【摘要】 1997～2003年新疆伽师-巴楚地区发生了包含27次5级以上地震的罕见强震群活动。震群活动分别经历了1997、1998和2003年3个不同强度的地震时段。在不同时段内的5级以上地震前,地震活动均出现过不同程度的增强-平静变化。为了有效界定序列丛集(增强)-平静变化的前兆意义,寻找临震预测的时间判据,本文从地震活动过程的非线性特征入手,分析研究震群序列的时间结构特征,判定发震系统的随机性大小,确定当前序列的变异程度,进而预测序列未来的发展趋势。以震群活动区附近的喀什地震台记录的序列目录为资料,以序列中MS≥5地震为起点,以下一个5级以上地震为终点,分段统计分析地震序列的时间结构关系。主要结果为:①序列绝大部分5级以上地震前,时间变异系数均有不同程度的异常显示。②在定义δ≈1之后的10天之内,震群中发生5级以上地震的可能性很大。③时间变异系数有3种类型,即持续变异、单点变异、无变异。④5级与6级地震前的δ值变化过程相似,其值域大小没有明显区别。在震群型序列中,依据δ≈1无法准确界定当前序列的属性(前震序列还是余震序列)和判定后续震级,只能判断序列中可能会发生5级以上地震。⑤序列临界丛集性质是分层次的。只有在某一震级时,序列才会出现临界丛集变异状态。⑥时间变异系数有明确的物理意义。当地震活动出现丛集-平静现象之后,它可以清晰地描述发震系统的随机状态,进而有效界定这种丛集-平静变化是否具有前兆意义。在地震频次衰减基本正常(h>1)且无突出的丛集-平静状况下,通过时间变异系数也可以发现序列的异常变化。反之,在震群活动晚期,当出现许多地震平静现象之后,即使在h<1的状态下,时间变异系数也并未出现异常显示,这表明δ值诊断法具有较好的普适性。更多还原

【Abstract】 In 1997～2003,27 earthquakes with M≥5.0 occurred in the Jiashi-Bachu area of Xinjiang.It is a rare activity of strong earthquake swarms.In 1997,1998 and 2003,three times of activities for different magnitudes,before earthquakes with M≥5.0,the seismic activity had appeared changes of concentration-calm at different degrees.In order to delimitate effectively the prognostic meaning of concentration-calm change in sequence and seek for the time criterion of impending prediction,the non-linear characteristics of seismic activity process have been used to analyze and study the time structure characteristics of earthquake swarms sequence,further to forecasting the development tendency of earthquake sequence in the future.Taking the sequence catalogue recorded by the Kashi station as data,earthquakes with M_S≥5.0 in the sequence as a beginning and the next earthquake with M_S5.0 as the end,the time structure relations of earthquake sequence by stages statistics have been analyzed.The main result is as follows:(1)Before the major earthquakes with M≥5.0 in swarms sequence,the coefficient of the time variation(δ-value)has anomaly demonstration at different degrees;(2)Within 10 days after δ≈1,earthquake with M≥5.0 in swarms is very possible to occur;(3)The coefficient of time variation has three types of change;(4)The change process is similar before earthquakes between with M5.0 and with M6.0.Its threshold value does not have the obvious difference.In the earthquake swarms sequence,it is unable to limit accurately the attribute of the current sequences(foreshock or aftershock sequence)and to delimitate the following magnitude by the δ-value.It can only judge occurrence of earthquakes with M5.0 in the sequence;(5)The cluster characteristics of the sequence critical has some levels.Only in a certain magnitude,the sequence can have the variation state of the critical cluster;(6)The coefficient of the time variation has a clear physics meaning.It may describe clearly the random state of the earthquake occurrence.And,it is efficient to limit whether the change of the concentration-calm is the prognostic meaning or not.Under the condition of the basic normal(h>1)in sequence attenuation and having not the prominent concentration-calm,the coefficient of the time variation may also be discovered to have the abnormal change of the sequence.On the contrary,in the later period of swarms activity,after appearing much phenomena of earthquake calm in the sequence,even if in the h<1 state,the coefficient of the time variation has not appeared abnormal.更多还原