TEMPORAL AND SPATIAL VARIATION CHARACTERISTICS OF B VALUE IN SHAANXI-GANSU-NINGXIA BORDER REGION
The b-value temporal and spatial scanning method is applied to the Shaanxi-Gansu-Ningxia border area to analyze the risk of future seismic trends.By tracing the earthquake cases of ML5.0 or above in the stud-y area,the results show that that 56％of the moderate earthquakes occur in the region with low b-value and its edge.The low b-value anomaly area has certain indicative significance for the seismogenic region of moderate and strong earthquakes.Four anomaly areas with low b-values are selected from the b-value spatial distribution map for time scanning.It was found that occurrence of moderate and strong earthquakes in the Haiyuan Fault zone and its adjacent areas has a relatively good correspondence with the time of b-value decrease,and the b-value of the southern section of the Liupanshan fault zone and the northern section of the Longxian-Baoji fault zone has been declining for several years.Combining the characteristics of locked fault zones and seismic gap from other researchers'studies,it is concluded that the Haiyuan fault zone and its surrounding areas should be vigilant for the risk of moderate to strong earthquakes due to a decrease in the b-value in the future,and strong earthquakes may occur in the southern section of the Liupanshan fault zone and the northern section of the Longxian-Baoji fault zone and their surrounding areas in the future.Finally,the effects of mine earthquake,af-tershock and minimum integrity magnitude(Mc)on the results of b-value calculation are analyzed.
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