Information message about destructive earthquake near the western coast of Honshu Island, Japan, July16, 2007

     The destructive earthquake with M=6.7 has happened on July 16, 2007 at 01:13 GMT (05:13 Moscow time) near the western coast of Honshu Island, Japan. This earthquake caused victims and destructions and originated tsunami with 50 cm wave height.
     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 55 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).
     Preliminary processing has been done with data from 28 stations, accurate processing - with data 41 stations.
     Fig. 1 presents fragments of records obtained from digital stations Vladivostok (∆ 7.6º), Hailar (∆ 18º), Petropavlovsk (∆ 20.8º), Yakutsk (∆ 25.1º), Seimchan (∆ 26.8º). Fig. 2 presents fragments of records obtained from digital stations Talaya (∆ 28.3º), Bilibino (∆ 34.3º), Tiksi (∆ 34.5º), Kurchatov (∆ 43.8º), Borovoe (∆ 48.6º).

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 01-13-23.3 37.55 138.6  33  41  6.7/186.6/167.5-897 IPC GS RAS (Accurate)
2 01-13-24.0 37.57 138.42  33  28  6.7/106.6/127.5-897 IPC GS RAS (Preliminary)
3 01-13-27.3 37.55 138.44  60  671  6.6Mw   31 CSEM
4 01-13-27.8 37.58 138.38  49  165  6.7Mw 6.5/98  NEIC (Preliminary)
5 01-13-28.7 37.57 138.44  55  280  6.7Mw 6.4/179 25 NEIC (Accurate)
6 01-13-20.0 37.5 138.6  10    6.6    JMA
  • 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
  • JMA - Japan Meteorological Agency
    • Epicenter
         Epicenter of this earthquake was located in Japanese Sea, 60 km to the south-west from Negate city, 100 km to the north-north-east from Nagano city, 840 km to the south-east from Vladivistok city. This earthquake has happened in highly seismic active region and it’s origin zone is located in the area, where the series of strong earthquakes have occurred on October 23, 24, 27 and on November 08, 2004 with М=5.5-7.0. These earthquakes were also destructive ( Information message about destructive earthquake at the western coast of Honshu Island on October 23, 2004 ). The strong earthquake also has happened in 1964 in the region of Niigata Prefecture with М=7.5 and it’s aftershocks led to 26 victims. Location of the reported earthquake is shown along with know seismic activity from data of Geological Service of USA, NEIC (fig. 3).

    Figure 3
    Aftershock
         This earthquake was accompanied with aftershocks, the strongest of them has been registered by GS RAS with magnitude М=5.7
    N Date   &   Time (GMT)
    yy-mm-dd hh:mm:sec    		 Lat
    degr.    		 Lon
    degr.    		 Depth
    km    		 N
    station    		 Ms/ N mb/ N Io
    calc.    		 Region
    200726372007-07-16 06:37:40.037.57138.5633345.7/ 125.9/ 146-6.5 Near west coast of Honshu, Japan
    Macroseismic manifestations
         The powerful underground shock created disastrous zone in the Japanese cities located at the western coast of Honshu Island in Niigata and Nagano prefectures. The number of victims reached 700 people, seven of them were killed. Energy company "Tokyo Denriku " reported about automatic shutdown of three nuclear power units in Kasividzaki town, which is located in the zone of most significant shocks (fig.4-5). This earthquake originated insignificant tsunami waves with 50 cm height.

    Figure 4
    Figure 5
    Focal mechanism and seismic moment of the earthquake
         Focal mechanism solution of this earthquake has been calculated with TMC method in Geological Service of USA, NEIC and it is presented in table 2 and shown on fig. 6. The motion in origin has happened under prevailing compression forces, oriented to the north-west-south-east direction. Both nodal planes have almost the same direction of propagation (north-east-south-west) and almost equal falling angles. The type of motion along both nodal planes - uplift. Averaged value of seismic moment Мо determined in IPC GS RAS from Р-wave spectra obtained at seismic station "Obninsk" (delta 66 degrees) made 1.3* 10** 19 n*m. The value of moment magnitude from these data made Mw = 6.7. The value of seismic moment Мо in accordance with NEIC made 6.3* 10** 18 n*m, the value of moment magnitude - Mw = 6.5.
    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
    852724134 344228429541 4986NEIC
  • NEIC - National Earthquakes Information Center of US Geological Service

    • Figure 6


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