海原5.5级地震时的倾斜突变

1982年4月14日海原5.5级地震时,周围260公里范围内的六个倾斜台站全部记录到了震时倾斜突变。倾斜突变等值线图为—长轴呈北西—南东向分布的、较规则的椭园形,递减规律明显。震中附近倾斜突变值最大,高值区呈北西—南东向,成条带状,与最内圈等震线长轴方向、地质构造线走向、震源机制解结果一致。因此,反映了震时断层活动情况,可做为推测发震构造的判据之一。

THE TILT STEP IN THE HAIYUAN EARTHQUAKE (Ms=5.5)

During the Haiyuan earthquake(M_s=5.5) the tilt step was observed by six tilt stations in the 260km range around the epicentre. The tilt step isogram was a rather regular ellipse. The direction of long axis of the ellipse was NW-SE. Decrease law of the tilt step value was clear. The value was the greatest near the epicentre. The high value area was a stripe-belt shape that was distributed in the direction of NW-SE and was in agreeing with the long axis of the innermost isoseismal line, the strike of geologic structure lines and the result of the mechanism of the earthquake foci. Therefore, the tilt step is the reflection of fault activities in the earthquake. The high value area can be regarded as a basis for our inference of earthquake fault.