HOLOCENE VERTICAL MOVEMENTS OF THE KAMCHATKA PACIFIC COAST:
GEOMORPHOLOGIC RECONSTRUCTION AND RELATION TO
SEISMOTECTONIC PROCESSES
Tatiana Pinegina1, Joanne Bourgeois2
Institute of Volcanology & Seismology FED RAS, Petropavlovsk-Kamchatskiy, Russia.
E-mail: pinegtk@kcs.iks.ru
2
University of Washington, USA. E-mail: jbourgeo@u.washington.edu
1
Fig.1
Since 1995 we have been conducting detailed
field studies of the Holocene evolution and
seismotectonic regime of selected areas on the eastern
coast of the Kamchatka Peninsula (Fig.1).
Specific methods of these investigations
include: 1) application of tephrochronology and
tephrostratigraphy [1] for dating and correlation of
various types of coastal deposits and landforms; 2)
study of paleotsunami deposits [4,5,6] in order to
determine their ages and recurrence rate and to estimate
the magnitude of large tsunami and tsunamigenic
earthquakes along the Kurile-Kamchatka subduction
zone and north of the latter during Holocene time (last
10,000 years); 3) analysis of the geologic structure,
age, and modern and paleo-topography of marine
terraces and beach ridges in order to determine the
direction and scale of seismotectonic movements over
different time intervals [2,3].
As a result of these studies we have
reconstructed key events incoastal evolution during the Holocene and determined the ages of
marine accumulative landforms on various segments of the coast. We managed to estimate
coseismic, afterslip and post-seismic vertical deformations for some Kamchatkan historical and
pre-historical earthquakes. Such estimates are feasible in cases where the study area hosts closely
timed volcanic ashes bracketing a strong earthquake.
The shorter the time interval we are able to specify (decades tohundreds of years), the
higher the rate of vertical movements (centimeters totens of centimeters) we tend to obtain.
Estimates of summary deformation for longer periods (hundreds and thousands of years) allow
us to obtain average rates, which are significantly smaller (of the order of 0.1- 1.0 millimetres
per year). A reason for this discrepancy is that a long time interval (thousands of years) normally
includes more than one seismic cycle, and averaging the deformations for such long time
intervals ignores the influence of large-scale individual cycles of vertical movements, each of
which is related to a certain seismic event. Intervals of hundreds of years give intermediate rates
since they include the interseismic phase of relatively slow movements.
This work was support by grants: RFBR # 03-05-64584, 03-05-78027, NSF # EAR
0125787.
References
1. 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.
2. Bourgeois, J.; Ortuno, M.; Thibault, C.; Higman, B.; Pinegina, T. Earthquakes and beach
ridges on Kamchatka\ EGS-AGU-NGS, Nice 2003, EAE03-A-080216.
3. Pinegina, T.; Bourgeois, J. Study of Holocene seismic events along the Kamchatka coast of
the Bering sea, based on paleotsunami deposits and coastal seismodeformations. EGS-AGUEUG Joint Assembly, Nice, France, April 2003, abstract EAE03-A-03138
4. Pinegina T.K., Bourgeois J., Bazanova L.I., Melekestsev I.V., Braitseva O.A., A millennialscale record of Holocene tsunamis on the Kronotskiy Bay cost, Kamchatka, Russia //
Quaternary Research. 2003. V. 59.
5. Pinegina T.K. and Bourgeois J. Historical and paleo-tsunami deposits on Kamchatka, Russia:
long-term chronologies and long-distance correlations. Natural Hazards and Earth System
Sciences. Volume 1, Number 4, 2001 page 177-185.
6. Pinegina T.K., Bourgeus J. Tsunami deposits and paleo-tsunami history on Peninsula
Kamchatskiy (56-57oN), Kamchatka region (Bering Sea), Russia: preliminary report // AGU,
1998.