平凉C11井水位异常变化的地震前兆信息分析

着重分析1998年以来平凉C11井水位在西海固一平凉地区5次Ms〉4．0地震前的异常特征。通过分析得到的认识是，该井水位在Ms4．0以上地震前大都存在0．5a以上的趋势异常和年变规律的变化，震前1～2个月出现较丰富的短临前兆信息，如水位固体潮畸变、日潮差波幅增大、阶跃等微动态异常，这些分析结果曾在地震预报实践中发挥较好的作用。

Analysis on the ptecursory anomaly variation of well water level at C11, Pingliang before earthquakes

The anomaly characteristics of well water level at C11, Pingliang before five Ms>4.0 earthquakes in Xihaigu-Pingliang are summarized and analyzed. The results show that there are more than half a year trend anomaly and variation of annual regular before MS >5.0 earthquake in most cases and short-imminent term precursors appear one month or two months before the earthquake, such as variation of water level solid tide, range increase of wave amplitude of date tide and leapfrog etc. The analysis has played an important role in earthquake prediction practice of Gansu Province.