Information message about destructive earthquake in the central part of Java Island, Indonesia, on May 26, 2006.

     The destructive earthquake has happened on May 26, 2006 at 22:53 GMT (May 27, 02:53 Moscow time) in the central part of Java Island with М=6.2, which caused numerous victims and damages.
     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 2 0 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).
     Preliminary processing has been done with data from 18 stations, accurate processing - with data 40 stations.
     Fig. 1 presents fragments of records obtained from digital stations Vladivistok (∆ 54.5º), Ulan-Bator (∆ 55.7º), Talaya (∆ 59.7º), Yuzhno-Sakhalinsk (∆ 61.8º), Kurchatov (∆ 64.6º), Borovoe (∆ 69.7º). Fig. 2 presents fragments of records obtained from digital stations Yakutsk (∆ 71º), Petropavlovsk (∆ 73º), Magadan (∆ 75º), Garni (∆ 77º), Arti (∆ 77º), Obninsk (∆ 87º).

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 22-53-57.1 -7.96 110.4  10  40  6.2/195.7/108.5-9 IPC GS RAS (Accurate)
2 22-53-56.7 -8.11 110.25  15  18  6.2/135.4/78-8.5195 IPC GS RAS (Preliminary)
3 22-53-58.3 -8.03 110.39  10  145  6.4Mw   43 CSEM
4 22-54-01.2 -8.01 110.29  17  122  6.2Mw 6.0/52 43 NEIC (Preliminary)
5 22-53-59.0 -7.94 110.33  10  122  6.2Mw 6.0/52 43 NEIC (Accurate)
  • 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
  • Epicenter
         Epicenter of this earthquake was in 25 km to the South-South-West from Yogyakarta and in 440 km to the East-South-East from Jakarta city (fig.3 presents the map from WEB site of NEIC, USA )

    Figure 3
    Macroseismic manifestations
         Epicenter of this earthquake was located in the region of Yogyakarta city. Hundreds of houses are destroyed in this multi million populated city, infrastructure, electricity and water supply are damaged . Governmental information agency Antara reports, that many state buildings, schools and shops are in ruins. Electricity and communications are cut off. ВВС reports that Yogyakarta airport is closed, because it’s landing field has cracks and airport’s roof is damaged. Rescue works continue on Java Island. By Monday morning official list of victims contained 5115 names. However this list is increasing: because this earthquake totally destroyed approximately 35 thousand living houses and administrative buildings in Yogyakarta city and around it. Nearly 200 thousand people are homeless. State of emergency for three months is announced as a result of this earthquake. Reuters reports that it was entered in force by President of the country Yusuf Kalla. Moreover, Merapi volcano is situated in 30 km from Yogyakarta. It’s activity renewed in the mid of last year and was increasing last months with powerful eruptions of volcano gas and ashes.

    Figure 4

    Figure 5
    Focal mechanism and seismic moment of the earthquake
         Focal mechanism solutions of this earthquake were obtained in NEIC, USA with TMC method with CMT method in Harvard Center, USA. They are presented in table 2 and shown on fig. 6, 7 in stereographical projection (lower hemisphere, waves of compression areas shown in dark color). As one can see these two solutions are close. The motion in origin has happened under the action of compression and expansion forces. One nodal plane is oriented to the North-Eastern direction, another – to the North-Western. Both nodal planes have steep falling angle. The type of motion along both planes is shift, right sided along NP1 plane and left sided along NP2. The value of seismic moment Мо from NEIC data makes 4.1* 10** 18 n*m, the value of moment magnitude - Mw = 6.3; from HARVARD data - Мо=4.2* 10** 18 n*m and - Mw = 6.3 respectively.
    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
    11105315 7926815080175241 8510NEIC
    102779186 76533217618051 9014HARVARD
  • NEIC - National Earthquakes Information Center of US Geological Service
  • HARVARD - Harvard Geophysical Center (USA)

  • Figure 6

    Figure 7


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