粤闽交界及其近海地区地震活动分析
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摘要
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。
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.
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.
引文
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[2]张培震,邓起东,张国民,等.中国大陆的强震活动与活动地块[J].中国科学(D辑),2003,33(增刊):12-20.
[3]刘以宣.华南沿海区域断裂构造分析[M].北京:地震出版社,1981.
[4]姚伯初,曾维军,陈艺中,等.南海北部陆缘东部的地壳结构[J].地球物理学报,1994,37(1):27-35.
[5]Yan P,zhou D,Liu Z S.A crustal structure profile across the northern continental margin of the South China Sea[J].Tectonophysics,2001,338:1-21.
[6]赵岩,张毅祥,姜绍仁,等.南海北部地球物理特征及地壳结构[J].热带海洋学报,1996,15(2):37-44.
[7]阎贫,刘海龄.南海北部陆缘地壳结构探测结果分析[J].热带海洋学报,2002,21(2):1-12.
[8]陈定国.1918年南澳地震的震中位置[J].华南地震,1986,6(3):14-19.
[9]国家质量技术监督局,国家标准化管理委员会,GB17741-2005工程场地地震安全性评价[S].北京:中国标准出版社,2005.
[10]卢寿德.工程场地地震安全性评价(GB 17741-2005)宣贯教材[M].北京:中国标准出版社,2006.
[11]潘华,鄢家全,张志中,等.1918年南澳7.3级地震与强余震之参数复核[J].震灾防御技术,2009,4(1):40-48.
[12]郭斌,王斌,张月辉.苏北-南黄海盆地地震构造基本特征[J].华北地震科学,2013,31(1):38-44.
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