| NATO
SCIENCE PROGRAMME
Cooperative Science & Technology Sub-Programme
LINKAGE GRANT N° LG 961302
NATO Scientific Affairs Division, Bd. Leopold III, B-1110 Brussels,
Belgium – fax +32 2 707 4232
SCIENTIFIC
REPORT
Sent January 1999 - Updated July 2006 |
| 1.
PROJECT TITLE |
Modern
methods and tools for active deformation studies in the Baikal
Rift, Russia
|
| 2.
PRINCIPAL INVESTIGATORS |
| (i)
Project Coordinator from a NATO country: |
(ii)
Project Coordinator from a Partner |
(iii)
Other Principal Investigators |
Surname/First Names(s)/Title:
DEVERCHERE Jacques, Assitant
Professor
Institute and Address:
UMR 6526 Géosciences Azur
Université P. et M. Curie
Place N. Copernic, 29280 Plouzané, France |
Surname/First Name(s)/Title :
LEVI Kirill G,
Institute and Address:
Institute of the Earth's Crust, Russian Academy of Sciences
Siberian Branch, Lermontov st., 128 - 664033 IRKUTSK, RUSSIA |
Surname
First Name(s) :
CALAIS Eric LUKHNEV Andrei MELNIKOVA ValentinaOUILLON Guy SAN'KOV
Vladimir KOULAKOV IvanPETIT Carole LESNE Olivia RADZIMINOVITCH Natalia |
| 3.
Abstract of the work accomplished and the results obtained
|
| The
aim of this project was to promote within two years an efficient
transfer of recent analytical methods towards Russian teams, all
related to strain and stress near large active faults, and apply
this approach to the Baikal rift, a region characterized by large
faults (~100-150 km) and located just north of Mongolia, place of
active compressional tectonics and very large recent earthquakes. |
|
A.
Seismic tomography and earthquake relocation (J. Deverchère,
V. Melnikova, C. Petit, I. Koulakov)
As initially planned in the NATO Project, we have extracted as
much informations as possible from teleseismic and local earthquake
traveltimes gathered together (about 1700 events), leading to
important conclusions on the deep mantle and crustal structures
of the Baikal rift which contradict previous results from U.S.
teams (see PUB. 2). We have installed the Hypoinverse routine
for relocation on the PC computers in Irkutsk, and have made effective
a general procedure for depth estimations of events in the Baikal
area, by doing: 1. a selection of stations; 2. a selection of
phases; 3. a test of influence of initial depths, Vp/Vs ratio,
and velocity models. This procedure already provides benefits
to the routine work of seismologists in Irkutsk, and will be improved
in 1999 thanks to a stay of N. Radziminovitch in France (French
Ministry of Foreign Affairs). Another paper using depth relocations
will be submitted soon (Earthquake depth distribution in the Baikal
Rift, by J. Deverchère, V.I. Melnikova, N. A. Giliova,
N.A. Radziminovitch, and V.A. San'kov, Geophys. Res. Lett.).
B.
Statistical analysis of russian earthquake catalogue
(G. Ouillon, V.A. San'kov)
We have prepared in Irkutsk a relevant database of more than 100,000
earthquakes for multiscale analysis. First we have tried to estimate
the relationship of the K energy index given by Russian catalogues
with the moment magnitude for shocks of magnitude larger than
5 : there were unfortunately too few (and inaccurate) data for
such an estimation, as the K value was rounded to the closest
integer till 1987. The Baikal rift zone has been divided into
16 zones of 100 by 100 km. We performed a multifractal analysis
of the spatial patterns of seismic activity within each zone (the
catalog contains all events with M>1.7 from 1/1/1987 to 12/31/96).
We have found that the spatial patterns display either a monofractal
behaviour (of fractal dimension of about 1.7) or a multifractal
one, which allow us to define 4 major zones of seismic activity
according to the width of their multifractal spectrum, but which
can not be correlated with the age or size of structures. The
South Barguzin area is a singular one as it does not display any
scaling behaviour. |
This
can be attributed to either its position at a structural node
within the rift, or to a specific position within its own seismic
cycle. We also performed a temporal analysis of the same sub-catalogues
and found that the seismic energy release rate was regular within
each zone, except in the North Barguzin area. The seismic activity
here is temporally much more intermittent. This could indicate
that this zone is close to macroscopic rupture, but this preliminary
« prediction » has to be worked out with more detailed
studies of possible precursors and specific tools. Size distribution
of events (Gutenberg-Richter law) shows great uniformity of
the b-value within the rift, except at its tips for which large
events would be proportionnally more numerous than in other
parts of the rift.
C.
Space Geodesy (E. Calais, K. Levi, A. Lukhnev, V. San'kov, O.
Lesne)
We have first promoted the training of a young Russian scientist,
A. Lukhnev, in GPS data processing: the Lab of Irkutsk is now
able to extract tectonic information from GPS measurements,
and to organize field trips by themselves. In summer 1997, Eric
Calais and Olivia Lesne went in Irkutsk, Russia (1 month), to
perform the third GPS measurement of the Baikal network with
Russian colleagues, under French fundings (MAE/CNRS): 13 sites
are distributed within an area of 250 km by 400 km that covers
the southern part of the region. Four additional geodetic sites
have been installed in 1997 and were measured for the first
time by our Russian colleagues. We processed the GPS data and
computed a final adjustment that takes into account three previous
measurements of this network. The first results are presented
in the common papers listed (PUB. 1 and 3). They represent the
first large-scale measurements of instantaneous velocities in
this large rift system. They show that the southern part of
the Baikal rift is currently opening at a rate of about 4 mm/yr
in a left-lateral strike-slip tectonic regime and depict a velocity
gradient across the rift zone typical for elastic strain accumulation
on locked seismogenic faults. This result gives bounds to models
of deformation of Asia (velocities are higher than model predictions),
and provides a first step towards large rupture forecasting
around Lake Baikal. We have reoccupied part of the network in
summer 1998 (mission of Eric Calais): the results obtained have
been recently processed and confirm the stability of our measurements
over 3 years.
|
Priority
Area: Environmental Security
Award,
in Belgian francs : 900 000,00 BF
Total
income: 139 376 FF
Name
From/To Reason Period from/to
MELNIKOVA Valentina IRKUTSK-NICE - Training
on computing locations and focal solutions from March 1 to March
22, 97
SANKOV Vladimir IRKUTSK-NICE - Partitioning
of the seismic zones of the Baikal rift and seismic tomography
evaluation - from March 1 to March 22, 97
DEVERCHERE Jacques NICE-IRKUTSK - Tests for
procedure of depth relocation of events from July 20 to August
15, 97
OUILLON Guy NICE-IRKUTSK - Processing of the
earthquake catalogue from July 20 to August 15, 97
LUKHNEV Andrei IRKUTSK-NICE - Processing of
GPS data from April 4 to June 13, 98
LEVI Kirill IRKUTSK-NICE - Discussions on fault
kinematic and geodetic results from April 18 to May 4, 98
CALAIS Eric NICE-ULAN BAATAR - Driving GPS
measurement strategy in Russia and Mongolia from July 29 to
August 30, 98
|
Remarks,
if any:
|
Compared to the initial Linkage Grant
Programme proposed, we have only modified the duration of
two stays: Kirill Levi, co-director of the CP country, has
made a shorter stay in France (16 days) for preparing the
discussion of GPS results, while Andrei Lukhnev, young searcher
in the Institute of the Earth's Crust, Irkutsk, in charge
of processing, has prolongated his stay over 70 days (instead
of 1 month), in order to benefit as much as possible from
the good practice of French scientists. Means provided by
NATO appeared convenient for both partners to perform the
work planned in satisfying conditions. This Project has
been a very efficient way to enhance and favor scientific
links between Western and Eastern countries, and to improve
the quality of science between us. We would like to favor
even more than before the promotion of young scientists
from Russia in future Programmes. |
|
| 5.
Publications resulting from the project |
| Nº |
Publications |
| 1 |
Calais,
E., O. Lesne, J. Deverchère, V.A. Sankov, A.V. Lukhnev, A.I.
Miroshnichenko, and K.G. Levi, Crustal deformation in the
Baikal rift from GPS measurements, Geophys. Res. Lett.,
25 (21), 4003-4006, 1998. |
| 2 |
Petit,
C., I. Yu. Koulakov, and J. Deverchère, Velocity
structure around the Baikal rift zone from teleseismic and local
earthquake traveltimes and geodynamic implications, Tectonophysics,
296, 125-144, 1998. |
| 3 |
San’kov,
V.A., K.G. Levi, E. Calais, J. Deverchère, O. Lesne, A.V.
Lukhnev, A.I. Miroshnitchenko, V.Yu. Buddo, V.T. Zalutsky, and Yu
.B. Bashkuev, Present-day and Holocene horizontal movements
in the Baikal testing ground, Russian Geol. and Geophys.
(in Russian), 40(3), 422-430, 1999. |
|