Test Of Seismic Zoning Map (1973) Of Xichang-Dukou Region

Seismic zoning maps provide a seismic precautionary criterion for general buildings,playing an important role in seismic precautionary work and earthquake mitigation system.However,the most deadly 12 large earthquakes in the 21 st century have occurred in places mapped as having relatively low hazard,that challenges seismic zoning maps and the methods which need rigorous and objective test.This paper discusses the method of testing seismic zoning maps and tests the “Xichang – Dukou region seismic intensity zoning map(1973)" with the actual earthquake data after the seismic zoning map published,providing a reference for further research and development of the seismic zoning map compilation method.The main contents are as follows:(1)This paper introduces the seismic risk zoning and intensity zoning map of Xichang – Dukou region.At that time the expert group summarized the seismic activity characteristics and seismogeology characteristics,and generalized geomorphological symbol of different intensity seismic risk area.This paper describes the conclusion of predicting the seismic activity of Shimian-Yuanmou seismic belt in 100 years by four methods including N-M relation curve extrapolation,linear prediction,Markov process and exceedance probability method.The seismic hazard zoning map and seismic intensity zoning map of Xichang-Dukou region were given out.(2)This paper organizes the shallow earthquake catalogue of M?5 in 1973-2014 occurring in the north-south seismic belt,Shimian-Yuanmou seismic belt and Xichang – Dukou region,that each number is 68,27 and 20(4 out of the region).This paper collects and sorts 11 intact isoseismal lines,complements and perfects 2 incomplete isoseismal,and generates the isoseismal of the other 7 esrthquakes in and near Xichang – Dukou region with seismic intensity attenuation relationship.The coordinates of epicenters and isoseismal are united with seimsmic zoning map by projection transformation,affine and vector quantization.(3)This paper tests the prediction of seismic activity at that time,comparing the actual number,time and space of strong earthquake with prediction where the frequency in 42 years is converted by 100 years.The result is acceptable,that the prediction is greater when the space range is larger,and especially the prediction is very valuable that a M?7 earthquake would occur in Songpan – Maowen.As the space is narrow,the magnitude of prediction decreases,the result is poor.(4)This paper paints the epicenter of I?? earthquakes on the seismic harzed zoning map to test if in the high risk zone.2 of 3 strong earthquakes did not occur in the judged I?? zone,which is amiss.(5)In this paper,the seismic intensity distribution is tested.Every isoseismal is overlaid on the map and the total areas with observed intensity of 1 degree,2 degrees,with a total of 3 degrees(or more)higher than the corresponding intensity on the map are sumed.The result indicates that the underestimate of seismic zoning map distributes on the low risk zone,and the serious underestimate focuses on the I=? zone.