Report about destructive earthquake near the western coast of Java island , Indonesia, on July, 17 2006

     On July, 17 at 08:19 GMT (12:19 Moscow time) the strong destructive earthquake with М=7.2 has taken place near the western coast of Java island, it caused 5 meters height tsunami which caused human victims and destructions.
     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 50 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).
     Preliminary processing has been done with data from 35 stations, accurate processing - with data 39 stations.
     Fig. 1 presents fragments of records obtained from digital stations Ulan-Bator (∆ 56.9º), Hailar (∆ 59.3º), Ala Archa (∆ 59.8º), Yuzhno-Sakhalinsk (∆ 64.2º), Kurchatov (∆ 64.8º). Fig. 1 presents fragments of records obtained from digital stations Borovoe (∆ 70º), Yakutsk (∆ 73º), Petropavlovsk (∆ 76º), Magadan (∆ 77º), Arti (∆ 77º).

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 08-19-22.0 -9.25 107.46  10  39  7.2/146.1/1510-10.5133 IPC GS RAS (Accurate)
2 08-19-27.0 -9.01 107.48  33  35  7.2/146.0/138-8.5165 IPC GS RAS (Preliminary)
3 08-19-22.0 -9.25 107.46  10  39  7.2/146.1/1510-10.5133 IPC GS RAS (Accurate)
4 08-19-27.0 -9.01 107.48  33  35  7.2/146.0/138-8.5165 IPC GS RAS (Preliminary)
5 08-19-23.5 -9.24 107.36  10  84  7.7Mw   82 CSEM
6 08-19-23.5 -9.24 107.36  10  84  7.7Mw   82 CSEM
7 08-19-25.0 -9.33 107.26  10  96  7.7Mw 6.3/15 65 NEIC (Accurate)
8 08-19-30.7 -9.3 107.35  48  95  7.2Mw 6.2/15  NEIC (Preliminary)
9 08-19-25.0 -9.33 107.26  10  96  7.7Mw 6.3/15 65 NEIC (Accurate)
10 08-19-30.7 -9.3 107.35  48  95  7.2Mw 6.2/15  NEIC (Preliminary)
  • 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
         The epicentre of this earthquake was in Indian Ocean at the distance of 220 kilometers to the south from the resort city of Pangandaran (province Western Java, Indonesia), at 225 kilometers to northeast from Christmas Island and in 355 kms to the south from Jakarta (Java, Indonesia) ( fig.3 - map from site of National Earthquakes Inforamtion Center, USA )

    Figure 3
    Aftershock
         This earthquake was accompanied with numerous aftershocks. In accordance with data of Geophysical Survey of Russian Academy of Sciences 46 aftershocks have been registered on July 18, 2006 by 5 p.m.. The strongest of them (М> =5.5) are presented below:
    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
    200621722006-07-17 09:05:19.0-9.77107.914019-6.0/ 125.5-6 South of Java, Indonesia
    200621652006-07-17 09:13:08.0-8.85107.985026-6.3/ 106-6.5 Java, Indonesia
    200621662006-07-17 10:09:13.0-8.8107.937025-6.2/ 115-5.5 Java, Indonesia
    200621672006-07-17 10:44:34.0-8.96107.894018-5.7/ 105 Java, Indonesia
    200621682006-07-17 11:03:17.0-9.21107.554016-5.7/ 115 South of Java, Indonesia
    200621692006-07-17 11:07:35.0-9.36107.744023-6.1/ 135.5-6 South of Java, Indonesia
    200621712006-07-17 11:24:51.0-8.99108.047023-5.5/ 113.5-4 Java, Indonesia
    200621752006-07-17 12:52:12.0-8.84107.833327-5.5/ 104.5-5 Java, Indonesia
    200621772006-07-17 13:53:49.0-9.54108.013317-5.5/ 94.5-5 South of Java, Indonesia
    200621832006-07-17 15:29:05.0-8.75107.213318-5.8/ 85.5 Java, Indonesia
    200621842006-07-17 15:42:05.0-9.36107.734022-5.8/ 95-5.5 South of Java, Indonesia
    200621852006-07-17 15:45:56.0-9.16108.321030-6.2/ 118-8.5 South of Java, Indonesia
    200621862006-07-17 16:09:51.0-9.14108.811028-6.0/ 127.5-8 South of Java, Indonesia
    200621882006-07-17 16:38:41.0-9.37107.723324-5.5/ 124.5-5 South of Java, Indonesia
    200621902006-07-17 19:09:37.0-8.88107.977021-5.5/ 103.5-4 Java, Indonesia
    200621932006-07-17 19:49:35.0-8.94107.944022-5.8/ 135-5.5 Java, Indonesia
    200622002006-07-18 00:15:50.0-9.01108.854030-5.9/ 155-5.5 South of Java, Indonesia
    200622072006-07-18 03:01:46.0-9.15108.93325-5.5/ 94.5-5 South of Java, Indonesia
    200622102006-07-18 04:18:21.0-9.1108.861032-5.9/ 147.5-8 South of Java, Indonesia
    200622142006-07-18 06:51:46.0-9.58107.983316-5.5/ 84.5-5 South of Java, Indonesia
    Macroseismic manifestations
         This earthquake caused 5 meter wave tsunami near the coast of Java Island, Indonesia, and 60 centimeters wave near the Christmas island. More than 300 people have been killed. The most destructive effect was observed in the area of small resort town Pangandaran of Western Java province. Only in this town in accordance with information of crisis center of Ministry of Health of Indonesia 172 persons were killed and 85 missed. More than 77 persons became victims of tsunami in a seaport Chilachap (Central Java province), which is situated at 40 km from Pangadaran. More than 70 persons were missed. Indonesian mass-media reported about numerous victims at the southern coast of the island. The wave caused by the main strike of the earthquake was from one and a half up to five meters in height and has penetrated into territory of the island at the distance of one kilometer. As a result it destroyed thousands of apartment houses there, hotels, restaurants and office buildings. 23 thousand people became homeless. The push with intensity of five MSK was felt in the capital city Jakarta.

    Figure 4
    Figure 5
    Historical records
         The information was downloaded from the site of NEIC, Geological Service, USA. Earthquake has taken place as a result of collision between two tectonic plates - Australian and Sunda. At this part of boundary area the Australian plate moves to north - northeast from Sunda plate with annual drift of approximately for 59 mm. The Australian plate moves under Sunda plate in the region of Java trench, forming a zone of subduction to the south from Java with progressively big depths of origins below Java and to the north from Java. The reported here earthquake has taken place in the low focused parts of this border between the plates, approximately 50 kms to the north from Java trench. The border area between Australian and Sunda plates is seismically very active. By preliminary results the earthquake on July 17, 2006 was similar to the earthquake on June 2, 1994 with magnitude 7.8, which caused 13 meter wave tsunami killing more than 200 people. The earthquake on June 2, 1994 has taken place to the south from Java, approximately 600 kms to the east - southeast from epicenter of the earthquakes on July 17, 2006. The Earthquake on June 2, 1994 also has taken place as a result of collision between these plates at the low focused parts of boundary zone. Another earthquake in this zone has taken place on August 20, 1977 with magnitude 8.3. It happened within the area of Australian plate approximately 1200 kms to the east - southeast from the earthquake on July 17, 2006. It caused 1.5 meter wave tsunami and killed nearly 200 persons. Destructive earthquake with magnitude 6.2 has been registered on May 26 this year near the city Yogyakarta which has happened at the small depth within the boundaries of Sunda plate.
    Focal mechanism and seismic moment of the earthquake
         Focal mechanism solution of the earthquake 17.07.2006 has been calculated with TMC method in NEIC, USA and in Harvard Center, USA and is presented in table 2 and shown on fig. 6-7. Focal mechanism solutions obtained in different centers are identical, and it is very important, they are identical to tsunami generating earthquake, which happened on September 2, 1992 near the coast of Nicaragua. The motion in origin has occurred under the action of the same value compression forces, oriented to the south-southwest direction and expansion forces oriented to the north-northeast direction. One of the nodal plates was latitudinal oriented and had southeast – northwest propagation and steep falling. The type of the motion - uplift. Another nodal plate was laying flat. The type of the motion - thrust. The value of seismic moment Мо from NEIC makes 8.1* 10** 19 n*m, the value of moment magnitude - Mw = 7.2. The value of seismic moment Мо fro Harvard data makes 4.* 10** 20 n*m, the value of moment magnitude - Mw = 7.7. For reference: the earthquake on September 2, 1992 with M=7.2 has happened in Pacific Ocean at 200 km from the coast of Nicaragua, it caused destructive 8 meter wave tsunami, 116 people were killed and more than 68 missed. The material damage has made 20-30 million US dollars.
    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
    51230113 39204297693113 8490NEIC
    51230113 39204297693113 8490NEIC
    551335195 11042891095104 8089HARVARD
    551335195 11042891095104 8089HARVARD
  • NEIC - National Earthquakes Information Center of US Geological Service
  • NEIC - National Earthquakes Information Center of US Geological Service
  • HARVARD - Harvard Geophysical Center (USA)
  • HARVARD - Harvard Geophysical Center (USA)

    • Figure 6
    Figure 7


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