东南沿海地震带20世纪第Ⅳ活跃幕的两个特征

Two Characteristics of the Ⅳ Active Episodes in Seismic Belt of Southeast China Coast in 20th century

研究了东南沿海地震带20世纪第Ⅳ活跃幕的两个特征,包括该带中强地震与阳江地震窗的对应关系以及该带ML4地震长时间平静的震兆意义。结果表明:在第Ⅳ活跃幕中,阳江地区ML3地震(去余震)的活跃不仅与本区5级左右地震活动有关,还与东南沿海地震带5级以上强震活动有关,震前阳江地区ML3地震滑动3月频次出现升高现象,阳江地区ML3地震活动可作为东南沿海地震带的地震"窗口";在东南沿海地震带活跃幕期间,ML4地震发震间隔△T≥300d具有震兆意义,是5级地震的短期或中短期指标,而在平静幕期间,ML4地震的长时间平静并不具备震兆意义,只是区域应力场处于松弛状态下的正常表现。

We studied the two characteristics of the 1V active episodes in seismic belt of Southeast China coast in 20th century. The one is the corresponding relation between the southeast coastal seismic belt and the Yangjiang seis- mic window, the other one is the seismic precursory significance about ME4 earthquakes which wasn＇t occurred for a long time. The results showed that the active of ME3 earthquakes in Yangjiang were affected not only by M5 earthquakes occurred in Yangjiang, but also by M 〉 5 moderate-strong earthquakes occurred in seismic belt of Southeast China coast in 1V active episodes. Before the moderate-strong earthquakes, occurrence frequency of ML3 earthquakes in the slip with every 3 months in Yangjiang raised, so ML3 earthquakes in Yangjing can be as the seismic window in seismic belt of Southeast China coast. In active episodes of seismic belt of Southeast China coast, the occurrence time interval ATe〉300 d of ML4 earthquake was the index of M5 earthquake in short-term or medium-short term prediction. However, ML4 earthquakes weren＇t occurred for a long time, which were normal appearances of the regional stress field in relaxed state. However it wasn＇t the seismic precursory signifi- cance in quiet episodes.