You are in: Home » Publications » Reports » Report 23
Recent Geodynamics of the Earth’s Crust in the Region of Antarctic Station “Academic Vernadsky” due to Results of Tectonomagnetic Investigations
Valentyn Maksymchuk,
Yury Gorodysky, Ihor Chobotok,Valentyna Kuznetsova
Carpathian Branch of the Institute of Geophysics of NAS of Ukraine,Naukova
str. 3-b,
Lviv, 79060 Ukraine
E-mail: depart10@cb-igph.lviv.ua
Abstract
The studying of the tectonic activity in the region of location of “Academic
Vernadsky” station (64°15¢, 65°15¢) is actual since
near the station the large regional deep faults were revealed. The important
feature
of the antarctic station location is that archipelago Argentyne islands lies
in the subduction zone of Eastern-Pacific and Antarctic plates and thus under
influence of intens tectonic stresses.
Tectonomagnetic investigations in the region of the Antarctic station “Academic
Vernadsky” were initiated in 1998. In 2001 and 2002 these works were repeated.
They were aimed at the study of the recent geodynamics of the region, detection
of active deep faults and glacier motion study. The tectonomagnetic method
is based on the study of the anomalous magnetic field temporal variations, caused
by various physical-chemical processes in the Earth’s lithosphere. The
methodology presupposes laying of long-term points and profiles, at which
repeatitive observations of geomagnetic field F are performed at the temporal
interval. In
addition the parameter of DDF- anomalous geomagnetic field F variation is
determined for the period of time between the cycles of observations.
The tectonomagnetic works were carried out over the profile Barñhany-Rasmussen of the length 11 km, on which 7 tectonomagnetic points had been set up and three cycles of observations had been performed. The profile crosses crosswise the strike the main rock-forming complexes in the west-east direction. A mean-square error of the survey was about 0.7 nT.
As a result of these observations were determined that anomalous magnetic field temporal variations (DDF-anomalies) have the values from some few to about 15 nT. The morphology of DDF field have certain regularities, which can be seen for period 1998-2001 and for period 1998-2002 (the total changes), as well. The eastern part of the profile is characterized by rather low positive values of DDF with the extremum +2.6 nT. The DDF of the western part is noticebly more anomalous: from -3,5 nT to –15 nt. Another peculiarity of DDF curves consist in similarity between DDF for 1998-2001 and total DDF.
Evident correlation between the static field DFa and DDF allow us to conclude that observed anomalies DDF may be of double nature: a part of it is a result of magnetzation effect under influence of secular variation, another part may be caused by piesomagnetic effect on account of crust stressed state changes.
By the help of mathematical modelling we made the quantitative evaluations
of observed tectonomagnetic anomalies. Due to these evaluations the Earth’s
crust rocks in the region of archipelago stay under expend horizontal stresses
of sublatitudinal alongation. The values of these stresses variations may
be about several bar per year.
Antarctic Geodesy
About Acrobat/PDF files