1999年5月17日万宁近海M_S4.8级地震

The Ms4.8 earthquake on May 17, 1999 in Wanning coastwise

对１９９９年５月１７日万宁近海ＭＳ４．８级地震进行了总结。分析认为，这次地震属孤立型，发震断层为ＮＥ向的兴隆－龙滚断裂和琼东南海断裂之间的次一级断裂，具有走滑特征。地震前存在３个月无ＭＬ≥３．０级地震的异常平静、低ｂ值、应变释放加速、缺震、地震频度ＧＬ高值以及琼中地磁台Ｚ分量“双低点”等前兆异常现象。地震前有不同程度的中期和短期预报。

Analyzing the Ms4.8 earthquake on May 17 1 1999 in Wanning coastwise, it is suggested that this event characterized by isolated type, and the seismogenic fault is the subsidiary fracture in the NE strike between the Xinglong -Longgun fault and the Qiongdongnanhai fault, which make a feature of strike -slip. It is considered that there are some precursor anomalies before the earthquake, such as anomalous quiescence of lacking ML≥ 3 .0 earthquake for over 3 months, low b -value, accelerating release of strain energy, high values of event lacking, earthquake frequency and GL value, and the phenomenon of 'double low points' of geomagnetic vertical component in Qiongzhong observatory, and so on. The medium - and short - term prediction in different levels before the earthquake were made.