Abstract: From the near-field observation of microearthquakes and available data,it can be found that the amplitude of displacement decreases with the epicentral distances. The analysis of S-wave spectrum in the digital records indicates that the Goner frequenty is as high as up to 21.9 Hz, with its maximal power spectrum ranging form 0.5-26 Hz, and that the distribution of seismic intensity,epcentral intensity and the longth of major axis of isoseismic line shows certain dispersion,which results from the effect of the near-field surface. Study of these characteristic effect in question can provide a base of earthquake-proof/resisting engineering for economic construction.

Key words: seismological observation, Eqicentral intensity, seismic wave attenuation, Shallow earthquake, Sanxia area

摘要： 通过对三峡地区小台网地震观测和资料研究,认识到该区弹性波地动位移振幅随震中距增加而衰减的变化偏大,地震数字记录的S波波谱分析表明其拐角频率高达21.9Hz,功率谱极大区在0.5～26Hz间,该地区的地震烈度、震中烈度和等震线长轴长度分布具有一定的离散性。上述现象属于极浅源地震波的近场地表效应。研究这些效应特点,可为国家经济建设提供防震、抗震依据。

关键词: 地震观测, 震中烈度, 地震波衰减, 浅源地震, 三峡地区