The process of attenuation is big rise and fall.The aftershock actions have come through more than twenty years and never clam down.Today, it still have around 4 level earthquakes happen.

• 唐山地震无明显前震，余震持续时间长，衰减过程起伏大，余震活动历经二十余年未平息，至今仍有4级左右地震发生。