DESIGN AND CONSTRUCTION OF LONG PERIOD SEISMO-GRAPHS TYPE 768 OF LARGE DISPLACEMENT

In this paper, it is described two sets of seismographs, specially designed and constructed to meet the requirements of telemetered seismic network for recording seismic waves with longer period and larger displacement. They are characterized by longer period, higher sensitivity, multiple recording range, good stability, compact and small size. Due to the adoption of flexural pivot and zero-length spring, the amplitude-period effect as well as the pendulum positionperiod effect are quite small.Experience shows that in order to achieve good results of a long period seismograph, it depends on a large extent on the patience of the instrumental operator in carefully adjusting the system. Thus far these seismographs can be considered as satisfactory in operation, fulfilling all the design criteria initially set.