1988年耿马地震部分余震观测

用MCD—3X型测深地震仪改装后加入一个延时触发记录装置的仪器,在耿马Ms=7.2级地震极震区进行观测,记录到一些小余震。定位在IBM—PC计算机上进行。根据定位结果,计算了地震射线的离源角,用观测到的P波初动方向资料在SCHMIDT网上绘制了方向分布图,作出了一组节面。这是一组由北盘向上逆冲滑动为主引起的地震,破裂具有微小的走滑分量,性质为左旋。这个破裂与耿马主震的以右旋走滑为主的破裂完全不同。利用震源机制结果,结合其它资料对发震应力场和发震断裂进行了讨论和研究。

OBSERVATIONS ON SOME AFTERSHOCKS OF THE 1988 GENGMA EARTHQUAKE

The revised seismic sounding instrument MCD-3X, plus a delay trigger recording device, was used in the meizoseismic area of the Gengma earthuake (M = 7.2) and some small aftershocks were observed. The location was made by IBM-PC computer. Based on the location results the off-source angle of seismic ray was calculated, the direction distribution was plotted on SCHMIDT net by observed P wave onset directions, and the nodal plane was suggested. The events were caused mainly by the upthrusting of the north bank of the fault, with a small amount of left-lateral strike-slip. The ruptures were different from that of the Gengma mainshock with a right-lateral strike-slip. Finally, the seismogenic field and seismogenic faulting were discussed by the source mechanism solut'on, in combination with other information.