Abstract
<p>Two-dimensional principal component analysis (2DPCA) is implemented to analyze the total electron content (TEC) anomalies after Japan’s Tohoku earthquake that occurred at 05:46 on March 11, 2011 (UTC) (M<sub>w</sub>=9). 2DPCA and TEC data processing were conducted just after this devastating earthquake. Analysis results show an earthquake-associated TEC anomaly near the epicenter that began at 05:47. This may represent an extension of the precursor of the earthquake, to the precursor of China’s Wenchuan earthquake on May 12, 2008, detected by the study of Lin [2012], for which the data were obtained at a height of 150-200 km by the FORMOSAT-3 satellite system. It is impossible that such precursor caused by the acoustic shock waves. Another TEC anomaly near the epicenter occurred at 05:53, and this initiated the propagation of the tsunami effect related to the ionosphere through the acoustic shock waves from the epicenter. However, the TEC anomalies did not appear to be affected by a contemporaneous geomagnetic storm and other non-earthquake effects. The propagation of anomalous fluctuation could be an early warning of the tsunami for the regions far from the epicenter as it began to propagate with the higher speed of 3960-4950 km/h than the tsunami speed (720-800 km/h).</p><div> </div>
Highlights
IntroductionResearch into total electron content (TEC) anomalies associated with earthquakes has been greatly facilitated by the advent of global positioning system (GPS) technology, especially the number of GPS satellites and density of ground receivers [Heki and Ping 2005, Otsuka et al 2006, Kakinami et al 2010, Liu et al 2011, Matsumura et al 2011, Saito et al 2011a, Saito et al 2011b, Tsugawa et al 2011, Khegai et al 2013, Jin et al 2014]
After 05:47, the precursor disappeared quickly because it was slighter weaker than the total electron content (TEC) anomalous fluctuation caused by the tsunami effect
The P-type effects should result in lower temporal and spatial TEC variations caused by slow rock-cracking under stress as compared to those caused by acoustic shock waves [Freund 2003, Liu et al 2011], and it could be detected from the TEC data of the FORMOSAT-3 satellite system with low temporal and spatial resolution [Lin 2012]
Summary
Research into total electron content (TEC) anomalies associated with earthquakes has been greatly facilitated by the advent of global positioning system (GPS) technology, especially the number of GPS satellites and density of ground receivers [Heki and Ping 2005, Otsuka et al 2006, Kakinami et al 2010, Liu et al 2011, Matsumura et al 2011, Saito et al 2011a, Saito et al 2011b, Tsugawa et al 2011, Khegai et al 2013, Jin et al 2014]. Tsugawa et al [2011] and Saito et al [2011b] have investigate TEC maps over Japan for this earthquake event and shown that the TEC variation appeared approximately 7 minutes after the earthquake occurrence. This scenario is reproduced by computer simulations by Matsumura et al [2011]. The Global Differential GPS (GDGPS) System provides a global real-time map of ionospheric electron content. These maps are of value in monitoring the effect of the ionosphere on radio signals, power grids, and on space weather. The integrated electron density data along each receiver-GPS satellite link is processed through a Kalman filter to pro-
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