青藏块体东北缘中强地震前小震频度异常研究
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摘要
1980年以来青藏块体东北缘共发生26次MS5.0以上地震,其中22次在时间和空间上相对独立。通过系统研究这22次中强地震前其邻区小震活动的增强现象,发现有17次中强地震前存在比较明显的小震增强现象。虽然小震增强现象在多数中强地震前存在,但是利用小震活动的增强对未来中强地震的预测比较困难。文中结合青藏块体东北缘小震活动的特点,尝试提出根据小震活动空间格局是否改变统计小震频度的方法,并且进行了初步的应用。结果表明:利用新方法统计小震的频度更能突出中强地震前的小震频度异常,并且中强地震前的小震频度异常幅度受空间范围大小的影响不大,能够有效的提取青藏块体东北缘中强地震前的中短期异常指标。
26 MS≥5.0 earthquakes were recorded in the northeast margin of Qinghai-Tibet block since 1980,in which 22 medium-strong earthquakes are independent in space and time.Study of seismicity increasing before the 22 medium-strong earthquakes shows that small earthquakes increasing occurred before 17 medium-strong earthquakes.Though seismicity increasing is a common phenomenon in the northeast margin of Qinghai-Tibet block,we have difficulty in predicting the medium-strong earthquakes by this phenomenon alone.In order to predict the medium-strong earthquakes through seismicity increasing,this paper tries to propose a new method which calculate small earthquake frequency through the changing pattern of small earthquake activities based on the character of small earthquake activity in the northeast Qinghai-Tibet block and then make primary application,the result showed that we can get obvious anomaly frequency of small earthquake before medium strong earthquake through the new method,and it is affected very little from the range of area where small earthquakes occurred.We can get medium to short term anomaly index in the northeast margin of Qinghai-Tibet block.
26 MS≥5.0 earthquakes were recorded in the northeast margin of Qinghai-Tibet block since 1980,in which 22 medium-strong earthquakes are independent in space and time.Study of seismicity increasing before the 22 medium-strong earthquakes shows that small earthquakes increasing occurred before 17 medium-strong earthquakes.Though seismicity increasing is a common phenomenon in the northeast margin of Qinghai-Tibet block,we have difficulty in predicting the medium-strong earthquakes by this phenomenon alone.In order to predict the medium-strong earthquakes through seismicity increasing,this paper tries to propose a new method which calculate small earthquake frequency through the changing pattern of small earthquake activities based on the character of small earthquake activity in the northeast Qinghai-Tibet block and then make primary application,the result showed that we can get obvious anomaly frequency of small earthquake before medium strong earthquake through the new method,and it is affected very little from the range of area where small earthquakes occurred.We can get medium to short term anomaly index in the northeast margin of Qinghai-Tibet block.
引文
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[2]茂木清夫.地震前兆现象产生的机制[J].世界地震译丛,1994,4:11-16.
[3]刘蒲雄.强震前地震活动增强特征[J].地震,1982,2(2):5-7.
[4]刘蒲雄,陈兆恩,高伟,等.大震前地震活动图像演变及中期向短期过渡的地震活动性标志[J].地震,1997,17(2):113-125.
[5]杨立明,车时.大震前后中强地震活动格局变化及其预测意义初步研究[J].西北地震学报,2004,26(3):212-217.
[6]马宏生,刘杰,张国民,等.用应变积累释放模型研究中国大陆地块分区地震活动[J].地震学报,2002,24(6):569-578.
[7]宋治平,梅世蓉,尹祥础.强大地震前地震活动增强区及其力学研究[J].地震学报,1999,21(3):271-277.
[8]刁守中,刘西林,华爱军.苍山5.2级地震异常群体时空演化特征[J].东北地震研究,2002,18(2):1-9.
[9]黄圣睦,董瑞英.地震活动图像特征与强震危险区经验性预测依据的初步研究[J].四川地震,2005,117(4):12-20.
[10]谢智,刘尧兴,谢健健,等.河南及邻区5级以上地震前中等地震活动增强特征[J].地震,2001,21(2):70-74.
[11]任雪梅,马禾青,赵知军,等.宁夏及邻区5级以上地震前中等地震活动增强特征研究[J].西北地震学报,2002,24(3):267-272.
[12]程建武,杨立明,王振亚.祁连山地震带地震活动性增强现象研究[J].西北地震学报,2002,24(4):330-334.
[13]兰从欣,朱红彬,郭心.首都圈地区中等地震前小震活动异常特征分析[J].华北地震科学,2003,21(1):11-14.
[14]易桂喜,韩渭宾.四川及邻区强震前地震活动频度的变化特征[J].地震研究,2004,27(1):8-13.
[15]王筱荣.新疆强震前地震活动增强研究[J].华南地震,2005,25(1):17-23.
[16]吕培苓.湖北西部地区小震活动与台湾强震关系研究[J].地震,2004,24(1):71-75.
[17]陈学忠,郭祥云,李艳娥.首都圈地区小震活动月频次分布特征[J].地震,2007,27(4):36-42.
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