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| Titel |
Experimental determination of stress variation threshold resulted in earthquake triggering |
| VerfasserIn |
Elena Novikova, Victor Novikov, Vladimir Okunev, Vadim Klyuchkin |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250100276
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| Publikation (Nr.) |
 EGU/EGU2014-16178.pdf |
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| Zusammenfassung |
| There are many field observations of earthquake triggering by static and dynamic stress
variations caused by impact of distant strong earthquakes, underground chemical and nuclear
explosions, solar-lunar earth tides, strong variations of atmospheric pressure etc., as well as
by electric current injection into the Earth crust. It is supposed that the external impacts
on the earthquake source result in exceeding the threshold stress and earthquake
triggering. Nevertheless, the mechanisms of the earthquake triggering phenomena is not
clear, and the problem of determination of stress variation threshold resulted in
initiation of seismic events is very important. At present, based on analysis of field
observations of dynamic triggering of earthquakes (by wave train from distant strong
earthquakes) performed for various regions, including the USA, Japan, China, Greece, etc.
it is considered that the triggering threshold of stress variations is about of 500
kPa.
An experimental study at the spring-slider system was carried out for detailed study of
behavior of fault area under near-to-failure state and experimental triggering impacts, as
well as for determination of the threshold variation of normal stress in the fault
gauge resulted in earthquake (slip) triggering. The spring-slider system provides
a spring loading rate of 0.001 to 0.02 mm/s. The travelling block of dimensions
250x120x65 mm is connected with electromechanical drive via the spring with
9.5 N/mm spring constant. The normal stress of the travelling block is up to 30
kPa. For determination of the triggering threshold of normal stress variations the
electromagnetic system was activated by control system at the level of 0.98-0.99 critical
(fault failure) shear stress, which provided reducing the normal stress (by 0.001% to
0.1%) in the form of rectangular pulses of 0.5 to 5.0 s duration generated in time
interval of 20 to 40 s. The level of stress variation impact resulted in the slip of
travelling block (with stable time delay after the pulse initiation) is considered as the
threshold for the present experimental "stick-slip" system. The measured triggering
threshold of normal stress variations in the fault simulator is 0.05% to 0.10%. An
implication of obtained threshold values for various earthquake mechanisms is discussed. |
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