HR: 0800h
AN: GP41A-0830    [Abstracts]
TI: Seismicity and Tectonic Stress Field of the Laptev Sea Shelf
AU: * Koz'min, B M
EM: b.m.kozmin@diamond.ysn.ru
AF: Institute of Diamonds and Precious Metal Geology, Siberian Division, Russian Academy of Sciences, 39 Lenin Prospekt, Sakha Republic (Yakutia), Yakutsk, 677892 Russian Federation
AU: Fujita, K
EM: fujita@msu.edu
AF: Michigan State University, Department of Geological Sciences, East Lansing, MI 48824-1115 United States
AU: Mackey, K G
EM: mackeyke@msu.edu
AF: Michigan State University, Department of Geological Sciences, East Lansing, MI 48824-1115 United States
AU: Imaev, V S
EM: imaev@crust.irk.ru
AF: Institute of the Earth's Crust, Siberian Division, Russian Academy of Sciences, Irkutsk, 664033 Russian Federation
AB: The seismicity of the Laptev Sea shelf, Arctic Ocean, northeast Russia, is primarily concentrated in three north-south to northwest-southeast striking bands that link the mid-ocean Gakkel (Arctic Mid-Ocean) Ridge to the active deformation belts of the Verkhoyansk and Chersky Ranges. The main band extends from Gakkel Ridge to Yana Bay with events of magnitude 5.5-7.0, and is presumed to represent the main boundary between the North American and Eurasian plates. Two zones of weaker seismicity parallel the main band. The West Lena - Taimyr zone follows the western edge of the Laptev Sea shelf and extends from the Lena River delta to Taimyr Peninsula and on to Severnaya Zemlya. Over 300 weak earthquakes have been recorded from this zone with three significant clusterings of events. The first (1980) is located on the east side of Olenek Bay and the second on the west side (1987-1988) faulting). The third cluster occurs on Taimyr Peninsula and had a series of M 4-5 events over the past 50 years. All of these events have a normal faulting to transtensional focal mechanism. The mechanism for the 1990 event (strike 160, dip 63, slip -175) was obtained using Russian regional network data. Geological surveys show that active faults in Taimyr are expressed as linear canyons of northwest to northerly strike with highly fractured rocks. For the 1990 earthquake, this corresponds to normal faulting with a right-lateral strike-slip fault component. The other seismic band is located in the area of the New Siberian Islands and the East Siberian Sea is less considerably less active than the Lena-Taimyr band with only a few dozen weak earthquakes in 60 years. The largest of them (M = 4.9) was a thrust event that occurred in the East Siberian Sea. The two extensional bands are presumed to bound the region of active extension in the Laptev Sea rift system and delineate a Laptev Sea block. The thrusting in the East Siberian Sea may be a result of the reactivation of an old suture zone resulting from ridge induced compression in the adjoining continent.
DE: 9315 Arctic region
DE: 7230 Seismicity and seismotectonics
DE: 8109 Continental tectonics--extensional (0905)
DE: 8150 Plate boundary--general (3040)
DE: 8158 Plate motions--present and recent (3040)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting