云南年度危险区预测能力的统计分析

通过对云南省地震局1989—2006年度地震趋势研究报告中年度预测水平、 危险区圈定和实际发生地震情况等统计分析, 结果显示云南地区每年发生2.8组M≥5地震, 3年发生2组M≥6地震, 发震的自然概率较高, 1989年以来年度地震活动水平预测为M≥6的对应率较高, 达到了56%。 危险区的预测不能用异常数量的多少来判定, 对于M≥6地震, 应用4级地震频度增长显著的区域和高水位异常区域等指标能更好的预测危险区。 5级地震在云南地区有的时候异常出现最多就是2～3个月就发震, 年度很难用异常判断级地震的危险区, 但5级地震也存在10年左右的主体活动地区迁移现象, 利用主体活动地区的特征可以提高5级地震发生区域的预测能力。 年度应重点跟踪M≥6地震, 由于云南地区6级以上地震发生前中小地震活动增长和前兆异常出现后, 对应地震的时间从几个月到3年不等, 但半年尺度前兆异常数量增加显著, 因此在看到地震活动增强后动态跟踪前兆的变化, 采用长、 中、 短、 临渐进式的预报方式, 仍然是目前提高地震预报效能最有效的途径。

Statistical Analysis on Forecasting Ability of Annual Key Regions with a Certain Seismic Risk in Yunnan Region

The annual forecasting level, determination of earthquake risk areas and the actually occurred earthquakes in Yunnan region, which were recorded in the research report of annual earthquake tendency consultation between 1989—2006 have been analyzed in this paper. The results show that the annual occurrence rate for the earthquakes with M≥5.0 is about 2.8 groups and the triennially occurrence rate for earthquakes with M≥6.0 is about 2 groups in Yunnan region. As a result of the high natural probability of strong and moderately-strong earthquakes, the forecasting level of M≥6.0 earthquakes reached 56% since 1989. The level of risk areas forecast can not be determined by the number of risk areas. The application of some indices can help us improve the risk areas forecasting level for the earthquakes with M≥6.0, such as the areas with the frequency of M4.0 earthquakes show obvious intensifying phenomena and the areas with high water level anomaly. The longest time interval between the M5.0 earthquakes happened and the precursory anomalies appeared is 2～3 months in Yunnan region, so it is hard to determine the risk areas for M5.0 earthquakes based on the research report of annual earthquake tendency consultation, but the main seismic areas for M5.0 earthquakes exist migration pattern, using this feature can improve the risk areas forecasting level for M5.0 earthquakes. The research report of annual earthquake tendency consultation should focus on the earthquakes with M≥6.0, before M6.0 earthquakes, the time interval between moderately-small earthquake activities intensified, precursory anomalies appeared and corresponding earthquakes happened ranged from several months to 3 years,but precursory anomalies show obvious intensification in 6 months before the earthquakes with M≥6.0 happened in Yunnan region. If the earthquake activities intensified, we should dynamically trace the change of the precursory anomalies. The long-medium-short-impending progressive forecasting method is the most effective way to improve the earthquake forecasting level at present.