The diurnal variation of GPS-TEC data recorded at the low-latitude station Agra (Geograph. lat. 27.2°N, long. 78°E) has been analyzed for a period of 9 years between 2007 and 2018 to examine whether the ionospheric perturbations are caused by low-magnitude earthquakes (M < 5) and if so, what may be the spatial scales of perturbations in such cases. The results show that low-magnitude earthquakes also cause perturbation and the spatial scales of perturbation are large varying between 1000 and 2000 km, much higher than those given by Dobrovolsky et al. (Pure Appl Geophys 117:1025, 1979) relation. The profile factor (P-factor) analysis has been introduced to identify earthquake-induced anomalies from those produced by magnetic storms. It is found that the P-factor increases with increasing magnitude of earthquakes from M = 4 to M = 6 and then decreases. The results show that turbulent variations occur in the months of large earthquakes as precursors with periods decreasing with decreasing magnitude of earthquakes. This result is interpreted in terms of excitations of atmospheric gravity waves (AGW) over the epicenters of earthquakes.

在2007年至2018年的9年中，对低纬度地区阿格拉（地理纬度27.2°N，纬度78°E）记录的GPS-TEC数据的日变化进行了为期9年的分析，以检查电离层扰动是由低强度地震（M  <5）引起的，如果是这样，那么在这种情况下，扰动的空间尺度可能是什么。结果表明，低震级地震也会引起扰动，扰动的空间尺度在1000至2000 km之间变化很大，远高于Dobrovolsky等人给出的扰动范围。（Pure Appl Geophys 117：1025，1979）关系。引入了廓线因子（P因子）分析，以从磁暴产生的异常中识别出地震诱发的异常。发现P地震因子从M  = 4到M  = 6随地震强度的增加而增大，然后减小。结果表明，在大地震的前几个月中，湍流发生变化，其前兆随地震幅度的减小而减小。根据地震震中大气重力波（AGW）的激发来解释这一结果。