ABSTRACT: The problem of ionospheric variability is regarded from the point of view of spatial and temporal correlations between the GPS TEC variations derived from the neighboring GPS receiver records. It is demonstrated that the technique of the spatial correlation coefficient developed earlier to reveal the ionospheric variations induced by seismic activity sometimes is not very reliable. The new index of the local ionospheric variability is proposed describing the spread of GPS TEC within the given area. It is tested for periods of geomagnetic disturbances and periods of several days preceding the strong (M ⩾ 6) earthquakes occuring within the area of GPS receiver’s network. It is shown that the new index is a promising indicator of the earthquake preparation process, it increases few (5–10) days before the seismic shocks and comes back to normal state after the earthquake. During the periods of increased geomagnetic activity the index does not show such variability.
Advances in Space Research 05/2013; · 1.18 Impact Factor
ABSTRACT: We studied six different parameters derived from three different radiophysical techniques used to monitor area over the central Italy around the time of L'Aquila M6.3 earthquake of 6 April 2009. Namely VLF monitoring, ground based ionospheric sounding and GPS vertical TEC. The parameters derived from these data are: variations of amplitude of VLF signal on different propagation passes, critical frequency foF2 variations, cross-correlation coefficient for different pairs of ground based ionosondes, vertical GPS TEC time series, local variability index for the network of GPS receivers, and GPS TEC map. High congruence of techniques in time and space is found.
General Assembly and Scientific Symposium, 2011 XXXth URSI; 09/2011
Advances in Space Research. 01/2007; 39(5):970-977.
ABSTRACT: This work describes results from our analysis of: (1) GPS Total Electron
Content (TEC) measurements collected from ground based stations; (2)
ionospheric electromagnetic plasma measurements from the DEMETER
satellite; (3) thermal infrared (TIR) data (NOAA/AVHRR, MODIS); (4)
emitted long-wavelength radiation (OLR) and; (5) surface latent heat
flux (SLHF) from NOAA/NCEP. We found atmospheric and ionospheric
anomalies approximately one week prior for both the Dec 26, 2004, M 9.0
Sumatra-Andaman Islands and the March 28, 2005, M 8.7 Northern Sumatra
earthquakes. There were 125 earthquakes (M>5.5) in the 118 days of
data (December 1, 2004 through April 1, 2005) we analyzed in this region
(0°-10°, N and 90°-100° E). Ionospheric variations
(GPS/TEC), associated with the Northern Sumatra events, were determined
from data of both the regional SuGAr array (13 stations in Indonesia)
and four IGS stations. For each station a time series of the vertical
TEC (VTEC) data were computed and compared with the magnetic Dst index,
to see if these signals were the result of external magnetic field
activity. On December 22, four days prior to the M9.0 quake, GPS/TEC
data reached a monthly maximum with low Dst values. For the M 8.7 March
28 earthquake values of GPS/TEC were observed to increase four days
(March 22-25) prior to the event again with low Dst values. The VLF/ICE
instrument on DEMETER was operational during the M 8.7 earthquake of
March 28, 2005. Our analysis shows intensive ELF emissions within the 0
-200 Hz window at the conjugated points on 22 of March, 2005, 6 days
before the earthquake during DEMETERs close proximity to the epicenter.
In the case of the Dec 26, 2004, M 9.0 quake, OLR data were >80 W/m2,
corresponding to approximately two sigma above the mean for the months
of December, between 2001 and 2004, were found on December 21, 2004,
five days before the event. Anomalous values of SLHF associated with the
M9.0 Sumatra-Andaman Islands earthquake event were found on Dec 7, 2005
(above five sigma) and Dec 22, 2005 (SLHF +280Wm2). Smaller anomalies
are also seen on Mar 23, 2005 (SLHF +180Wm2). The anomalies consistently
occur over regions of maximum stress (along continental boundaries), and
appear not to be atmospheric due to the long persistence over the same
AGU Fall Meeting Abstracts. 11/2006; -1:08.
ABSTRACT: The problem of ionospheric variability is regarded from the point of view of spatial and temporal correlation between the GPS TEC variations derived from the neighbor GPS receivers records. It is demonstrated that the technique of the spatial correlation coefficient developed earlier to reveal the ionospheric variations induced by seismic activity sometimes fails. The new index of the local ionospheric variability is proposed describing the spread of GPS TEC within the given area. It is tested for periods of geomagnetic disturbances and periods of several days preceding the strong (M ≥ 6) earthquakes happened within the area of GPS receiver’s network. It is shown that the new index is a good indicator of the earthquake preparation process, it increases few (3-7) days before the seismic shocks and comes to the normal state after the earthquake. During the periods of increased geomagnetic activity the index does mot show such variability.
Proceedings of the 6th International Conference “PROBLEMS OF GEOCOSMOS”, St. Petersburg, Petrodvorets May 23–27, Sankt-Petersburg; 01/2006
ABSTRACT: The paper examines the possible relationship of anomalous variations of different atmospheric and ionospheric parameters observed around the time of a strong earthquake (M<sub> w </sub> 7.8) which occurred in Mexico (state of Colima) on 21 January 2003. These variations are interpreted within the framework of the developed model of the Lithosphere-Atmosphere-Ionosphere coupling. The main attention is focused on the processes in the near ground layer of the atmosphere involving the ionization of air by radon, the water molecules' attachment to the formed ions, and the corresponding changes in the latent heat. Model considerations are supported by experimental measurements showing the local diminution of air humidity one week prior to the earthquake, accompanied by the anomalous thermal infrared (TIR) signals and surface latent heat flux (SLHF) and anomalous variations of the total electron content (TEC) registered over the epicenter of the impending earthquake three days prior to the main earthquake event. Statistical processing of the data of the GPS receivers network, together with various other atmospheric parameters demonstrate the possibility of an early warning of an impending strong earthquake.
Applied Physics. 01/2006; 24(3):835-849.
Geofisica Interntional. 01/2005; 44(4):369-377.
ABSTRACT: In this paper we focus on the variability of electron concentration in the ionosphere measured by ground based ionosondes and GPS receivers around the time of strong earthquakes. It has been detected and statistically proven that several days before the seismic shock the level of this variability increases at the station closest to the epicenter, a fact which can be regarded as precursory phenomenon. More precisely the localness of this specific kind of ionospheric variability is used for the correlation analysis of data of several observation points. The similarity of geographical location of the observation points leads to the similarity of ionospheric variations registered at these sites during both quiet and disturbed geomagnetic conditions, except in the case of those located at the seismoactive zone. As a rule, the local anomalies in the F2 layer and TEC accompanying the preparation of strong earthquakes show themselves in the breaking of the mutual correlation of the critical frequencies f<sub>o</sub>F2 or TEC between stations situated in and outside the seismic zone. The precursory phenomenon appears 1 to 7 days before the time of the seismic shock.
ABSTRACT: En la actualidad se encuentra bien establecida la existencia de variaciones ionosféricas anómalas asociadas con el proceso de preparación de sismos fuertes (M>5). Con el fin de comprobar posibles variaciones ionosféricas que estuvieran relacionadas con el reciente temblor de Colima, México, M=7.8, del 21 de enero de 2003, se analizaron los datos de 5 receptores GPS de la red del Instituto Nacional de Geografía, Estadística e Informática (INEGI) de México. Se encontró que el TEC obtenido a partir de estos datos muestra anomalías importantes de dos a tres días antes del impacto sísmico, mientras que el coeficiente diario de correlación cruzada calculado para diferentes pares de receptores GPS presenta una caída importante dentro de un intervalo de uno a cinco días antes de dicho impacto. Por otra parte, la distribución horizontal (latitud-longitud) de las desviaciones del TEC con respecto a la media mensual para el día y la hora del sismo tuvo su máximo en un punto cercano a la proyección vertical en la ionosfera del epicentro del mismo. Hemos concluido a partir de esto que las variaciones observadas en la ionosfera durante el proceso de preparación y de realización del sismo pueden ser consideradas como posibles precursores de corto plazo del mismo.
Geofísica internacional, ISSN 0016-7169, Vol. 44, Nº. 4, 2005, pags. 369-377.