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Title: A search for precursors of earthquakes from multi-station ULF observations and TEC measurements in India
Authors: Chauhan, Vishal
Singh, O P
Pandey, Uma
Singh, Birbal
Arrora, B R
Rawat, Gautam
Pathan, B M
Sinha, A K
Sharma, A K
Patil, A V
Keywords: Earthquake;ULF anomalies;Total electron content (TEC);Ionospheric precursors
Issue Date: Oct-2012
Publisher: NISCAIR-CSIR, India
PACS No.: 91.30.pd; 94.20.dv; 94.20.Vv
Abstract: Ground based observations have been carried out for ultra low frequency (ULF) precursors of earthquakes at four different stations in India, namely Agra (geographic lat 27°N, long 78°E), Guttu (lat 31.53°N, long 78.75°E), Shillong (lat 25.92°N, long 91.88°E) and Kolhapur (lat 16.40°N, long 74.15°E) using identical 3-component search coil magnetometers (f = 0.01-30 Hz) obtained from Lviv Centre of Space Research, Ukraine. An offline analysis of the combined data has been carried out in relation to a major earthquake of magnitude M=7.9 occurred in the neighbouring country China (lat 31°N, long 103.32°E, depth=19 km) under the National Program of Earthquakes Precursors (NPEP) launched in India since May 2009. The results of the analysis show occurrence of amplitude anomalies as precursors whose amplitudes decrease with distance. The precursor periods range between 2 and 5 days and are large for the stations nearer to epicenter. A graphical determination of location of the epicenter has been found to be satisfactory with errors within 20.5%. Further, the total electron content (TEC) data obtained from a dual frequency GPS receiver at Agra station and global ionospheric maps (GIMs) of TEC corresponding to the Wenchuan earthquake have also been analysed. The GIM TEC data have been analysed for five different locations which lie between Agra and the epicenter of the earthquake. The anomalies in TEC data are investigated by using quartile based statistical process. It has been found that GPS and GIM TEC data show anomalous depletions of 02 - 13 days before and anomalous enhancements of 03 - 10 days prior to the occurrence of earthquake.
Page(s): 543-556
ISSN: 0975-105X (Online); 0367-8393 (Print)
Appears in Collections:IJRSP Vol.41(5) [October 2012]

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