粤闽交界及其近海地区地震活动分析

结合东南沿海地区的地质构造背景、地震活动特点,研究粤闽交界及其近海地区(N 22.80°~24.00°、E116.50°~118.00°)地震活动特征,结果表明此区域:1具备中强地震活动的构造背景;2现代小地震呈北东方向密集成带分布在南澎列岛附近,与北东向滨海断裂的方向一致;3 6级以上地震序列类型多属主余型;4 1971年有小震记录以来,一直存在背景性的ML2级左右地震活动;ML4级以上地震活动成丛分布特征明显;中等地震(ML4~5级)的发生与本区小震活动增强之间无明显关联;当出现年平均b值低于平均值、且较上一年b值下降幅度≥0.5时,可能预示本区进入ML4级地震活跃时段,东南沿海地震带在未来1~2年内可能有中强或以上地震发生;ML4.5级以上地震前,应变能释放曲线存在加速变化。

Seismic Activity Analysis of the Junction Area of Guangdong and Fujian and Its Offshore Areas

Based on the tectonic background and seismic activity feature in the southeast coastal areas,the paper studies the characteristics of seismic activity in the junction area of Guangdong and Fujian and its offshore areas（ N 22.80° -24.00°,E 116.50° -118.00°）. The results show that： this area has tectonic setting for moderate and strong earthquake activity; modern small earthquakes were concentrated into the band with north east direction and located in the vicinity of Nanpeng island; the sequence type of earthquakes with M≥6 which can be determined belong to mainshock-aftershock type with foreshock. When small earthquake ever recorded,there has been seismic activity with ML2 earthquakes. The seismic activities of earthquakes with M ≥4 have since 1971 the characteristic of clumps distribution. There is no significant association between the increment of small seismicity in the area and the occurrence of moderate earthquakes. When the annual average b value is lower than the average value with the decrease amplitude ≥0.5 compareing to the previous year,this may indicate that this area is in a active period of earthquakes with ML≥4,and there may be moderate-strongearthquake occurring in the southeast coastal seismic belt in the next 1-2 years. Before the ML4.5 earthquakes,there is acceleration variations in release curve of strain energy exist.