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Posts Tagged ‘Sibolga’

Powerful Earthquake Strikes N. Sumatra, Indonesia

Posted by feww on April 6, 2010

Serial No  1,542. If any posts are blocked in your country, please drop us a line.

Powerful earthquake measuring up to 7.9Mw strikes northern Sumatra, Indonesia

The quake struck at a depth of about 46km (28.6 miles) on April 06, 2010 at 22:15:02UTC about 205 km (125 miles) WNW of Sibolga, Sumatra, Indonesia. The epicenter was located at 2.236°N, 97.046°E.

The quake struck about 160km southeast of the magnitude 9.1 quake which triggered the destructive Boxing Day tsunami in 2004.

The epicenter was also about 34km NNW of the a magnitude 8.6 shock which occurred on March 28, 2005.

A magnitude 7.6 quake in West Sumatra in September 2009 killed 1,000 people, official records showed.

Tsunami Evaluation

The following bulletin was issued by the PACIFIC TSUNAMI WARNING CENTER/NOAA/NWS a short time ago:

SEA LEVEL READINGS INDICATE A TSUNAMI WAS GENERATED. IT MAY HAVE BEEN DESTRUCTIVE ALONG COASTS NEAR THE EARTHQUAKE EPICENTER. FOR THOSE AREAS – WHEN DAMAGING WAVES HAVE NOT OCCURRED FOR AT LEAST TWO HOURS THEN LOCAL AUTHORITIES CAN ASSUME THE THREAT IS PASSED. DANGER TO BOATS AND COASTAL STRUCTURES CAN CONTINUE FOR SEVERAL HOURS DUE TO RAPID CURRENTS.  AS LOCAL CONDITIONS CAN CAUSE A WIDE VARIATION IN TSUNAMI WAVE ACTION THE ALL CLEAR DETERMINATION
MUST BE MADE BY LOCAL AUTHORITIES.

NO TSUNAMI THREAT EXISTS FOR OTHER COASTAL AREAS IN THE INDIAN OCEAN ALTHOUGH SOME OTHER AREAS MAY EXPERIENCE SMALL SEA LEVEL CHANGES AND STRONG OR UNUSUAL COASTAL CURRENTS.

ESTIMATED INITIAL TSUNAMI WAVE ARRIVAL TIMES AT FORECAST POINTS WITHIN THE WARNING AND WATCH AREAS ARE GIVEN BELOW. ACTUAL ARRIVAL TIMES MAY DIFFER AND THE INITIAL WAVE MAY NOT BE THE LARGEST. A TSUNAMI IS A SERIES OF WAVES AND THE TIME BETWEEN SUCCESSIVE WAVES CAN BE FIVE MINUTES TO ONE HOUR.

LOCATION         FORECAST POINT     COORDINATES     ARRIVAL TIME
———————————————————————————————————
INDONESIA        SIMEULUE 2.5N  96.0E            22:46UTC 06 APR
+++++++++++BELAWAN 3.8N  98.8E            02:33UTC 07 APR

ADDITIONAL BULLETINS WILL BE ISSUED BY THE PACIFIC TSUNAMI  WARNING CENTER FOR THIS EVENT AS MORE INFORMATION BECOMES AVAILABLE.

THE JAPAN METEOROLOGICAL AGENCY MAY ISSUE ADDITIONAL INFORMATION FOR THIS EVENT. IN THE CASE OF CONFLICTING INFORMATION…THE MORE CONSERVATIVE  INFORMATION SHOULD BE USED FOR SAFETY.

There was no report of damage or casualties, as of posting.  However, a major power blackout on Simeulue Island, west of Aceh province, Indonesia, has been reported.

Updates will posted in the comments section of this post.

Earthquake Details:

  • Magnitude [USGS Estimate] 7.8
  • Date-Time:
    • Tuesday, April 06, 2010 at 22:15:02 UTC
    • Wednesday, April 07, 2010 at 05:15:02 AM at epicenter
  • Location: 2.236°N, 97.046°E
  • Depth: 46 km (28.6 miles)
  • Region: NORTHERN SUMATRA, INDONESIA
  • Distances:
    • 205 km (125 miles) WNW of Sibolga, Sumatra, Indonesia
    • 230 km (145 miles) SW of Medan, Sumatra, Indonesia
    • 525 km (325 miles) W of KUALA LUMPUR, Malaysia
    • 1425 km (880 miles) NW of JAKARTA, Java, Indonesia
  • Location Uncertainty: horizontal +/- 7.4 km (4.6 miles); depth +/- 11.6 km (7.2 miles)
  • Source: USGS NEIC (WDCS-D)
  • Event ID: us2010utc5

Seismotectonics of the Indonesian Region

Tectonics Plates The Indonesian region is one of the most seismically active zones of the earth; at the same time it has a leading position from the point of view of active and potentially active volcanoes. It is a typical island-arc structure with its characteristic physiographic features, such as a deep oceanic trench, a geanticline belt, a volcanic inner arc and a marginal basin.

In most subduction zones, motion of the subducted plate is nearly perpendicular to the trench axis. In some cases, for example Sumatra, where the motion is oblique to the axis, a strike-slip fault zone is seen, and is lying parallel to the volcanic chain.

In the subduction zone southwest of Sumatra, the Sunda trench axis strikes approximately N 37°W. The Indian Ocean crust is moving in an azimuth of approximately N 23°E relative to Southeast Asia, giving an angle of obliquity of 60°. Eastern Indonesia, forming the southeastern extremity of the Southeast Asian lithospheric plate, crushed between the northward-moving Indo-Australian and the westward-moving Pacific plates, is certainly the most complex active tectonic zone on earth. The rate of subduction is some centimeters per year; for example, it is 6.0 cm per year in the West Java Trench at 0°S 97°E (azimuth 23°); 4.9 cm per year in the East Java Trench at 12°S 120°E (azimuth 19°); and 10.7 cm per year in New Guinea at 3°S 142°E (azimuth 75°).

Frequent volcanic eruptions and frequent earthquake shocks testify to the active tectonic processes which are currently in progress in response to the continued movement of these major plates. The distribution of small ocean basins, continental fragments, remnants of ancient magmatic arcs and numerous subduction complexes which make up the Indonesian region indicate that the past history of the region was equally tectonically active.

Abridged from Southeast Asia Association of Seismology and Earthquake Engineering, Series on Seismology, Volume V – Indonesia, June 1985. (Source: USGS/EHP)

Maps

Related Links:

Historic Earthquakes in Indonesia


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