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Magnitude 7.6 - KORYAKIA, RUSSIA

2006 April 20 23:25:02 UTC

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Earthquake Details

Magnitude 7.6
  • Thursday, April 20, 2006 at 23:25:02 (UTC)
    = Coordinated Universal Time
  • Friday, April 21, 2006 at 12:25:02 PM
    = local time at epicenter
  • Time of Earthquake in other Time Zones
    Location 61.075°N, 167.085°E
    Depth 22 km (13.7 miles) set by location program
    Distances 195 km (120 miles) NE of Il'pyrskiy, Russia
    645 km (400 miles) N of Nikol'skoye, Komandorskiye Ostrova, Rus.
    675 km (420 miles) SW of Anadyr', Russia
    6330 km (3940 miles) NNE of MOSCOW, Russia
    Location Uncertainty horizontal +/- 4.3 km (2.7 miles); depth fixed by location program
    Parameters Nst=225, Nph=225, Dmin=778.3 km, Rmss=0.93 sec, Gp= 22°,
    M-type=teleseismic moment magnitude (Mw), Version=7
    Source USGS NEIC (WDCS-D)
    Event ID usltbt
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    Earthquake Summary

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  • The following is a release by the United States Geological Survey, National Earthquake Information Center: A major earthquake occurred IN KORYAKIA, RUSSIA about 205 km (125 miles) NE of Il'pyrskiy, Russia or 6330 km (3930 miles) NNE of MOSCOW, Russia at 5:25 PM MDT, Apr 20, 2006 (Apr 21 at 12:25 PM local time in Koryakia, Russia). The magnitude and location may be revised when additional data and further analysis results are available. No reports of damage or casualties have been received at this time. This is believed to be the largest event in this general area since at least 1900.
  • Felt Reports

    About 40 people injured and the villages of Apuka, Khailino and Vyvenka were destroyed. Some buildings and water supply systems badly damaged in the Korf-Tilichiki area. Damage estimated at 55 million U.S. dollars.

    Tectonic Summary

    The Koryakia earthquake occurred in sparsely populated northeastern Russia, directly north-northeast of the Kamchatka Peninsula. The earthquake was in a complicated geological setting where the configuration and interaction of the tectonic plates between northeastern Asia and northwestern North America are poorly understood. Recent models of the tectonic plates in eastern Russia show that the earthquake occurred near the junction of two plates. These are (1) the Okhotsk plate, which includes the Sea of Okhotsk, the Kamchatka Peninsula and northern Japan, and (2) the extreme northwestern margin of the North American plate. Some evidence indicates that a third plate, the Bering plate, may be present and play a role in the regional tectonics, but this plate is poorly defined with uncertain boundaries.

    Geologically, northeastern Russia in the vicinity of the Koryakia earthquake is composed of a sequence of volcanic island arcs that have been attached or accreted to the margin of a continent. In addition, between about 160 and 65 million years ago, sedimentary basins formed in the region and magma intruded the crust and erupted onto it as volcanoes. The boundaries between accreted island arcs are commonly large faults which, under suitable conditions, might be reactivated to cause earthquakes. So many of these old faults formed during the accretion process that it might be difficult to determine which, if any of them broke to cause the Koryakia earthquake.

    Current models of plate interactions in northeastern Russia indicate that the region is being squeezed in a southeast-northwest direction, which causes shortening at a rate that might be only a few millimeters per year. This southeast-northwest direction of long-term shortening is consistent with the focal mechanism of the Koryakia earthquake, which shows that shortening produced thrust movement on faults that are oriented in a northeast-southwest direction.

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    • Preliminary Earthquake Report
    • U.S. Geological Survey, National Earthquake Information Center
      World Data Center for Seismology, Denver

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