ADDTID: An Alternative Tool for Studying Earthquake/Tsunami Signatures in the Ionosphere. Case of the 2011 Tohoku Earthquake

Heng Yang,Manuel Hernández-Pajares,Enrique Monte Moreno

doi:10.3390/rs11161894

Abstract

In this work, we characterized the ionospheric disturbances generated during the Japan Tohoku earthquake of 11 March 2011, by means of the Atomic Decomposition Detector of Traveling Ionospheric Disturbances (ADDTID) algorithm. This algorithm automatically detects and characterizes Traveling Ionospheric Disturbances (TIDs) from Global Navigation Satellite System (GNSS) measurements. Applying the high-precision estimates of ADDTID, the propagation parameters would make it easier to distinguish TIDs from different origins, in particular the characteristics conforming the acoustic gravity waves driven by the earthquake/tsunami. This method does not assume that disturbances follow a circular pattern of propagation, and can estimate the location by the propagation pattern of tsunami wavefronts and related TIDs. In this work, we present in a single framework a description of phenomena observed by different researchers. By means of the ADDTID algorithm, we detect: (a) simultaneous TIDs of different characteristics, where the detection was robust against the curvature of the wave fronts of the perturbations and the accuracy of the estimated parameters. The results were double-checked by visual inspection from detrended Vertical Total Electron Content (VTEC) maps and keogram plots, and the parameters of the slow-speed TIDs were consistent with the tsunami waveform measurements; (b) different wavefronts between the west and east TIDs around the epicenter, consistent in time and space with the post-earthquake tsunami; (c) complete evolution of the circular TIDs driven by the tsunami during the GNSS observable area; (d) fast and short circular TIDs related to the acoustic waves of earthquake; (e) the pre-seismic activity consisting of a set of fast westward TIDs, and the comparison with neighboring days; (f) the location estimation of the tsunami wavefront along the coast and the possible use as early warning. Finally, we report disturbances that had not been previously published with a possible application to local and real-time detection of tsunamis.

Highlights

In this article, we will analyze the relationship between earthquake/tsunami signatures in the ionosphere, in the form of Traveling Ionospheric Disturbances (TIDs)
In the lower row of the figure we present the state of the detrended Vertical Total Electron Content (VTEC) maps at in order to show the physical meaning of the features shown in the keogram, and to understand the intensity, velocity of the initial high-speed disturbances and asymmetries in the propagation
The analysis done by means of the Atomic Decomposition Detector of Traveling Ionospheric Disturbances (ADDTID) consists of the following two items: (a) The description of the disturbances for the duration will be made by means of polar plots and histograms for each element of the grid, i.e., Figure 4 for 04:00–05:45 UT, Figure 5 for 05:45–06:45 UT, Figure 6 for 06:45–07:45 UT, and Figure 7 for 07:45–09:00 UT; (b) The detected disturbances at detrending periods of 60 and 300 s are shown jointly in these diagrams

Summary

Introduction

We will analyze the relationship between earthquake/tsunami signatures in the ionosphere, in the form of Traveling Ionospheric Disturbances (TIDs). The main advantage of this method is that it does a local (in the geographical sense) estimate of the TIDs parameters such as number of TIDs, and provides a detailed time evolution of the azimuth, wavelength, velocity, and period of each TID. This information is not easy to estimate from the detrended Vertical Total Electron Content (VTEC) maps or from the keograms. Because the estimate is done locally, it generates time series of the parameters of the TIDs. the method can characterize the asymmetries in propagation azimuth, wavelength, amplitude, and velocity. In order to evaluate the performance of the algorithm, we will compare the detrended VTEC maps with the estimates given by the algorithm

Objectives

Methods

Results

Discussion

Conclusion