspect,slope position,distance to river system,distance to faults,strata,and peak ground acceleration.The real probability of coseismic landslide occurrence is calculated by combining the Bayesian probability and logistic regression model.Based on the coseismic landslides,the probabilities of landslide occurrence under different peak ground acceleration are predicted using a logistic regression model.Finally,the model established in this paper is used to calculate the landslide probability of the Ludian Ms 6.5 earthquake that occurred in August 2014,78.9 km away from the macro-epicenter of the Yiliang earthquake.The probability is verified by the real coseismic landslides of this earthquake,which confirms the reliability of the method presented in this paper.This study proves that the model established according to the seismic landslides triggered by one earthquake has a good effect on the seismic landslides hazard assessment of similar magnitude,and can provide a reference for seismic landslides prediction of moderate-strong earthquakes in this region.