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2. PHD Thesis / Tesis PHD
3. Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

Title:	Analysis of ionospheric disturbances before and during earthquakes over Sumatra
Authors:	Alina Marie Hasbi (P34996)
Supervisor:	Zainol Abidin Abdul Rashid, Assoc. Prof. Dr.
Keywords:	Analysis of ionospheric disturbances Ionospheric disturbances Before and during earthquakes Sumatra Ionosphere
Issue Date:	7-Aug-2011
Description:	Seismo-ionospheric coupling research has acclaimed specific attention from the scientific community due to the triggering of disastrous earthquakes that have claimed many lives and properties. However, due to the highly unpredictable behavior of the equatorial ionosphere as well as the lack of measurements over seismically active regions such as Sumatra, this research has often been a subject of debate. The advent of the Global Positioning System (GPS) sensing technology provides exciting prospects in seismology including detecting and analyzing signals in regions of seismic activity. This thesis aims to analyze the ionospheric disturbances during and prior to earthquake events in Sumatra. In order to achieve this objective, the thesis addresses several critical challenges in contributing to earthquake prediction research. First, to investigate the ionospheric disturbances during Sumatra earthquake event in the GPS TEC and geomagnetic field measurements and conduct a correlation between both measurements. Second, to analyze the characteristics of precursory signatures in the ionospheric Total Electron Content (TEC) prior to strong Sumatra earthquake events and validate them using CHAMP satellite electron density measurements. Finally, to perform a long-term statistical analysis of temporal and spatial correlation between irregular TEC and earthquake occurrence using the envelope, crosscorrelation and the TEC variability index techniques. Data between 2004 and 2007 obtained from ground-based GPS stations located surrounding the earthquake epicentres, CHAMP satellite electron density and ground-based magnetometer were employed in the analyses. The study of ionospheric disturbances during earthquakes showed TEC oscillations with horizontal propagation velocities of 900-1200 m/s about 10-24 minutes after the events. The magnetic field measurements show rapid fluctuations of 4-5 seconds shortly after the earthquake, followed by magnetic pulsations about 8-11 minutes after the events. The GPS TEC disturbances and magnetic pulsations were well correlated, suggesting that the acoustic wave generated near the epicentre propagates upwards to ionospheric heights and induce disturbances in the ionosphere. The results prior to earthquakes showed significant TEC increases of up to 88% and decreases of up to 45% with respect to the upper and lower bound, respectively observed within few hours to six days before the earthquakes. These TEC anomalies were detected mostly during daytime and do not only depend on their distances from the epicentre but on their latitude positions in the equatorial anomaly region. This phenomenon is mainly due to the migration of ionospheric anomalies to the direction of meridional winds toward the equatorial anomaly crests and the ExB drift during the daytime. The precursory signatures also appeared in the form of equatorial anomaly modification during a few days before the events. The results also showed that both GPS TEC and CHAMP electron density measurements exhibit similar tendencies. The long-term statistical analysis of GPS TEC showed that anomalous TEC variations are observed prior to large earthquake events but they are also observed prior to non-earthquake periods and are subject to seasonal variations. Therefore, the statistical methods need to be improved in order to better distinguish between earthquake-related signals and non-earthquake related ones. In general, these results have proven the efficiency of joint measurement techniques to detect possible seismo-ionospheric disturbances as well as enhancing the understanding of the physical processes involved prior and during earthquakes. Hence, the results can further be used to improve the efficiency of future earthquake and tsunami warning systems.,PhD
Pages:	218
Call Number:	QC881.2.I6 .A435 2011 3
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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