PRELIMINARY STUDY OF CHARACTERISTIC EARTHQUAKES IN THE XIANSHUIHE FAULT ZONE

The characteristic earthquake is a main manifestation of large earthquakes repeated in the same place. The present information suggests that large earthquakes on the Xianshuihe fault may follow the characteristic earthquake model,for which the uniformity of earthquake fault length,coseismic displacement and fault slip pattern all remain for a relatively long time. The cumulative dislocation distribution at a given section along the fault shows variation consistent with the displacement by a single earthquake because of reccurrence of the events at the same place,and thus causing synchronous variations of slip rates. Taking the coseismic fracture segment of the Luhuo earthquake of 1973 as an example,this paper discusses the phenomena of the characteristic earthquake at the Xianshuihe fault. The seismicity of this segment does not follow the linear frequency-magnitude relationship described by Gutenberg and Richter because it is controlled by the characteristic earthquake model. This model not only has great influence on fault produced landforms and fault slip rates,but also has great significance in the research on seismic activity since it implies that characteristic events dominate earthquake recurrence and the lack of moderate-magnitude events.