Information message about series of eahquakes near the Eastern cost of Kamchatka in October 2001

     On October 8, 2001 two strong earthquakes have happened near the Eastern coast of Kamchatka peninsulas. Both of them have happened at 22 hours Moscow time (6pm. GMT) with interval of 6 minutes 08 seconds (the first event has happened at 22-14-26.4, the second at 22-20-34.9), they had equal magnitudes 6.6 and were felt with the same intensity (4 MSK) in Petropavlovsk-Kamchatka town.
     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 14 stations, accurate processing - with data 29 stations.
     Figure 1 contains fragments of records from these two earthquakes at the nearest to hypocenter Petropavlovsk-Kamchatka station (delta=1.0o), figures 2, 3 - contain fragments of records only for the first earthquake at distances of 9 – 70o, which IPC has obtained from digital records in a near to real time mode

Figure 1
 

Figure 2
 

Figure 3
 
     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 18-14-26.40 52 160  50  29  6.60/166.00/136.5-7 IPC GS RAS (accurate)
2 18-14-22.7 52 160  33  14  6.6/115.9/107.5 IPC GS RAS (preliminary)
3 18-14-22.4 52 160  10  328  6.3 5.7-6.3   CSEM
4 18-14-27.18 52 160  55  140  6.3/1185.8/80  NEIC
5 18-14-26.2 52 160  25    6.5    KRIPC
  • 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
  • KRIPC - Regional Informational Processing Center of Kamchatka
    • Epicenter
         Earthquakes have happened near the Eastern coast of Kamchatka peninsular in seismic active zone, in 100 km to the East South-East from Petropavlovsk-Kamchatka town.
    Historical records
         Increase of seismic activity in 2001 in this region has begun since April. According to the data of AS IPC GS RAS since that date 22 events with magnitudes from 3.5 to 6.6 has been registered. The first weak strike has been noticed on April 11 with magnitude 4.2, later rather calm period took place, and since October 5 up today AS processed 14 earthquakes. FIgure 4 presents the map of hypocenters in this region, which is restricted by coordinates 51-53oN and 159-160.5oE, with magnitudes M>=6.0 in the period since 1955 up now. Here one can find hypocenters of 4 strongest earthquakes of this region (M>=7.7-8.5).

    Figure 4
    Focal mechanism and seismic moment of the earthquake
         Focal mechanism parameters of the first earthquake has been determined with TMC method in Harvard Geophysics Laboratory, USA (HRV solution), they are shown in table 2 and figure 5. As it is seen, one nodal plane has close to meridian orientation and rather steep fall, other plane spreads to the North-Western direction and lays much more flat. Thrust push components prevail in motions along both planes, axis of compression is horizontal and spreads almost along the latitudinal direction, axis of expansion is almost vertical and oriented to the North. Values of magnitude from data of Harvard, USA made Mw=6.4. Average value of seismic moment Mo, which has been determined in IPC GS RAS from P-waves spectra, at four seismic stations: Talaya (delta=33.9o), Arti (delta=53.7o), Obninsk (delta=62.9o), (Kislovodsk (delta=69.7o) made 2.1* 10** 19 n*m (2.1* 10**26 D-CM). The value of moment magnitude from these data - Mw=6.8.
    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
    503341886 35189136413022 71127HARVARD
  • HARVARD - Harvard Geophysical Center (USA)

    • Figure 5


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