唐山地震的重力异常

GRAVITY ANOMALY OF TANGSHAN EARTHQUAKE

摘要:

多年来的工作实践及实验证明了重力仪格值随温度变化而改变,而且对观测值的影响极大,以致造成虚假异常。
本文对京津唐地区重力资料进行格值改算,再计算唐山地震前,唐山测点自74年4月至76年3月累积重力上升了130微伽,由76年3月到7月短期异常近200微伽。
根据异常范围、形态、量值计算震前在莫氏界面断裂处有一个密度异常区。

Abstract:

The practice and experiments for many years have proved that the calibration of the gravimeter varies with temperature and has great effect on observed values. So it is necessary to find the temperature coefficent of the calibration and to correct the calibration of the observation data.
In this article, the calibration of all gravity data in Beijing, Tianjin and Tangshan regions has been corrected in another way. After the correction, the annual variation of gravity values at various stations is obviously eliminated, and has been calculated pre-earthquake gravity anomaly in Tangshan.
From April, 1974 to March, 1976, the cumulative gravity increased by 130μgal and the short-term anomaly approached 200μgal.
The obtained results show that. the pre-earthquake gravity variation may due to the density anomaly at deep levels of the earth's crust.