1999年9月21日台湾省集集强余震序列发生时间的规律性

The regularity of the time that the series of strong aftershocks occurred at Jiji Taiwan province of China in Sep 21 1999

使用1999年9月20日至11月1日的CDSN宽频带（BPZ）地震记录,对台湾省集集地震的强震震级、震源性质、震源物理参数和发生时间进行研究。主要结果:①确定集集地震是强震群类型的地震活动,主震[m(T)8.51,MW7.3]位于中央山脉上,横切中央山脉的北西向北斗-玉里断裂,是主要地震活动构造;②集集强震序列的平均应力降△σ为4.272×103kPa,平均视应力ησ为2.136×103kPa,它们是地震断层面上随着震源尺度等变化而变化的物理量;③决定地震效率η的震源释放能量-△E和传播地震波能量Es,分别从BPZ地震波5个倍频程的滤波数据和假设视应力等于二分之一应力降的条件下求取;④强余震的发震时间对数lg△t（时间单位为s）,与一些震源物理参数有显著的负相关性,证实了能量积累多、应力积聚高的地方率先发震。并且第一次强震以后,强余震发生时间和强度之间保持显著的衰减关系。这些关系式,如△t=1015.54-1.48m（r）和△t=1017.55-2.00MW等,对早期识别出如同集集强震群类型的地震活动时,预测强余震时间和强度有实际应用意义。

With the CDSN's broadband records (BPZ) of the strong earthquake group at Jiji, Taiwan province of China (1999-09-20～1999-11 -01), the magnitude of strong shocks, the properties and physical parameters of the focus were investigated. The results are as follow: (1) Jiji earthquake can be classified as the type of strong shock group of earthquake activity. The main shock (m(T)8.51, MW7.3) was located at the center cordillera. The major strong earthquake active construct is Beidou-Yuli fault, which cut across the center cordillera and is in northwest direction. (2) The average stress drop △σ of the series of Jiji strong shocks was 4.272×103 kPa, and the average apparent stressησ was 2.13×103 kPa. They are the physics quantities on seismic fault plane, changing with the variation of the focus physical parameters such as the size of focus. (3) The energy released in focus -△E and the energy radiated as earthquake wave energy Es, with which the earthquake efficiency η can be determined, can be gotten from the filtered BPZ records under the assumption that the apparent stress is equal of the half of the stress drop, respectively. (4) The logarithm lg△t (unit of time: second) of the occurring time of the Jiji strong aftershocks was negative correlated with some focus physical parameters and the intensity of the earthquakes, approving that the place where more energy and higher stress accumulated shocks first, and after the first strong shock, the time and intensity of strong aftershock hold an obvious attenuation relationship. The correlation functions, e.g. △t = l015.54-1.48m(r) and △T = 1017.55-2.00Mw have applied significance for forecasting the time and intensity of strong aftershocks, if the earthquake can be distinguished as the type of Jiji strong shock group early.