SEISMOTECTONICS AND EVOLUTION OF SOLDATSKAYA BAY (KAMCHATKA)
DURING THE HOLOCENE
E.A. Kravchynovskaya1, T.K. Pinegina2, Joanne Bourgeois3, Kevin Pedoja4
Moscow State University, Russia. E-mail: katja832003@mail.ru
2
Institute of Volcanology & Seismology FEB RAS, Russia. E-mail: pinegtk@kcs.iks.ru
3
University of Washington, USA. E-mail: jbourgeo@u.washington.edu
4
University of Paris, France. E-mail: pedojak@yahoo.fr
1
In 2003 we conducted detailed research on the
Holocene seismotectonic evolution of Soldatskaya Bay,
Kamchatka. The bay is located between two tectonic
«blocks», which constitute Kamchatsky Mys Peninsula.
The southern block represents a part of the island arc front
and is located at the junction of the Kurile-Kamchatka and
Aleutian arcs [1]. This block is characterized by rapid uplift
(up to 1 cm per year during the Late Holocene) [3, 4]. The
northern block is located beyond the active subduction
zone. It is characterized by rather slow differentiated
movements.
During our paleoseismological research in
Soldatskaya Bay we have found thatthe main factors
influencing its evolution in the Holocene were
differentiated tectonic movements, which have been studied
based on morphology, geological structure and ages of the
beach ridges and marine terraces [2, 4]. Ages of the
coastal landforms have been determined based on
tephrochronology [5, 6]. The resulting direction of tectonic
movements in Soldatskaya Bay during the last 6000
years is positive at an average rate of ~0.1 cm/yr.
Tectonic movements within the interval of 6-4 ka BP
are difficult to assess. We suggest that during this time
some subsidence of the Holocene terrace occurred.
Alternatively, there is some evidence in the North
Pacific for a mid-Holocene highstand. Starting
Soldatskaya
Bay
from ~4 ka BP and up to 1854 the bay has been
experiencing tectonic uplift.
During the period from 1950 BC to 250 AD its average
rate was 0.04 cm/yr; during the period from 250 AD to
590 AD - 0.23 cm/yr; and from 590 to 1854 AD - 0.1
cm/yr. From 1854 to 1964 the bay experienced rapid
subsidence at an average rate of 1.2 cm/yr. As we see,
periods of rapid uplift in Soldatskaya Bay alternated
Cape
Kamchatskiy
with periods of slow uplift or even subsidence. Rates of
tectonic movements were different in south and north
parts of the bay. The time intervals were singled out based on dated tephra layers preserved in
the coastal sections.
The data obtained have allowed us to document not only differentiated tectonic
movements but also large coseismic deformations related to individual strong earthquakes. In
Soldatskaya Bay, abrupt vertical deformations of the surface have resulted in the formation of
numerous beach ridges. The shorter the time interval we choose for our calculations, the larger
the calculated amplitude of the vertical movements. This is explained by the fact that regarding
long intervals, we get an average rate of movements, and are not able to single out individual
seismic events.
Based on seismotectonic studies and field data we have compiled a
paleogeomorphological sketch map of the Soldatskaya Bay coast and adjacent area and
reconstructed key events in its Holocene history.
This work was support by :
Russian Academy of science (grant # 03-05-64584, # 03-05-78027) & National
Scientific Foundation (grant # № EAR 0125787).
References
1.
2.
3.
4.
5.
6.
Avdeiko G.P., Popruzhenko S.V., Palueva A.A. Modern structure of the KurileKamchatka region and magma-forming conditions/ Geodynamics and volcanism of
the Kurile-Kamchatka island-Arc-System. Petropavlovsk-Kamchatski., 2001 (in
Russian).
Kravchynovskaya E.A. The history and development factors of Soldatskaya Bay
(Kamchatskiy Cape Peninsula) in Holocene/ Abstract for International student
conference, Moscow, MSU, 2004 (in Russian).
Melekestsev I.V., Kurbatov A.V., Pevzner M.M., Sulergitskiy L.D. Prehistoric
tsunamis & strong earthquakes at Kamchatskiy Cape Peninsula (Kamchatka) by
tephrohronological studies/ Volcanology & seismology, Vol. 4-5, 1994 (in Russian).
Pinegina T.K. Tsunamies on the Pacific coast of Kamchatka for the last 7000 yr.: the
diagnostics, dating, frequency/ Geodynamics and volcanism of the Kurile-Kamchatka
island-Arc-System. Petropavlovsk-Kamchatski., 2001 (in Russian).
Braitseva O.A., Ponomareva V.V., Sulerzhitsky L. D., Melekestsev I.V., Bailey J.
Holocene key-marker tephra layers in Kamchatka, Russia // Quaternary Research.
1997. V.47.
Pinegina T.K., Bourgeois J., Bazanova L.I., Melekestsev I.V., Braitseva O.A., A
millennial-scale record of Holocene tsunamis on the Kronotskiy Bay cost, Kamchatka,
Russia // Quaternary Research. 2003. V. 59.