Research On The Relationship Based On GIS Between The Distribution Of The Active Faults And The Seismicity In Chuandian

The chuandian region is situated in the southeastern margin of theTibetan Plateau. Since Cenozoic time, the jointed affection of eastwardmotion of the Tibetan plateau and indentation of the Assam wedge causecomplex and intense tectonic deformation and earthquakes in thisregion .It has become one of the areas with active seismicity in the chinamainland. In recent years, major and large earthquakes here occurredfrequently in the region . It has been an area of intense focus ofgeological investigations for a long time.Earthquakes are closely related with tectonic motions, especiallyactive faults. The relationship between earthquakes and active faults isone of the most important subjects in the research of seismotectonics.Most previous studies on this issue are confined to gualitative analysis .one of the reasons is the lack of effective calculation tools. In recentyears, GIS (Geographical Information System or Geo—Information System )has developed very fast both in theory and application. It has become aresearch field of cross—discipline and multi—direction. The GIStechnology has been applied to seismology . With its strong function ofspatial analysis ,it provides a new approach for the quantitative of halfquantitative study of the relationship between earthquakes and activefault population.This work uses the software ArcGIS as the basic platform to constructthe spatial database for the Chuandian region. This database includesvarious data of information such as topography, geography, earthquakecatalogues, active faults, and GPS measurements. In the view of the logicstorage structures, it contains the graph bin and attribution bin. Thegraph bin has a unified geographical coordinate system and completetopological structure. In this study, the statistical module of geologyin ArcGIS is used to make interpolation analysis of earthquakedistribution in both time and space. Then it is stacked by the spatialdistribution of active faults. With the help of other data, therelationship between earthquakes and fault distribution is displayed.This work contains the review of previous studies as well as thedevelopment of GIS application to earthquake research. The spatialanalysis capability of GIS has pronounced advantages in description oftopographical relationships between points,lines,and planes.Using GIS tostudy the mutual relation between earthquakes and distribution of activefaults will promote earthquake research.The primary work and conclusions of this are summarizes below:(1) This work has collected multi-grade earthquake catalogues,basicspatial information of geography, and date of fault distribution in thechuandian region. And attribution bins of various spatial data areestablished to provide data sources for further earthquake research. Bymaking full use of the prominent advantage of the third generation spacedata model Geodatabase of ArcGIS in space data management, this workrealizes administration to collected data attributions of earthquakes andfaults. It gives a basis for the future data search and database transfer.(2) In terms of the buffer method ,this work has made buffer analysisto the Honghe,xiaojiang,xianshuihe,and lungmenshan fault on scales of 10km,20km,and 30km,respectively. A concept of areal earthquake frequencyis proposed, which means the number of earthquakes in a unitarea.Earthquake statistics are performed to buffer areas as well as unit areasin each buffer area. The result shows that in the buffer area of 10km theearthquake density of the unit area is the largest. With increasing bufferareas, the number of earthquakes in a uint area tends to decline,thoughthe total number of events grows on magnitude order. It indicates thatthe effect of an active fault on earthquakes is confined to the range10—15km on its both sides.(3) In regard to the choice of the buffer method, this work pays moreattention to the statistics of the intersection areas of many faults. Theresult demonstrates that the earthquake frequency of a unit area in anintersected region is large by one magnitude order than that of a bufferarea in a singe fault. It means that the geologic units with differentactive faults have more potential earthquakes.(4) Spatial data analysis of DEM can help study active faults. Analysesto slopes and angles of DEM show that the both flanks of a pull-apart basinhave steep topography. If there are vertical faults, the edges of the basinwill be notably fractured.(5) ArcGIS is a GIS system with perfect functions. It has good modulesof spatial analysis and data management .All the functions of GIS can berealized by ArcGIS. In this work ,a new insight on the feature of spatialdata of earthquake catalogues has been obtained.This thesis has some problems and defects. For example, it is lackof enough knowledge on the geological setting of the chuandian region.Although there are a great number of available data, the author has notmade more efforts to collect and study these data due to the limitedworking time. Another problem is that this work is focused on geologicalstatistics and geomargrahic description, with less mechanical analysis .These problem and problems and defects will be solved in the future work.