宁波台动水位与垂直摆对印尼8.9和日本9.0级地震的同震响应

The co-seismic responses of dynamic water level and vertical pendulum at Ningbo seismic station for the Sumatra M8.9 and Japan M9.0 earthquakes

分析认为宁波台ZK03井动水位与VS垂直摆倾斜仪出现的异常可能是印尼8.9和日本9.0级地震的同震响应。印尼8.9级地震后,动水位表现为地震波引起的脉冲和阶跃变化并抬高水位。垂直摆表现为形变波引起的脉冲和阶跃变化,EW向最大幅度约为408.328×10-3〃的脉冲式向E振荡波,并向W出现阶跃变化;NS向最大幅度约为295.192×10-3〃的脉冲式向N振荡波,并产生向N阶跃变化。日本9.0级地震后,动水位表现为地震波引起的脉冲和阶跃变化,10余小时后水位恢复到震前水平,垂直摆表现为形变波引起的脉冲式反复振荡变化,EW向最大幅度约为304.163×10-3〃的脉冲式向E振荡波;NS向最大幅度约为372.252×10-3〃的脉冲式向N振荡波。分析结果说明,该台垂直摆记录的形变波两分向振幅比明显不同,具有一定的方向性,即近垂直于震中分向的振幅大于近平行分向。动水位和垂直摆记录的正常固体潮形态和异常变化具有相似性。

Based on analyses of the anomalies in dynamic water level and vertical pendu lum tiltmeter at the well no. ZK03 of Ningbo station, the anomalies were known as co--seis- mic responses of the Sumatra 1V/8.9 earthquake and the Japan ./V/9.0 earthquake. For the Su matra M8.9 earthquake, the dynamic water level showed co-seismic pulse and step change to high level; the vertical pendulum showed pulse and step change caused by crustal deformation wave, the amplitude of pulse was about 408.328×10 3,, from west to east in WE direction and the step change was from east to west; the amplitude in NS direction was about 295. 192×10-3＂ from south to north and the step change was from south to north. After the Japan M9.0 earthquake, the dynamic water level showed pulse and step change caused by seismic wave, and recovered to the level before the earthquake after 10 hours; The vertical pendulum showed repeating pulses and the amplitude in WE direction was about 304. 163 × 10 -3, from west to east; and the amplitude in NS direction was about 372. 252× 10-3＂ from south to north, from the above analyses it concludes that the amplitudes of this station in the two directions were obviously different, they showed a direction sense, i.e. , the amplitude perpendicular to the earthquake focus was greater than that parallel to the earthquake focus. The normal tidal changes and the anomalous changes for dynamic water level and vertical pendulum were similar.