近场震级起算函数确定与爆炸余震震级计算

The Calculation of Calibration Function and Explosive Aftershocks at the Near Field

在天然地震背景下 ,由于现有的起算函数在 0～ 5km范围内是一个常数 ,因此 ,对于震源深度较浅的小地震震级的测定遇到了困难 ,本文通过理论计算和爆炸地震波实际测量两种方法 ,确定了近场 0～ 5km范围内的震级起算函数。用本文确定的震级起算函数计算了两次爆炸余震序列事件的震级 ,绝大多数的余震震级非常小 ,主要分布在 - 0 5～ 1 0级之间 ,余震序列的M t图与一般强余震M t图明显不同 ,它不仅存在反映较大震级的正向柱状线 ,而且还存在反映较小震级的负向短柱状线。

The calibration function is used for calculating magnitude at the near field that is the constant,therefore,magnitude calculation of small earthquakes encounters vital difficulties.According to the attenuation law of explosions and the propagating theory of elastic waves,the calibration function from 0km to 5km have been obtained.Magnitudes of two aftershock sequences are calculated.Explosive earthquakes have rather small magnitudes.Magnitudes of 90% aftershocks range from -0 5 to 1 0.The M t drawing of explosive aftershocks completely different from that of strong aftershocks.It not only shows lines with positive bar but also short lines negative bar.