Geoscience Reference
In-Depth Information
Chapter 10
Ionospheric Quasi-static Electric Field Anomalies
During Seismic Activity
M. Gousheva, D. Danov, P. Hristov, and M. Matova
INTRODUCTION
The chapter proposes new results, analyses, and information for the plate tectonic
situation in the processing of INTERCOSMOS-BULGARIA-1300 satellite data about
anomalies of the quasi-static electric field in the upper ionosphere over activated earth-
quake source regions at different latitudes. The earthquake catalog is made on the basis
of information from the United State Geological Survey (USGS) website. The distur-
bances in ionospheric quasi-static electric fields are recorded by IESP-1 instrument
aboard the INTERCOSMOS-BULGARIA-1300 satellite and they are compared with
significant seismic events from the period August 14-September 20, 1981 in magneti-
cally very quiet, quiet, and medium quiet days. The main tectonic characteristics of the
seismically activated territories are also taken in account. The main goal of the above
research work is to enlarge the research of possible connections between anomalous
vertical electric field penetrations into the ionosphere and the earthquake manifesta-
tions, also to propose tectonic arguments for the observed phenomena. The studies are
represented in four main blocks: (i) previous studies of similar problems, (ii) selection
of satellite, seismic and plate tectonic data, (iii) data processing with new specialized
software and observations of the quasi-static electric field, and (iv) summary, compari-
son of new with previous results in our studies and conclusion. We establish the high
informativity of the vertical component
Ez
of the quasi-static electric field in the up-
per ionosphere according observations by INTERCOSMOS-BULGARIA-1300 that
are placed above considerably activated earthquake sources. This component shows
an increase of about 2-10 mV/m above sources, situated on mobile structures of the
plates. The chapter discusses the observed effects. It is represented also a statistical
study of ionospheric effects 5-15 days before and 5-15 days after the earthquakes with
magnitude M 4.8-7.9.
The study is devoted to statistical data of possible connections between anomalous
ionospheric vertical quasi-static fi elds and the seismic activity. A 3-7 mV/m penetra-
tion in the vertical component in the upper ionospheric quasi-static electric fi elds from
an electrostatic source were observed at fi rst by Chmyrev et al. (1989) on the board
INTERCOSMOS-BULGARIA-1300 satellite 15 min before an earthquake with M =
4.8. Several observations of ionosphere precursors for earthquakes, including those
connected with a perturbation of an electrostatic fi eld in the atmosphere and iono-
sphere was studied by Alperovich et al. (1999) and Kim et al. (1999). One of the most
developed interpretations of these phenomena is based on the electrodynamic model
