GPS Discrimination of Traveling Ionospheric Disturbances from Underground Nuclear Explosions and Earthquakes

ABSTRACT: Various geophysical activities generate characteristic traveling ionospheric disturbances (TIDs),which are detectible using the GPS data from the Global Navigation Satellite System (GNSS). In this paper,numerical third-order slant total electron content (STEC) derivatives of the TIDs from the 2006 and 2009 NorthKorean underground nuclear explosions (UNEs) are compared to the STEC derivatives of the TIDs from the 2011Japanese Tohoku earthquake. The amplitude spectra of the STEC derivative waveforms from the earthquake havesignificantly lower frequency components than those from the UNEs. In addition, a correlation analysis found thatthe phase differences between the earthquake and UNE waveforms were much greater than those between thewaveforms of the UNEs. Thus, the TIDs induced by the two different events may be readily discriminated on thebasis of their distinctive spectral properties. Copyright # 2014 Institute of Navigation. INTRODUCTIONGPS observations from GNSS receivers havenumerous navigation, engineering, and scienceapplications that include monitoring and modelingEarth’s ionosphere and troposphere. The ionospherehas been studied for not only space weatherconditions, but also to detect and analyze globaland local disturbances (or excitations) from natural(e.g., volcanic eruptions, earthquakes, geomagneticstorms) and man-made (e.g., chemical and nuclearexplosions) geophysical phenomena. For example,Hafstad and Tuve [1] provided direct evidence thatgeomagnetic storms cause perturbations of theionospheric F layer [2]. Accordingly, since the1970s, publications on the Total Electron Content(TEC) observations using satellites have beensteadily increasing in number [2]. Mendillo andKlobuchar [3] noted the positive correlationsbetween geomagnetic storm-induced changes in themaximum electron density of the F2 layer andchanges in the TEC of the ionosphere.In addition to geomagnetic storms, earthquakes,tsunamis, explosions at, above, and below groundlevel, and other geophysical activities disturb theionosphere, especially the distribution and thedensity of electrons. Leonard and Barnes [4]observed ionospheric disturbances triggered by thegreat Alaskan earthquake of 1964. Subsequently, anumber of researchers have investigated thepractical impact of earthquakes on the ionosphere.Zaslavski et alia [5], for example, studied the TECmeasurements from the TOPEX-POSEIDONsatellite signals above active seismic regions, andconcluded based on the statistics from 700earthquakes that monitoring TEC variations canassist is detecting earthquakes. Artru et alia [6]and Occhipinti et alia [7] detected ionosphericwaves induced by a tsunami. Drobzheva andKrasnov [8] developed a set of equations to modelthe atmospheric and ionospheric propagation ofacoustic pulses induced by a chemical explosionon the ground. In addition to showing that theacoustic pulses reached the ionosphere, they foundthat the maximum altitude of propagated signaldid not depend on the size of explosion. Mikhailovet alia [9] investigated ionospheric disturbancesbetween the E and F layers detected by theINTERCOSMOS satellite due to the undergroundnuclear explosion at Novaya Zemlya Island of 24October 1990.