Analysis of Seismo-Ionospheric Perturbations using Modified Covariance Algorithm R Revathi 1 , S Lakshminarayana 2 S Koteswara Rao 3 , K S Ramesh 4 , K.Uday Kiran 5 Women Scientist 1 , Professor 2,3,4 , Assistant Professor 5 , K L University, Guntur, Andhra Pradesh, India, e-mail. revathimouni@gmail.com ABSTRACT Earthquakes are the most vulnerable disasters in nature and are inevitable. Electromagnetic detection of earthquakes using Global Positioning System (GPS) has lead to better understanding of our planet earth and related atmospheric systems. In the present work an attempt is made to analyze seismo-ionospheric perturbations for an earthquake which has occurred in Indonesia on 15 th January 2014 with a magnitude of 4.5 on Richter scale. Modified covariance algorithm is applied on the GPS vertical total electron content data taken from the International Global Navigation Satellite System Service station named BAKO It is clearly observed that there is an enhancement of energy in the ionosphere for every 15 minutes from the starting of perturbations. Key words: Seismogenic perturbations, Earthquake, Parametric methods. INTRODUCTION Early detection and prediction of natural disasters such as earthquakes will be of great help to mankind. Identification of percussive signatures of earthquakes is a challenging task for the scientists around the world. Anomalous phenomena in the ionospheric electron density have been observed before many large earthquakes around the world [1],[2]. The dynamic upper atmosphere is perturbed by the anomalous vertical electric field generated in the lower atmosphere, before and during the occurrence of earthquake. This phenomenon is a result of the convective activity of the ion clusters formed in the lower atmosphere. Those ion clusters are formed due to the ionization of the atmosphere near the ground in the epicenter zone of earthquake occurrence [3]. Radon and metal ions are released from the earth’s crust few days before the earthquake occurrence which react with the atmospheric constituents COx , SOx, NOx, and O 2 . This results in the formation of ions and free electrons. The free electrons combine with oxygen, present in the atmosphere, in three body reaction to form negative ions. These ions quickly join with the water molecules, abundantly present in the atmosphere leading to the formation of long living ion clusters. The coulomb’s force of attraction plays an important role in formation of the ion cluste rs of different sizes. The formation of ion clusters in the atmosphere results in release of latent heat. This process leads to the convection of the ion clusters resulting in the generation of the anomalous vertical electric field [4]-[7]. The vertical electric field thus generated will be mapped on to the ionosphere leading to seismogenic perturbations. Global Positioning Systems(GPS) signals traversing though the ionosphere are affected by these perturbations. The variations in GPS signals are measured in terms of total electron content (TEC) as change in the refractive index of the ionospheric medium ,‘n p ’ given by 2 e p )/f n * (40.3 1 n (1) where ‘n e ’ is electron density, ‘f’ is frequency of the GPS transmitted signal. The excess phase delay ‘∆τ p ’ incurred in the signal propagation through the ionosphere is Receiver Satellite p p 1)dl (L) n (1/c) Δτ (2) Land Surface and Cryosphere Remote Sensing III, edited by Reza Khanbilvardi, Ashwagosh Ganju, A. S. Rajawat, Jing M. Chen, Proc. of SPIE Vol. 9877, 987730 · © 2016 SPIE CCC code: 0277-786X/16/$18 · doi: 10.1117/12.2225887 Proc. of SPIE Vol. 9877 987730-1