IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS011 Poster presentation 2134
The investigation of aftershock process of strong earthquakes of the
Eastern-Anatolian fractured zone
Dr. Mariam Mkrtchyan
IAGA ISS011 IASPEI
The Eastern Anatolian fractured zone is one of the seismoactive zones of the Armenian plateau. It
covers folding structures of Eastern Tavros, Bitlis and joints in the area of Lake Van with Zagros belt.
Submeridian seismicity of the Levant fracture from the south adjoins to the Eastern Anatolian zone. The
zone, which is to the south of Tavros is considered to be less active in comparison with Nortern
Anatolian fractured zone. In the past in the given area earthquakes are recorded with the maximal
intensity of no more than M~4.5. But for a short period of time from the seismicity standpoint two
strong earthquakes occured in this area: 22.05.71.; 0:16h44m, φ=38.87N; λ=40.48E, h=22km;
Ms=6.8Bingol area and 06.09.75.; 0:09h20m; φ=38.50N; λ=41.00E; h=26km; Ms=6.7 in Lice to the
northeast of Diyarbakir. The recorded earthquakes as significant seismic events are less studied and an
attempt is made in this work to pay more attention to the investigation of these earthquakes in
particular the aftershock process of earthquakes which had occured in the region are genetically
connected with seismotectonic zone of Erznka seismoactive node and Bitlis zone of fractures. The
aftershocks analysis earthquake 22.05.71. 0:16h44m in the time showed, that the majority of
aftershocks including strong aftershocks occured during the first 24 hours after the main earthquake.
Aftershocks are distributed to the northeast, southwest, at the end of the fault emanated on the
surface. The main earthquake occured nearer to the northwest edge of a fault. The main part of
aftershocks is concentrated here. The strongest aftershock with M=4.8 occured about 2 days later after
the main earthquake, the aftershocks which were nearer to the main shock in time were weaker. The
depth of focuses was 20-25 km. The focal mechanism of earthquakes is left-lateral strike-slip. After the
06.09.75. 0:09h20m earthquake over a period of 31.12.75.- 26 strong aftershocks occured with M ≥
4.0. The main shock and aftershocks are distributed in the limit φ=38.5-39.0N; λ=40.50-41.0E. The
mean depth is 25-30km. The focal mechanism of the 06.09.75 earthquake and its aftershocks is thrust
fault. The detailed analysis aftershock process of these earthquakes showed that: - the space
development of aftershock sequence after a strong earthquake is important for the current estimation of
seismic hazard. - the epicenter of the most strongest aftershock is quite near to the epicenter of the
main earthquake. - the focal mechanism of the strongest aftershocks follows the focal mechanism of the
main shock.
Keywords: strongaftershocksmechanism