摘要
2004年9月17日阳江M4.9级地震是1969年阳江M6.4级地震发生后至今震级最大的余震之一,该震中区及附近1970年以来至2004年底的九千余次ML1级以上的地震月频次的统计结果显示,本地4.5级以上地震震前短临时段内,ML 1.0级以上小震活动水平增强不明显,但2004年与1986年的地震临震前,ML0.1级以上的微震次数却异常升高;本地4.5级以上地震前3个月至1年左右,b值均处于0.55左右的低值状态。衰减系数H值的计算均大于1,显示本地4.5级以上地震的余震衰减都很快,在较短时间内呈现出孤立型较强的特点。本次4.9级地震作出的震源机制解显示为走滑型,与1969年主震的情况较为类似。
After the M6.4 earthquake occurred in 1969, Yangjiang M4.9 earthquake in 2004 is one of the biggest aftershocks among the 9429 aftershocks （ML≥ 1.0） in the area. The frequency curve shows the seismic activity level didn＇t rise obviously before the M≥4.5 earthquake in a short and imminent time span. But the frequency curves of the microquakes in 1986 and 2004 main shock rise obviously. Before the M≥4.5 0.55. The decay coefficient H of the M≥4.5 earthquakes the b value curve decreased to about earthquakes shows that the frequency of the aftershocks decayed rapidly and that series should belong to the isolated type series in a short time. The focal mechanism of the M4.9 earthquake shows that it belongs to strike slip type that is similar to the M6.4 earthquake in 1969.
出处
《华南地震》
2005年第4期34-41,共8页
South China Journal of Seismology
