Pre-seismic irregular ionosphere and its effect on the Total Electron Content and Scintillations as observed from Kolkata during Nepal Earthquake on 12 May 2015
09 Mar 2019-pp 1-1
TL;DR: In this paper, the authors made a study on total electron content (TEC) and carrier level fluctuations of GNSS satellite data taken with Septentrio receiver at the Institute of Radio Physics and Electronics, Calcutta University, Kolkata during April-May 2015.
Abstract: The pre-seismic anomalous condition in the ionosphere and the electromagnetic perturbations due to seismic activity have been known for a long time. Variations in ionospheric parameters above seismically active regions are one of most actual reasons of these perturbations. It is well established through many research papers that radon is considered as earthquake precursor. Anomalous soil radon (radon 222) fluctuations as a signal of Nepal earthquake in 12 May 2015 have been reported by Argha Deb and his group [1].According to them, radon anomalies on 29April 2015 were mainly observed 13 days prior to the M7.3 earthquake on 12 May in Kolkata, Jadavpur University. With reference to that our study has been made on total electron content (TEC) and carrier level fluctuations of GNSS satellite data taken with Septentrio receiver at the Institute of Radio Physics and Electronics, Calcutta University, Kolkata during April-May 2015. It is found that there is a good correspondence between the Radon emission, abnormal change in total electron content and some intense scintillation behaviour in the signal level of GNSS satellites.
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TL;DR: Fujiwara et al. as discussed by the authors verified the appearance of anomalies in the atmosphere before earthquakes through observation of anomalous transmission of VHF electromagnetic (EM) waves beyond line-of-sight.
Abstract: [1] Appearance of anomalies in the atmosphere before earthquakes (EQs) has been verified, through observation of anomalous transmission of VHF electromagnetic (EM) waves beyond line-of-sight. Anomalous increase of the received intensity for a few minutes - several hours on a day was identified by the previous 15-day running median and its inter-quartile range. The cross-correlation between the EQ occurrences and the anomalies shows that the appearance of anomalies was significantly enhanced within 5 days before M � 4.8 EQs. The one-day average number of the anomaly appearance within 5 days was found 2.4 times larger than that of other days. Through the polarization measurement of the received EM waves, the anomalies were found to occur in the atmosphere. INDEX TERMS: 6904 Radio Science: Atmospheric propagation; 6964 Radio Science: Radio wave propagation; 7223 Seismology: Seismic hazard assessment and prediction.Citation: Fujiwara, H., M. Kamogawa, M. Ikeda, J. Y. Liu, H. Sakata, Y. I. Chen, H. Ofuruton, S. Muramatsu, Y. J. Chuo, and Y. H. Ohtsuki (2004), Atmospheric anomalies observed during earthquake occurrences, Geophys. Res. Lett., 31, L17110,
76 citations
TL;DR: In this paper, the authors deal with pre-seismic soil radon-222 recorded at two different locations 200 m apart, at Jadavpur University main campus, Kolkata, India.
Abstract: The present paper deals with pre-seismic soil radon-222 recorded at two different locations 200 m apart, at Jadavpur University main campus, Kolkata, India. Solid state nuclear track detector method is used for detection of the radioactive radon gas. Two simultaneous 4-month long time series data have been analysed. Anomalous fluctuations in the radon datasets have been observed prior to recent earthquakes in Nepal and eastern India during the monitoring period, mainly, the massive 25th April 7.8 M Nepal earthquake. The simultaneous measurements assist in identifying seismogenic radon precursor efficiently.
25 citations
04 Nov 2015
TL;DR: In this paper, the analysis of GPS based TEC measurement corresponding to 5 earthquakes (M > 6.0) that have occurred in 2009 and 2010 during low solar activity period and quiet geomagnetic conditions is reported.
Abstract: The present paper reports the analysis of GPS based TEC measurement corresponding to 5 earthquakes (M > 6.0) that have occurred in 2009 and 2010 during low solar activity period and quiet geomagnetic conditions. The No. of satellites registering high TEC at low elevation angles is observed prior to these earthquakes. The earthquakes are 1) Loyalty Island (22o36'S, 170o54'E) M-6.6 on 19 January 2009, 2) Izu Island (32o48'N, 140o36'E) M-6.6 on 12 August 2009, 3) Ryukyu Islands (23o30'N, 123o30'E) M-6.7 on 17 August 2009, 4) Haiti (18o24'N, 72o30'W) M-7.0 on 12 Jan 2010, 5) Chile (34o12'S, 71o48'W) M-6.9 on 11 March 2010. To identify anomalous behavior of TEC, we compute interquartile range associated with median TEC so as to get upper and lower bound of TEC variation. The results show occurrence of anomalies in VTEC 1 - 13 days prior to the earthquake. The VTEC shows enhancement for all the earthquakes. Enhancement in No. of satellites registering high TEC at low elevation has been observed prior to earthquakes.
5 citations