TEC IRREGULARITY, SCINTILLATION AND GEOMAGNETIC VARIATIONS ASSOCIATED WITH THE 
28 MARCH 2005 SUMATRAN EARTHQUAKE 
 
 
Alina Marie Hasbi1,2 , Mohd Alauddin Mohd Ali 1,2, Norbahiah Misran1,2 
 
1 Electrical, Electronic and Systems Department, Faculty of Engineering, 
Universiti Kebangsaan Malaysia,Malaysia (alina.ukm@gmail.com,mama@vlsi.eng.ukm.my) 
 
2 Institute of Space Science, Universiti Kebangsaan Malaysia, Malaysia 
  
ABSTRACT 
 
This paper presents the investigation of preseismic effects in the lithosphere 
and ionosphere during a great earthquake of magnitude 8.7 occurred at 16:09 UT 
on 28 March 2005 in North West of Sumatra, Indonesia. In this paper, perturbations 
of ionospheric TEC and scintillation are compared with geomagnetic variations. 
Ionospheric measurements from four ground-based GPS receivers of the Malaysian 
Survey and Mapping Department (JUPEM) and Sumatran GPS Array (SUGAR) networks are 
collected and analyzed during a quiet period beginning from 21 to 30 March 2005. 
Geomagnetic data is collected from a ground-based INTERMAGNET station, located in 
Phuthuy (21.03°N, 105.95°E), Vietnam. The JUPEM GPS receiver data, which are sampled 
at 30 s interval are used to determine the rate of TEC (ROT) and ROTI, defined as 
the standard deviation of ROT. Our results show precursory signatures of the 28 
March 2005 earthquake in the equatorial lithosphere and ionosphere. TEC fluctuations 
as well as pronounced ROT and ROTI exist during the afternoon hours 1-7 days prior 
to the earthquake. TEC fluctuation persisted a day after the earthquake but gradually 
recovered to normal 2 days after the onset. It is found that TEC fluctuations are 
in good agreement with the fluctuations shown in the X, Y and Z geomagnetic field 
measurements. Strong phase scintillation and S4 index, which maximum values are 0.34 
and 1.0 respectively are also present days prior to the seismic event. The presence 
of ionospheric and magnetic field variations detected before the earthquake during 
a quiet period can be considered as signatures of an underground seismic source.