Information message about the devastating earthquake on the coast of central Chile on Feb. 27, 2010.

     Powerful earthquake with M = 8.7, resulting in human casualties and destructions has occurred on February 27, 2010 at 06:34 a.m. GMT (February 27, 09:34 Moscow time) on the coast of central Chile.
     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 31 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).
     Preliminary processing has been done with data from 29 stations, accurate processing - with data 34 stations.
     Fig. 1 presents fragments of records obtained from digital stations Juntas de Abangares (∆ 47.5º), Hockley (∆ 69.1º), Albuquerque (∆ 77.3º), Monasavu (∆ 94.3º). Fig. 2 presents fragments of records obtained from digital stations Obninsk (∆ 129.4º), Lovozero (∆ 129.4º), Kislovodsk (∆ 131.1º), Garni (∆ 131.6º).

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 06-34-16.1 -36.05 -72.8  60  29  8.7/216.7/59.5-10 61 IPC GS RAS (Preliminary)
2 06-34-13.0 -36.04 -72.88  33  34  8.7/216.9/610.5-11 61 IPC GS RAS (Accurate)
3 06-34-16.0 -35.89 -72.778  50  240  8.3 Mw   21 CSEM
4 06-34-17.3 -35.826 -72.669  59  220  8.3 Mw 7.1/190  NEIC (Preliminary)
5 06-34-14.5 -35.846 -72.719  35  255  8.8 Mw 7.1/153 36 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
         Fig. 3 shows with red star epicenter of this earthquake, whose origin was on the coast of central Chile, at a depth of 33 km, 86 km north-northeast of Concepcion and 355 kilometers south-southwest of Santiago, the capital of Chile.

    Figure 3
    Aftershock
         This earthquake was accompanied with aftershocks. GS RAS registered 7 aftershocks with М>=6 within initial four hours after the main shock.
    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
    201007482010-02-27 06:52:34.0-34.71-72.513314-6.3/ 36.5-7 Near coast of Central Chile
    201007492010-02-27 07:37:17.0-36.9-73.093321-6.2/ 36-6.5 Near coast of Central Chile
    201007502010-02-27 08:01:23.0-37.84-75.263325-6.6/ 27-7.5 Off coast of Central Chile
    201007512010-02-27 08:25:28.0-34.82-72.643319-6.1/ 26-6.5 Near coast of Central Chile
    201007532010-02-27 10:10:14.0-33.76-72.473320-6.0/ 46 Off coast of Central Chile
    201007542010-02-27 10:30:34.0-33.77-73.313313-6.0/ 46 Off coast of Central Chile
    201007552010-02-27 10:38:33.0-38.23-73.723311-6.1/ 46-6.5 Near coast of Central Chile
    Macroseismic manifestations
         According to ITAR-TASS by March 2 this earthquake in Chile killed more than 700 people, 300 residents are still missing. This was reported by the country's president Michelle Bachelet. "This is a huge catastrophe," - said the president in his address to the nation. She also reported that the Government of Chile has declared a state of emergency for 30 days in the region of Bio Bio, and Maule, the most severely affected by the earthquake. This earthquake was followed by a series of tsunamis. The waves struck on 11 Chilean cities. On the island of Robinson Crusoe of the Chilean archipelago of Juan Fernandez three-meter wave killed at least five people. In New Zealand the maximum height of waves was two meters. Hawaii was attacked by the wave with 2.3 m height. In the U.S. the highest waves were recorded in Santa Barbara, California - more than a meter. On the coast of Honshu island the wave height has reached 1.45 meters. Maximum rise of water was registered from 30 to 60 cm in some areas from Hokkaido to Okinawa. In accordance with information from Sakhalin center of tsunami a special sensor mounted on the Paramushir island registered secondary wave with 2 meter 20 centimeters height. City of Severo-Kurilsk located on the island was built at a height of 17 meters above sea level, no one was hurt. On Shikotan island the height of residual tsunami wave was 68 cm, on Iturup island it did not exceed 10-15 cm. According to Kamchatka Tsunami Warning Center, the maximum height of tidal waves in southern Kamchatka reached 60-70 cm. According to USGS NEIC this earthquake was felt in Chile, Argentina, Brazil and Peru. Fig. 5 taken from the USGS NEIC presents intensity map composed of telephone calls made by 1159 respondents from 110 localities.

    Figure 4
    Figure 5
    Historical records
         Chilean coast from Point Conception to the island of Chiloe is characterized by the frequent and strong earthquakes. According to the authors "Tsunami: prevention and protection" Y.L. Vorobiev, V.A. Akimov and Y.I. Sokolov since the disaster in 1562 the city of Concepcion suffered 12 strong earthquakes, and the city of Valdivia for the period from 1575 to 1907 - 7 earthquakes. During the earthquake of January 24, 1939 in Concepción and around 1000 people were killed and 70,000 people homeless. May 22, 1960 earthquake devastated parts with magnitude 9.5. Its focus extended along Atakama deep basin - roughly from Concepcion to Chiloe Island. After that the series of weaker earthquakes swept down to Tierra del Fuego. The earthquake was preceded by a foreshock series, which began on May 21, 1960. Shortly after the main shock tide, it was replaced by the terrible tsunami. Several giant waves rolled on the Chilean coast. The first surge of the sea was small, about 4-5 meters above the normal level, and the sea remained stationary for about 5 minutes. Then it began retreating rapidly with a terrible noise, like the sound of the intake water. The second wave height up to 8 m came in 20 minutes. The sea was high for 10-15 minutes, and then retreated. The third wave came an hour later. It was higher than the second, reaching 10-11 m, and its velocity reached 100 km / h. Moving the wreckage of houses, piled up by the second wave, the sea once again sank a quarter of an hour, and then began to retreat with a terrible metallic sound. After that the wave moved in the opposite direction and almost with the same destructive force struck the coast of Japan, killing 150 people there, destroyed six thousand and flooded about 40 thousand houses. It was the largest of the officially recorded earthquakes. More than 10 thousand dead, 2 million homeless in the southern regions of Chile. The height of tsunami waves near the epicenter was 25 meters. The devastating earthquake on May 22 generated tsunami waves that spread across the Pacific and beyond at the speed of 650-700 km / hr. At the Chilean coast there were destroyed fishing villages and port facilities, hundreds of people were washed away by the waves. Then tsunami reached the Hawaiian Islands. This wave height was about 10 meters and destruction was strong. Apartment buildings, office buildings, cars were washed away or destroyed. The number of victims of this tsunami was 60 people. Swept across the entire Pacific Ocean, the giant waves struck on Japan. At the Japanese islands there were flooded 36 000 houses, overturned 900 ships and fishing boats. Never before it was observed that the tsunami waves, breaking such a large distance, kept their destructive force. In the morning of May 24 tsunami went to the Pacific coast of the Far East of Russia. Lifting height of water in the average was 3-4 m, the maximum reached about 6-7 meters in the region of Kuril Islands, the maximum height of water was 4,7 m in the vicinity of the North Kuriles. Houses, warehouses and wharf were flooded at the coast. The wave washed away the bridge and some buildings in Yuzhno-Kurilsk. In the region of Malokurilsk, where the height of lifting water reached 4 meters, there were submerged piers and some of the buildings, the bridge was washed up above the land level and ships were torn from their anchors. This tsunami was observed on all the islands of the Kuril Ridge. Maximum lifting height of water was 4 m at Shikotan Island, 2,2 m at Kunashir Island, 2,5 m at Iturup Island, 1,3-1,5 m at Matua Island. The tsunami penetrated to Okhotsk Sea. In Magadan lifting height of water was 2.2 m. The weak tsunami was also observed in Sakhalin.
    Focal mechanism and seismic moment of the earthquake
         Table 2 and Figure 6 present focal mechanism solution, which was obtained by the CMT method in the National Earthquake Information Center of the U.S. Geological Survey (USGS) for the earthquake, which happened on February 27, 2010 at 06:34 a.m. GMT. This earthquake occurred under the action of rather equal expansion and compressive forces oriented in W-E direction. One nodal plane NP2 was fairly steep (the angle of inclination DP = 75 º), it was propagating almost along meridian (STK = 181 º), another plane NP1 was laying flat with N-E direction of propagation (STK = 16 º). The type of motion for the NP2 plane was uplift with left-hand shift components, while for the NP1 plane it was the thrust with right-hand shift components. The value of the seismic moment Mo for the earthquake on Feb. 26, 2010 according to the USGS was 3.4 * 10 ** 22 n * m, the value of moment magnitude Mw = 8.8.
    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
    598630274 31821614104181 7586NEIC
  • NEIC - National Earthquakes Information Center of US Geological Service

    • Figure 6


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