Information message about the earthquake on May 25, 2001 near Iturup island (Kurilsk islands)

     On May 25, 2001 at 04:40 Moscow time (00:40 GMT) strong and sensitive earthquake (up to 3-MSK) has happened in the south eastern part of Kurilsk islands, near Iturup island.
     Parameters of the earthquake have been determined in the Alert Service (AS) of Information Processing Center (IPC) of Geophysical Survey of RAS in Obninsk with station data obtained from digital and analog seismic stations of Russia, countries of CIS and from abroad. Alert message on this earthquake has been delivered in 60 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).
     Preliminary processing has been done with data from 13 stations, accurate processing - with data 28 stations.
     Figures 1-2 show records from digital stations, obtained in IPC in a close to real time mode.

Figure 1
 

Figure 2
 
     IPC GS RAS also has obtained information with parameters of this event from some seismological centers, these data are given in table 1:
Table 1
NN Time in origin h-min-s (GMT) Lat degr. Lon degr. Depth km N s/st Ms/ N mb/ N I0 calc GAP Center
1 00-40-50.20 44 148  33  28  7.00/156.20/18 IPC GS RAS (Accurate)
2 00-40-48.9 44 148  33  13  6.9/85.0/18 IPC GS RAS (Preliminary)
3 00-40-50.1 44 148      6.9    IPC GS RAS (Sahalin EMSP GSRAS)
4 00-40-49.1 44 148  33  80   6.2   CSEM
5 00-40-50.9 44 148  33  173  6.7/1046.1/73  NEIC
  • IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences
  • CSEM - European - Mediterranean seismological center
  • NEIC - National Earthquakes Information Center of US Geological Service
    • Macroseismic manifestations
         Hypocenter of this earthquake was located in Pacific Ocean near south-western edge of Kurilsk islands (in 105 km to the south-south-east from Kurilsk town of Iturup Island). From data of Sahalin EMSP GS RAS this earthquake wasfelt in South-Kurilsk (Kunashir island) and Kurilsk (Iturup island) – with intensity 5 MSK. No messages have been received about victims or destruction.
    Historical records
         The earthquake on May 25, 2001 has happened in origin region of catastrophic Shikotan earthquake on October 4, 1994 with intensity M=8.4. Current event is located at its north-eastern 8 MSK border. In this origin region seismic activity is registered up now. From data of Geophysical Survey of RAS after the main shock from this event and its strongest aftershock (October 9, 1994 with M=7.6) nearly 500 earthquakes have been registered here with М>=5 and 4 of these events had magnitudes close to 7 (6.9-7.1).
    Focal mechanism and seismic moment of the earthquake
         Focal mechanism of the earthquake 25.05.2001 is typical for the earthquakes of this region (fig.3, lower half sphere). Solution was obtained in Harvard center (USA) from method of moment tensor centroid. Elements of focal mechanisms are given in table 2. As it is seen, both nodal planes have north-western spread direction corresponding with direction of Kurilsk islands. In the motion along the plane with deeper steep (falling angle to horizon 66 degrees) thrust fault was observed, while along the sloping plane (falling angle to horizon 26 degrees) - thrust. Origin of this event occurred as a result prevailing strengths of compression, oriented in north western direction. Seismic moment Mo of this earthquake has been determined in IPC GS RAS from P-wave spectra, registered at 3 seismic stations: Talaya(TLY), Arti (ARU), Obninsk (OBN) located at hypocentrical distances from 30 to 65 degrees. Average value of seismic moment made Mo= 2.2 E 19 n* m, moment magnitude Mw=6.9. From Harvard Center info they made Mo=0.8 E 19 n* m, Mw=6.6.
    Table 2
    Axes of main strengths Nodal planes Center
    T P N NP1 NP2
    Pl Azm Pl Azm Pl Azm Stk Dp Slip Stk Dp Slip
    6727721125 10312322611327 6679HARVARD
  • HARVARD - Harvard Geophysical Center (USA)

    • Figure 3


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